Update README.md

Reviewed-on: #19

Makefile

@@ -1,33 +1,60 @@
-SOURCES = src/debug/misc.c src/io/term/flanterm_backends/fb.c src/io/term/flanterm.c src/debug/panic.c src/debug/stacktrace.c src/boot/boot.c src/sched/scheduler.c src/sched/process.c src/mem/heap/kheap.c src/mem/paging/vmm.c src/mem/paging/paging.c src/mem/paging/pmm.c src/string/string.c src/io/kbd/ps2.c src/io/serial/serial.c src/io/term/printf.c src/io/term/term.c src/idt/idt.c src/mem/gdt/gdt.c src/mem/misc/utils.c src/time/timer.c src/kmain.c
+USER_PROGRAMS := pedicel.raw apex.raw
+USER_FILES := wow.txt
 
-CC_FLAGS=-Wall -Wextra -std=gnu99 -nostdlib -ffreestanding -fno-stack-protector -fno-omit-frame-pointer -fno-stack-check -fno-PIC -ffunction-sections -fdata-sections -mcmodel=kernel
+BUILDDIR := build
-CC_PROBLEMATIC_FLAGS=-Wno-unused-parameter -Wno-unused-variable
+ELFFILE := pepperk
+SRC := src
 
-.PHONY: build build-iso debug debug2 run clean
+CC_PROBLEMATIC_FLAGS:=-Wno-unused-parameter -Wno-unused-variable
 
-build:
+ifeq ($(UBSAN),true)
-	mkdir -p build
+SOURCES := $(shell find src -name '*.c')
-	rm -f *.o build/*.o
+CC_PROBLEMATIC_FLAGS:= -fsanitize=undefined
-	x86_64-elf-gcc -g -c -Isrc $(SOURCES) $(CC_PROBLEMATIC_FLAGS) $(CC_FLAGS)
+else
-	mv *.o build/
+SOURCES := $(shell find src -name '*.c')
-	nasm -f elf64 src/idt/idt.S -o build/idt_stub.o
+SOURCES := $(filter-out src/security/ubsan.c, $(SOURCES))
-	x86_64-elf-ld -o pepperk -T linker.ld build/*.o
+endif
-	nm -n pepperk | awk '$$2 ~ /[TtDdBbRr]/ {print $$1, $$3}' > symbols.map
+
+OBJFILES := $(patsubst $(SRC)/%.c, $(BUILDDIR)/%.o, $(SOURCES))
+
+CC := x86_64-elf-gcc
+CC_FLAGS=-Wall -Wextra -std=gnu99 -nostdlib -ffreestanding -fstack-protector -fno-omit-frame-pointer -fno-stack-check -fno-PIC -ffunction-sections -fdata-sections -mcmodel=kernel -mno-red-zone
+
+LD := x86_64-elf-ld
+
+$(ELFFILE): $(BUILDDIR) $(OBJFILES)
+	nasm -f elf64 src/arch/x86/idt.S -o $(BUILDDIR)/idt_stub.o
+	$(LD) -o $(ELFFILE) -T linker.ld $(OBJFILES) $(BUILDDIR)/idt_stub.o
+	# Get the symbols for debugging
+	nm -n $(ELFFILE) | awk '$$2 ~ /[TtDdBbRr]/ {print $$1, $$3}' > symbols.map
 	python3 symbols.py
-	nasm -f elf64 symbols.S -o build/symbols.o
+	nasm -f elf64 symbols.S -o $(BUILDDIR)/symbols.o
-	x86_64-elf-ld -o pepperk -T linker.ld build/*.o
+	$(LD) -o $(ELFFILE) -T linker.ld $(OBJFILES) $(BUILDDIR)/idt_stub.o $(BUILDDIR)/symbols.o
+
+$(BUILDDIR):
+	@mkdir -p $(BUILDDIR)
+
+$(BUILDDIR)/%.o: $(SRC)/%.c
+	mkdir -p $(dir $@)
+	$(CC) -g -c -Iinclude $< $(CC_PROBLEMATIC_FLAGS) $(CC_FLAGS) -o $@
 
 limine/limine:
 	rm -rf limine
 	git clone https://github.com/limine-bootloader/limine.git --branch=v9.x-binary --depth=1
 	$(MAKE) -C limine
 
-build-iso: limine/limine build
+.PHONY: user
+user:
+	$(MAKE) -C user
+	tar cvf $(BUILDDIR)/initfs.tar -C $(BUILDDIR) $(USER_PROGRAMS) -C ../user $(USER_FILES)
+
+build-iso: limine/limine $(ELFFILE)
 	rm -rf iso_root
 	mkdir -p iso_root/boot
-	cp -v pepperk iso_root/boot
+	cp -v $(ELFFILE) iso_root/boot
 	mkdir -p iso_root/boot/limine
 	cp -v limine.conf iso_root/boot/limine
+	cp $(BUILDDIR)/initfs.tar iso_root/boot/
 	mkdir -p iso_root/EFI/BOOT
 	cp -v limine/limine-bios.sys limine/limine-bios-cd.bin limine/limine-uefi-cd.bin iso_root/boot/limine/
 	cp -v limine/BOOTX64.EFI iso_root/EFI/BOOT/
@@ -39,16 +66,20 @@ build-iso: limine/limine build
 		iso_root -o pepper.iso
 	./limine/limine bios-install pepper.iso
 
+.PHONY: debug
 debug:
 	/usr/bin/qemu-system-x86_64 -drive file=pepper.iso -s -S -d int -D qemu.log -no-reboot -no-shutdown &
-	gdb pepperk --command=debug.gdb
+	gdb $(ELFFILE) --command=debug.gdb
 
+.PHONY: debug2
 debug2:
 	/usr/bin/qemu-system-x86_64 -drive file=pepper.iso -s -S -d int -no-reboot -no-shutdown &
-	pwndbg pepperk --command=debug.gdb
+	pwndbg $(ELFFILE) --command=debug.gdb
 
+.PHONY: run
 run: build-iso
 	/usr/bin/qemu-system-x86_64 -cdrom pepper.iso -serial stdio
 
+.PHONY: clean
 clean:
-	rm -rf *.o symbols.map symbols.S pepperk iso_root pepper.iso limine build/*.o
+	rm -rf $(BUILDDIR) symbols.map symbols.S $(ELFFILE) iso_root pepper.iso limine

README.md

@@ -1,50 +1,64 @@
 # <img width="40" height="40" alt="red-pepper" src="https://i.ibb.co/mrHH6d1m/pixil-frame-0-4.png" /> pepperOS: "will never be done"
+<a href="https://ibb.co/KxbfxmFB"><img src="https://i.ibb.co/GQn8QFcG/pepper.png" alt="pepper" border="0"></a>
+## Description
 
-## Trying the kernel
+PepperOS is a 64-bit freely-licensed monolithic kernel for x86 processors, with round-robin preemptive scheduling and 4-level paging. See the [manual](docs/MANUAL.md) for more.
 
-First install the dependencies: `sudo apt install python3 xorriso make qemu-system`
+## Trying the kernel in QEMU
 
-Also, you have to get an x86_64 toolchain for compilation. The easiest way to do that on most systems is to install it from Homebrew:
+### Debian-based distributions
+
+First, install the dependencies: `sudo apt install nasm python3 xorriso make qemu-system`
+
+Then, you can get an x86_64 toolchain for compilation. The easiest way to do that on most systems is to install it from Homebrew:
 
 ```
 brew install x86_64-elf-gcc
 ```
 
-Then, to compile the kernel and make an ISO image file: `make build-iso`
+If you're already on a 64-bit machine (which you probably are), and don't want to install a cross-compiler, you can just override `CC` and `LD` variables in the Makefile, like so:
-To run it with QEMU, `make run`
 
-## TODO
+```
+CC := gcc
+LD := ld
+```
 
-The basics that I'm targeting are:
+Then, to compile the kernel and make an ISO image file, run: `make`.  
+To build the user programs and the initial filesystem, do `make user`.  
+To run it with QEMU, do: `make run`.  
 
-### Basic utility of what we call a "kernel"
+## Trying the kernel on real hardware
 
-- Implement tasks, and task switching + context switching and spinlock acquire/release
+Compile the kernel and generate an ISO image like described above, then burn the image to a USB stick, `/dev/sdX` being the device name (you can get it using `lsblk`):
-- Load an executable
-- Filesystem (TAR for read-only initfs, then maybe read-write using FAT12/16/32 or easier fs) w/ VFS layer
-- Getting to userspace (ring 3 switching, syscall interface)
-- Porting musl libc or equivalent
 
-### Scalability/maintenance/expansion features
+```
+sudo dd if=pepper.iso of=/dev/sdX
+```
 
-- Documentation
+## Compilation options
-- SOME error handling in functions
-- Unit tests
-- Good error codes (like Linux kernel: ENOMEM, ENOENT, ...)
 
-### Optional features
+By default, PepperOS is compiled without the following features:
 
-In the future, maybe?
+```
-- SMP support (Limine provides functionality to make this easier)
+UBSAN - undefined behavior sanitization
-- Parsing the ACPI tables and using them for something
+```
-- Replacing the PIT timer with APIC
+
+These features can be activated by setting them to "true" at the end of the make command, for example:
+
+```
+make UBSAN=true
+```
+
+## Writing software for PepperOS
+
+If you want to write software for PepperOS, take a look at the [Software Developer's guide](docs/SOFTWARE.md).
 
 ## Thanks
 
 PepperOS wouldn't be possible without the following freely-licensed software:
 
 - the [Limine](https://codeberg.org/Limine/Limine) portable bootloader
-- Marco Paland's freestanding [printf implementation](https://github.com/mpaland)
+- Charles Nicholson's [nanoprintf](https://github.com/charlesnicholson/nanoprintf)
 - Mintuski's [Flanterm](https://codeberg.org/Mintsuki/Flanterm) terminal emulator
 
 ...and without these amazing resources:
@@ -52,3 +66,6 @@ PepperOS wouldn't be possible without the following freely-licensed software:
 - the [OSDev](https://osdev.org) wiki & forums
 - Intel 64 and IA-32 Architectures Software Developer's Manual
 - Documentation for the [GNU Compiler Collection](https://gcc.gnu.org/onlinedocs/gcc/)
+- dreamos82's [OSDev Notes](https://github.com/dreamportdev/Osdev-Notes/tree/master)
+- the [Sortix UBsan hook implementations](https://gitlab.com/sortix/sortix/-/blob/main/libc/ubsan/ubsan.c)
+- the [CSC 395](https://curtsinger.cs.grinnell.edu/teaching/2022S/CSC395/kernel/) Kernel Development course from Grinnell College

docs/MANUAL.md

@@ -0,0 +1,52 @@
+# PepperOS Manual
+
+# Table of Contents
+
+- [Overview](#i-overview)
+    - [Supported Hardware](#a-supported-hardware)
+    - [Features](#b-features)
+- [Kernel architecture](#ii-kernel-architecture)
+    - [Boot process](#a-boot-process)
+    - [Memory management](#b-memory-management)
+    - [Scheduling](#c-scheduling)
+    - [Input/output](#d-inputoutput)
+- [Syscall table](#iii-syscall-table)
+
+## I. Overview
+
+## a. Supported Hardware
+
+The recommended hardware to run PepperOS is the following:
+
+- UEFI/BIOS
+- Any x86 processor, 64-bits only
+- PS/2 Keyboard
+- Minimum 128MB of memory
+
+## b. Features
+
+- Round robin preemptive scheduling
+- Coexistence of ring 0 and ring 3 processes
+
+## II. Kernel architecture
+
+### a. Boot process
+
+### b. Memory management
+
+### c. Scheduling
+
+### d. Input/Output
+
+## III. Syscall table
+
+The syscall interface in the Pepper kernel uses the System V ABI convention for argument order.
+It vaguely mimics Unix-like systems.
+
+Name | Number (%rax) | arg0 (%rdi) | arg1 (%rsi) | arg2 (%rdx) |
+|---|---|---|---|---|
+| sys_read | 0 | unsigned int fd | char* buf | size_t count |
+| sys_write | 1 | unsigned int fd | const char* buf | size_t count |
+| sys_open | 2 | const char* filename | int flags | |
+| sys_close | 3 | unsigned int fd | | |
+| sys_exit | 60 | int error_code | | |

docs/SOFTWARE.md

@@ -0,0 +1,57 @@
+# Writing software for PepperOS
+
+## Why would you want to do that?
+
+Honestly I have no idea. Maybe you have too much free time.  
+Keep in mind that the Pepper kernel is a personal project and it's full of bugs, inconsistencies, weird ways of doing things (and I don't care because it's my toy).  
+Now if you still want to write something for this OS, thank you. Follow along.
+
+## 1. Write the source code
+
+PepperOS is able to run programs written in x86 assembly, and C programs.
+
+### x86 Assembly
+
+Start your assembly file with the `bits 64` instruction, to emit 64-bit code.  
+You can add sections `.text`, `.data`, `.bss` as you need.  
+The three things to take in consideration here are:
+- PepperOS does not use the `syscall` instruction, instead it uses the old-fashioned `int 0x80` to trigger a system call.  
+- The entry point should be labelled as `_start`.
+- At the end of the file, there should be an exit system call followed by a loop, like so:
+
+```nasm
+.end:
+    mov rax, 0x3C
+    mov rdi, 0x0
+    int 0x80
+
+.loop:
+    jmp .loop
+```
+
+For an example, look at the file [pedicel.S](../user/pedicel.S).
+
+### C program
+
+You will find relevant headers in the `libc` directory. They contain system call wrappers, utility functions, and more. See what's implemented there and what's not.  
+To invoke a system call you can use the functions defined in `libc/syscall.h`.
+
+## 2. Add the Makefile rule and variable
+
+Now that your code is complete, add a Makefile rule to `user/Makefile` with your program name. You can just copy-paste the rule that applies to you (either from an Assembly source or C source) and change the name of the files (.raw, .elf, etc...) in the rule.  
+For clarity, raw binaries have the `.raw` extension, and ELF ones have `.elf`.  
+You also now have to add the name of the executable to the `USER_PROGRAMS` variable at the top of the global Makefile.  
+Finally, do `make user` to compile your program.
+
+## 3. Run your program
+
+You can now boot up PepperOS, in a VM or on real hardware, and use the kernel's shell to `list` files in the filesystem (to see if your executable was properly added), and then, run it with the `load` command. Congratulations, you made a program for a random hobby OS!
+
+## 4. (Optional) debugging
+
+Use GDB with the `make debug` rule!  
+For your information, user programs are loaded at `0x400000`. Can be good to know to set breakpoints.
+
+## 5. (Optional) contribute!
+
+If you like what you've done and you think it could be nice to add it to PepperOS, send it to me by e-mail: `xamidev (at) riseup (dot) net`. It may or may not be added in a future release... who knows?

docs/STYLE.md

@@ -2,6 +2,14 @@
 
 This document describes the coding style for the Pepper kernel. It is used as a guideline across all source files.
 
+## Setting up a language server (optional)
+
+Before you do anything you might want to setup a language server with your editor. This will save you lots of time correcting errors and stuff. I use `clangd`, and generate my `compile_commands.json` like so:
+
+```
+bear -- make
+```
+
 ## Indentation
 
 Indentations should be 4 characters long.

include/arch/gdt.h

@@ -1,6 +1,6 @@
 /*
  * @author  xamidev <xamidev@riseup.net>
- * @brief   Global Descriptor Table (for legacy reasons)
+ * @brief   Global Descriptor Table
  * @license GPL-3.0-only
  */
 
@@ -13,19 +13,32 @@
 // we'll only use this as a requirement for paging, not more.
 // This means base 0 and no limit (whole address space)
 
-#define NUM_GDT_ENTRIES 5
+#define NUM_GDT_ENTRIES 7
 
 #define NULL_SELECTOR 0x00
 #define KERNEL_CODE_SEGMENT 0x08
 #define KERNEL_DATA_SEGMENT 0x10
 #define USER_CODE_SEGMENT 0x18
 #define USER_DATA_SEGMENT 0x20
+#define TSS_SEGMENT 0x28
 
 struct GDTR {
     uint16_t limit;
     uint64_t address;
 } __attribute__((packed));
 
+struct tss {
+    uint32_t reserved0;
+    uint64_t rsp0;
+    uint64_t rsp1;
+    uint64_t rsp2;
+    uint64_t reserved1;
+    uint64_t ist[7];
+    uint64_t reserved2;
+    uint16_t reserved3;
+    uint16_t iopb;
+} __attribute__((packed));
+
 void gdt_init(void);
 
 #endif

include/arch/x86.h

@@ -1,14 +1,20 @@
-/*
+#ifndef X86_H
- * @author  xamidev <xamidev@riseup.net>
+#define X86_H
- * @brief   Interrupt Descriptor Table setup and dispatching
- * @license GPL-3.0-only
- */
-
-#ifndef IDT_H
-#define IDT_H
 
+#include <stdbool.h>
 #include <stdint.h>
 
+uint64_t rdmsr(uint32_t msr);
+void cpuid(uint32_t leaf, uint32_t* eax, uint32_t* ebx, uint32_t* ecx, uint32_t* edx);
+void wrmsr(uint32_t msr, uint64_t value);
+bool x86_has_msr();
+void x86_arch_init();
+
+void x86_cpu_identification();
+int cpuid_get_vendor_string(char* str);
+
+/* Interrupt Descriptor Table */
+
 void idt_init(void);
 
 struct interrupt_descriptor {
@@ -29,7 +35,7 @@ struct idtr {
 // All general-purpose registers (except rsp) as stored on the stack,
 // plus the values we pushed (vector number, error code) and the iret frame
 // In reverse order because the stack grows downwards.
-struct cpu_status_t {
+struct cpu_status {
     uint64_t r15;
     uint64_t r14;
     uint64_t r13;
@@ -56,4 +62,6 @@ struct cpu_status_t {
     uint64_t iret_ss;
 };
 
+struct cpu_status* syscall_handler(struct cpu_status* regs);
+
 #endif

include/boot/boot.h

@@ -0,0 +1,14 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Boot routines
+ * @license GPL-3.0-only
+ */
+
+#ifndef BOOT_H
+#define BOOT_H
+
+#include <kernel.h>
+
+void populate_boot_context(struct boot_context* boot_ctx);
+
+#endif

include/config.h

@@ -0,0 +1,70 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   PepperOS configuration file
+ * @license GPL-3.0-only
+ */
+
+#ifndef CONFIG_H
+#define CONFIG_H
+
+/* version */
+#define PEPPEROS_VERSION_MAJOR "0"
+#define PEPPEROS_VERSION_MINOR "1"
+#define PEPPEROS_VERSION_PATCH "121"
+#define PEPPEROS_SPLASH \
+"\x1b[38;5;196m                                      \x1b[38;5;231m____  _____\r\n\x1b[0m"\
+"\x1b[38;5;196m    ____  ___  ____  ____  ___  _____\x1b[38;5;231m/ __ \\/ ___/\r\n\x1b[0m"\
+"\x1b[38;5;196m   / __ \\/ _ \\/ __ \\/ __ \\/ _ \\/ ___\x1b[38;5;231m/ / / /\\__ \\ \r\n\x1b[0m"\
+"\x1b[38;5;196m  / /_/ /  __/ /_/ / /_/ /  __/ /  \x1b[38;5;231m/ /_/ /___/ / \r\n\x1b[0m"\
+"\x1b[38;5;196m / .___/\\___/ .___/ .___/\\___/_/   \x1b[38;5;231m\\____//____/  \r\n\x1b[0m"\
+"\x1b[38;5;196m/_/        /_/   /_/                             \r\n\x1b[0m"\
+"     --- version \x1b[38;5;220m"PEPPEROS_VERSION_MAJOR"."PEPPEROS_VERSION_MINOR"."PEPPEROS_VERSION_PATCH"\x1b[0m built on \x1b[38;5;40m"__DATE__" "__TIME__"\x1b[0m\r\n"
+
+/* pedicel */
+#define PEDICEL_PROMPT "pedicel$ "
+#define PEDICEL_INPUT_SIZE 128
+
+/* process */
+#define PROCESS_NAME_MAX 64
+#define PROCESS_STACK_SIZE 0x10000 // 64kb
+#define PROCESS_STACK_TOP 0x80000000
+
+/* sched */
+// 1 tick = 1 ms => quantum = 10ms
+#define SCHEDULER_QUANTUM 10
+
+/* kernel */
+#define KERNEL_BASE 0xFFFFFFFF80000000ULL
+// 2 MB should be enough (as of now, the whole kernel ELF is around 75kb)
+#define KERNEL_SIZE 0x200000
+#define KERNEL_STACK_SIZE 65536
+#define KERNEL_IDT_ENTRIES 33
+
+/* user */
+#define USER_STACK_TOP 0x80000000
+#define USER_STACK_PAGES 16 // 16*4096 = 64kb
+#define USER_CODE_START 0x400000 // like linux
+
+/* paging */
+#define PAGING_MAX_PHYS 0x200000000
+
+/* heap */
+#define KHEAP_SIZE (32*1024*1024)
+
+/* term */
+#define TERM_HISTORY_MAX_LINES 256
+
+/* kbd */
+#define KBD_BUFFER_MAX 256
+
+/* time */
+#define TIMER_FREQUENCY 1000
+
+/* ssp */
+#define STACK_CHK_GUARD 0x7ABA5C007ABA5C00
+
+/* fs */
+#define FDT_MAX 8 // Maximum amount of file descriptors per process
+
+
+#endif

include/fs/initfs.h

@@ -0,0 +1,18 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   PS/2 Keyboard driver
+ * @license GPL-3.0-only
+ */
+
+#ifndef INITFS_H
+#define INITFS_H
+
+#include <limine.h>
+
+int initfs_init(struct limine_file* tar_file);
+int tar_lookup(unsigned char* archive, char* filename, char** out);
+int tar_exists(const char* filename);
+int tar_read(char* filename, char* out, int count, int offset);
+void tar_list();
+
+#endif

include/io/kbd/ps2.h

@@ -7,7 +7,12 @@
 #ifndef PS2_H
 #define PS2_H
 
+#include <stddef.h>
+
 void keyboard_handler(void);
+char keyboard_getchar();
+int keyboard_putchar(char c);
+int keyboard_getline(char* output, size_t size);
 
 #define SHIFT_PRESSED_BIT 0b00000001
 #define ALT_PRESSED_BIT   0b00000010

include/io/term/term.h

@@ -8,7 +8,9 @@
 #define TERM_H
 
 void kputs(const char* str);
-void _putchar(char character);
 void term_init(void);
+int printf(const char* fmt, ...);
+void internal_putc(int c, void *_);
+int kprintf(const char* fmt, ...);
 
 #endif

include/kernel.h

@@ -7,43 +7,52 @@
 #ifndef KERNEL_H
 #define KERNEL_H
 
+#include "limine.h"
+
 enum ErrorCodes {
-	ENOMEM,
+	ENOMEM, // No memory
-	EIO
+	EIO,    // Input/output error
+	ENOENT, // No entry
+	EBADFD,  // Bad file descriptor
+	EMFILE,  // Too many open files
+	EINVAL  // Invalid argument
 };
 
 #define CLEAR_INTERRUPTS __asm__ volatile("cli")
 #define SET_INTERRUPTS __asm__ volatile("sti")
 
-#include "io/serial/serial.h"
+#include <io/serial/serial.h>
-#include "io/term/printf.h"
+#include <io/term/term.h>
-#include "idt/idt.h"
+#include <arch/x86.h>
 #include <stdbool.h>
 
 extern volatile uint64_t ticks;
-
+#define DEBUG(log, ...) kprintf("[%8u] debug: <%s>: " log "\r\n", ticks, __func__, ##__VA_ARGS__)
-#define DEBUG(log, ...) fctprintf((void*)&skputc, 0, "[%8u] debug: <%s>: " log "\r\n", ticks, __func__, ##__VA_ARGS__)
 
 /* #define DEBUG(log, ...) \
 	printf("debug: [%s]: " log "\r\n", __FILE__, ##__VA_ARGS__); \
 	fctprintf((void*)&skputc, 0, "debug: [%s]: " log "\r\n", __FILE__, ##__VA_ARGS__)
  */
 
-#define DIE_DEBUG(str) fctprintf((void*)&skputc, 0, str)
+#define DIE_DEBUG(str) printf(str)
 
 #define CHECK_BIT(var,pos) ((var) & (1<<(pos)))
 
 // printf("debug: [%s]: " log "\n", __FILE__, ##__VA_ARGS__);
 
-void panic(struct cpu_status_t* ctx, const char* str);
+void panic(struct cpu_status* ctx, const char* str);
 void hcf(void);
 void idle(void);
 
+void pedicel_main(void* arg);
+
 /* debug */
 void debug_stack_trace(unsigned int max_frames);
 const char* debug_find_symbol(uintptr_t rip, uintptr_t* offset);
 void boot_mem_display(void);
 
+int loader_load_raw();
+
 #define assert(check) do { if(!(check)) hcf(); } while(0)
 
 struct boot_context {
@@ -51,6 +60,8 @@ struct boot_context {
 	struct limine_memmap_response* mmap;
 	struct limine_hhdm_response* hhdm;
 	struct limine_kernel_address_response* kaddr;
+	struct limine_boot_time_response* bootdate;
+	struct limine_module_response* module;
 };
 
 // Are these modules initialized yet?
@@ -59,6 +70,7 @@ struct init_status {
 	bool serial;
 	bool keyboard;
 	bool timer;
+	bool all;
 };
 
 #endif

include/mem/kheap.h

@@ -16,11 +16,11 @@
 #include <stddef.h>
 #include <stdint.h>
 
-struct heap_block_t {
+struct heap_block {
     size_t size;
     bool free; // 1byte
     uint8_t reserved[7]; // (7+1 = 8 bytes)
-    struct heap_block_t* next;
+    struct heap_block* next;
 } __attribute__((aligned(16)));
 
 void kheap_init(void);
@@ -28,5 +28,6 @@ void* kmalloc(size_t size);
 void kfree(void* ptr);
 void* kalloc_stack(void);
 void kheap_map_page(void);
+void kheap_info();
 
 #endif

include/mem/paging.h

@@ -11,14 +11,16 @@
 
 #include <stdint.h>
 #include <limine.h>
-#include "mem/heap/kheap.h"
+#include <mem/kheap.h>
 #include <kernel.h>
 
 void paging_init(struct boot_context boot_ctx);
 void paging_map_page(uint64_t* root_table, uint64_t virt, uint64_t phys, uint64_t flags);
+uint64_t* alloc_page_table();
 
 // To swap root page tables
 void load_cr3(uint64_t value);
+void invlpg(void *addr);
 
 extern uint64_t hhdm_off;
 
@@ -32,7 +34,7 @@ extern uint64_t hhdm_off;
 #define PAGE_ALIGN_DOWN(x) ((x) & PTE_ADDR_MASK)
 
 #define ALIGN(size) ALIGN_UP(size, 16)
-#define BLOCK_MIN_SIZE (sizeof(struct heap_block_t) + 16)
+#define BLOCK_MIN_SIZE (sizeof(struct heap_block) + 16)
 
 #define PML4_INDEX(x) (((x) >> 39) & 0x1FF)
 #define PDPT_INDEX(x) (((x) >> 30) & 0x1FF)

include/mem/utils.h

@@ -8,6 +8,7 @@
 #define MEM_UTILS_H
 
 #include <stddef.h>
+#include <limine.h>
 
 void* memcpy(void* restrict dest, const void* restrict src, size_t n);
 void* memset(void* s, int c, size_t n);

include/mem/vmm.h

@@ -0,0 +1,31 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Virtual memory manager
+ * @license GPL-3.0-only
+ */
+
+#ifndef VMM_H
+#define VMM_H
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+
+struct vmm_context {
+    uint64_t* pml4;
+};
+
+void vmm_init(void);
+void* vmm_alloc_region(uint64_t* pml4, size_t pages, uint64_t flags);
+bool vmm_is_mapped(uint64_t* pml4, uint64_t virt);
+void vmm_unmap(uint64_t* pml4, uint64_t virt);
+void* vmm_map(uint64_t* pml4, uint64_t virt, uint64_t flags);
+uint64_t* vmm_create_address_space();
+uint64_t vmm_virt_to_phys(uint64_t* pml4, uint64_t virt);
+uintptr_t vmm_alloc_user_stack(uint64_t* pml4);
+uintptr_t vmm_alloc_user_code(uint64_t* pml4, void* code_addr, uint64_t code_size);
+
+#define VMM_USER_SPACE_START 0x0000000000001000 
+#define VMM_USER_SPACE_END   0x00007FFFFFFFF000
+
+#endif

include/sched/process.h

@@ -0,0 +1,56 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Process definition
+ * @license GPL-3.0-only
+ */
+
+#ifndef PROCESS_H
+#define PROCESS_H
+
+#include <stddef.h>
+#include <config.h>
+#include <stdint.h>
+#include <limine.h>
+#include <stdbool.h>
+
+typedef enum {
+    READY,
+    RUNNING,
+    DEAD
+} status_t;
+
+struct fd {
+    int fd;
+    char filename[PROCESS_NAME_MAX];  // File opened
+    uint64_t cursor; // Cursor position in file
+    bool open;
+};
+
+struct process {
+    size_t pid;
+    char name[PROCESS_NAME_MAX];
+
+    status_t status;
+    struct cpu_status* context;
+	void* root_page_table; // Process PML4 (should contain kernel PML4 in higher half [256-511]
+    void* kernel_stack; // Used for interrupts (syscall: int 0x80), defines the TSS RSP0
+    
+    struct fd fdt[FDT_MAX]; // File Descriptor Table
+    size_t next_free_fd;
+    
+    struct process* next;
+};
+
+void process_init(void);
+struct process* process_create(char* name, void(*function)(void*), void* arg);
+void process_add(struct process** processes_list, struct process* process);
+void process_delete(struct process** processes_list, struct process* process);
+struct process* process_get_next(struct process* process);
+void process_exit(void);
+
+void process_display_list(struct process* processes_list);
+
+
+void process_create_user_raw(char* file, int size, char* name);
+
+#endif

include/sched/scheduler.h

@@ -7,7 +7,7 @@
 #ifndef SCHEDULER_H
 #define SCHEDULER_H
 
-struct cpu_status_t* scheduler_schedule(struct cpu_status_t* context);
+struct cpu_status* scheduler_schedule(struct cpu_status* context);
 void scheduler_init(void);
 
 #endif

include/sched/spinlock.h

@@ -0,0 +1,22 @@
+        /*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Spinlock implementation
+ * @license GPL-3.0-only
+ */
+
+#ifndef SPINLOCK_H
+#define SPINLOCK_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+struct spinlock
+{
+    bool locked;
+    uint64_t rflags;
+};
+
+void spinlock_acquire(struct spinlock* lock);
+void spinlock_release(struct spinlock* lock);
+
+#endif

include/security/ubsan.h

@@ -0,0 +1,65 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Undefined behavior sanitization hooks
+ * @license GPL-3.0-only
+ */
+
+#ifndef UBSAN_H
+#define UBSAN_H
+
+#include <stdint.h>
+
+struct ubsan_source_location
+{
+	const char* filename;
+	uint32_t line;
+	uint32_t column;
+};
+
+struct ubsan_type_descriptor
+{
+	uint16_t type_kind;
+	uint16_t type_info;
+	char type_name[];
+};
+
+struct ubsan_type_mismatch_v1_data
+{
+	struct ubsan_source_location location;
+	struct ubsan_type_descriptor* type;
+	unsigned char log_alignment;
+	unsigned char type_check_kind;
+};
+
+struct ubsan_pointer_overflow_data
+{
+	struct ubsan_source_location location;
+};
+
+struct ubsan_shift_out_of_bounds_data
+{
+	struct ubsan_source_location location;
+	struct ubsan_type_descriptor* lhs_type;
+	struct ubsan_type_descriptor* rhs_type;
+};
+
+struct ubsan_invalid_value_data
+{
+	struct ubsan_source_location location;
+	struct ubsan_type_descriptor* type;
+};
+
+struct ubsan_out_of_bounds_data
+{
+	struct ubsan_source_location location;
+	struct ubsan_type_descriptor* array_type;
+	struct ubsan_type_descriptor* index_type;
+};
+
+struct ubsan_overflow_data
+{
+	struct ubsan_source_location location;
+	struct ubsan_type_descriptor* type;
+};
+
+#endif

include/string/string.h

@@ -7,8 +7,12 @@
 #ifndef STRING_H
 #define STRING_H
 
+#include <stddef.h>
+
 char *strcpy(char *dest, const char *src);
 char *strcat(char *dest, const char *src);
 void strncpy(char* dst, const char* src, size_t n);
+int strncmp(const char* s1, const char* s2, size_t n);
+size_t strlen(const char* str);
 
 #endif

include/time/date.h

@@ -0,0 +1,25 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Date helper functions
+ * @license GPL-3.0-only
+ */
+
+#ifndef DATE_H
+#define DATE_H
+
+#include <stdint.h>
+
+struct date {
+    uint64_t year;
+    uint8_t month;
+    uint8_t day;
+
+    uint8_t hour;
+    uint8_t minute;
+    uint8_t second;
+};
+
+struct date date_timestamp_to_date(uint64_t timestamp);
+struct date date_now();
+
+#endif

limine.conf

@@ -1,6 +1,9 @@
 timeout: 3
+interface_branding: Welcome to the PepperOS disk!
 
 /PepperOS
 	protocol: limine
 	
+	comment: Default configuration (warning: spicy)
 	path: boot():/boot/pepperk
+	module_path: boot():/boot/initfs.tar

src/arch/x86/cpuid.c

@@ -0,0 +1,48 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   x86 CPU identification
+ * @license GPL-3.0-only
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+#include <kernel.h>
+#include <string/string.h>
+
+/*
+ * cpuid - Wrapper for CPUID instruction
+ * @leaf: Requested leaf (input EAX)
+ * @eax: EAX register value (output)
+ * @ebx: EBX register value (output)
+ * @ecx: ECX register value (output)
+ * @edx: EDX register value (output)
+*/
+void cpuid(uint32_t leaf, uint32_t* eax, uint32_t* ebx, uint32_t* ecx, uint32_t* edx)
+{
+    __asm__ volatile("cpuid" : "=a"(*eax), "=b"(*ebx), "=c"(*ecx), "=d"(*edx) : "a"(leaf));
+}
+
+/*
+ * cpuid_get_vendor_string - Get the CPU vendor string
+ * @str: String at least 13 bytes long (for output)
+ *
+ * Return:
+ * %0 - on success
+ */
+int cpuid_get_vendor_string(char* str)
+{
+    uint32_t eax, ebx, ecx, edx;
+    
+    cpuid(0, &eax, &ebx, &ecx, &edx);
+    char output[13] = {0};
+
+    uint32_t regs[3] = {ebx, edx, ecx};
+    for (unsigned int j=0; j<3; j++) {
+        for (unsigned int i=0; i<4; i++) {
+            output[4*j+i] = (char)((regs[j] >> 8*i) & 0xff);
+        }   
+    }
+
+    strncpy(str, output, 13);
+    return 0;
+}

src/arch/x86/gdt.c

@@ -0,0 +1,138 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Global Descriptor Table and Task State Segment setup
+ * @license GPL-3.0-only
+ */
+
+#include <arch/gdt.h>
+#include <stdint.h>
+#include <io/serial/serial.h>
+#include <kernel.h>
+
+// Descriptors are 8-byte wide (64bits)
+// So the selectors will be (in bytes): 0x0, 0x8, 0x10, 0x18, etc..
+uint64_t gdt_entries[NUM_GDT_ENTRIES];
+struct GDTR gdtr;
+
+struct tss tss = {0};
+
+/*
+ * gdt_load - Loads Global Descriptor Table
+ */
+static void gdt_load()
+{
+    asm("lgdt %0" : : "m"(gdtr));
+}
+
+/*
+ * gdt_flush - Flushes the Global Descriptor Table
+ *
+ * This function loads new Segment Selectors to make
+ * the GDT changes take effect
+ */
+static void gdt_flush()
+{
+    // Here, 0x8 is the kernel code selector
+    // and 0x10 is the kernel data selector
+    asm volatile (
+        "mov $0x10, %%ax \n" // Reload segments with kernel data selector
+        "mov %%ax, %%ds \n"
+        "mov %%ax, %%es \n"
+        "mov %%ax, %%fs \n"
+        "mov %%ax, %%gs \n"
+        "mov %%ax, %%ss \n"
+
+        "pushq $0x8      \n"   // CS reload
+        "lea 1f(%%rip), %%rax \n"
+        "push %%rax     \n"
+        "lretq          \n"
+        "1:             \n" // Execution continues here after CS reload
+        :
+        :
+        : "rax", "memory"
+    );
+}
+
+/*
+ * get_set_entry - Sets a GDT entry
+ * @num:    Number of the entry (index in GDT)
+ * @flags:  Flags (Granularity, Size, Long mode)
+ * @access: Access byte (contains Descriptor Privilege Level)
+ *
+ * This function fills a GDT entry with the specified @flags
+ * and @access byte. The base and limit fields are left to zero
+ * because we don't use segmentation for memory management.
+ */
+
+static void gdt_set_entry(int num, uint8_t flags, uint8_t access)
+{
+    uint64_t gdt_entry = 0;
+
+    gdt_entry |= (access << 8);
+    gdt_entry |= (flags << 20);
+    
+    // Rest (base, limit) is always zero
+    gdt_entries[num] = gdt_entry << 32;
+}
+
+/*
+ * gdt_set_tss - Setup the TSS entry in the GDT
+ * @num: Number of the entry (index in GDT)
+ *
+ * This function sets up a Task State Segment entry
+ * in the Global Descriptor Table.
+ *
+ * The entry is 128-bit long, so it actually takes
+ * two 64-bit GDT entries.
+ */
+static void gdt_set_tss(int num)
+{
+    uint64_t tss_base = (uint64_t)&tss;
+    uint64_t tss_limit = sizeof(struct tss) - 1;
+
+    tss.iopb = sizeof(struct tss);
+
+    uint64_t tss_low = 0;
+    tss_low |= (tss_limit & 0xFFFFULL);
+    tss_low |= (tss_base & 0xFFFFFFULL) << 16;
+    tss_low |= 0x89ULL << 40;
+    tss_low |= ((tss_limit >> 16) & 0xFULL) << 48;
+    tss_low |= ((tss_base >> 24) & 0xFFULL) << 56;
+
+    uint64_t tss_high = (tss_base >> 32) & 0xFFFFFFFFULL;
+
+    gdt_entries[num] = tss_low;
+    gdt_entries[num + 1] = tss_high;
+}
+
+/*
+ * gdt_init - Global Descriptor Table initialization 
+ *
+ * This function loads a new GDT in the CPU.
+ * It contains a null descriptor, kernel code and data
+ * segments, and user code and data segments.
+ * However, we do not use segmentation to manage memory on
+ * 64-bit x86, as it's deprecated. Instead, we use paging. 
+ */
+void gdt_init()
+{
+    gdt_set_entry(0, 0, 0); // Null descriptor  (0x0)
+    gdt_set_entry(1, 0xA, 0x9B); // Kernel code (0x8)
+    gdt_set_entry(2, 0xC, 0x93); // Kernel data (0x10)
+    gdt_set_entry(3, 0xA, 0xFB); // User code   (0x18)
+    gdt_set_entry(4, 0xC, 0xF3); // User data   (0x20)
+    gdt_set_tss(5);                            // TSS         (0x28)
+
+    // The -1 subtraction is some wizardry explained in the OSDev wiki -> GDT
+    gdtr.limit = NUM_GDT_ENTRIES * sizeof(uint64_t) - 1;
+    gdtr.address = (uint64_t)gdt_entries;
+
+    // Load the GDT we created, flush the old one
+    gdt_load();
+    gdt_flush();
+
+    // Load task register with new TSS
+    asm volatile("ltr %%ax" : : "a"(TSS_SEGMENT) : "memory");
+
+    DEBUG("GDT initialized");
+}

src/arch/x86/idt.S

@@ -32,6 +32,8 @@ global vector_19_handler
 global vector_20_handler
 global vector_21_handler
 
+global vector_128_handler
+
 interrupt_stub:
     ; We'll push all general-purpose registers to the stack,
     ; so they're intact and don't bother the code that was
@@ -313,3 +315,10 @@ vector_33_handler:
     push qword 0
     push qword 33
     jmp interrupt_stub
+
+; Syscall Interrupt (0x80)
+align 16
+vector_128_handler:
+    push qword 0
+    push qword 128
+    jmp interrupt_stub

src/arch/x86/idt.c

@@ -4,16 +4,16 @@
  * @license GPL-3.0-only
  */
 
-#include "idt.h"
+#include <arch/x86.h>
 #include <stdint.h>
 #include <stddef.h>
-#include "io/serial/serial.h"
+#include <io/serial/serial.h>
-#include "io/kbd/ps2.h"
+#include <io/kbd/ps2.h>
 #include <kernel.h>
 #include <stdbool.h>
-#include "sched/scheduler.h"
+#include <sched/scheduler.h>
-#include "config.h"
+#include <config.h>
-#include "sched/process.h"
+#include <sched/process.h>
 
 struct interrupt_descriptor idt[256];
 struct idtr idt_reg;
@@ -21,9 +21,13 @@ struct idtr idt_reg;
 // Address to our first interrupt handler
 extern char vector_0_handler[];
 
+extern char vector_128_handler[];
+
 // Timer ticks
 extern volatile uint64_t ticks;
 
+extern struct init_status init;
+
 /*
  * idt_set_entry - Sets an Interrupt Descriptor Table entry
  * @vector:  Vector number in the IDT
@@ -72,6 +76,9 @@ void idt_init()
         // Each vector handler is 16-byte aligned, so <vector_no>*16 = address of that handler
         idt_set_entry(i, vector_0_handler + (i*16), 0);
     }
+
+    idt_set_entry(0x80, vector_128_handler, 3);
+
     idt_load(&idt);
     DEBUG("IDT initialized");
 }
@@ -101,7 +108,7 @@ static inline uint64_t read_cr2(void)
  * Also displays an interpretation of the thrown error code.
  * Then halts the system. We could implement demand paging later.
  */
-static void page_fault_handler(struct cpu_status_t* ctx)
+static void page_fault_handler(struct cpu_status* ctx)
 {
     // It could be used to remap pages etc. to fix the fault, but right now what I'm more
     // interested in is getting more info out of those numbers cause i'm lost each time i have 
@@ -119,6 +126,19 @@ static void page_fault_handler(struct cpu_status_t* ctx)
     CHECK_BIT(ctx->error_code, 7) ? " SGX_VIOLATION" : "",
     cr2);
 
+    if (init.all) {
+        printf("\x1b[38;5;231mPage Fault at rip=0x%p, err=%u (%s%s%s%s%s%s%s%s) when accessing addr=0x%p\x1b[0m", ctx->iret_rip, ctx->error_code,
+        CHECK_BIT(ctx->error_code, 0) ? "PAGE_PROTECTION_VIOLATION " : "PAGE_NOT_PRESENT ",
+        CHECK_BIT(ctx->error_code, 1) ? "ON_WRITE " : "ON_READ ",
+        CHECK_BIT(ctx->error_code, 2) ? "IN_USER_MODE" : "IN_KERNEL_MODE",
+        CHECK_BIT(ctx->error_code, 3) ? " WAS_RESERVED" : "",
+        CHECK_BIT(ctx->error_code, 4) ? " ON_INSTRUCTION_FETCH" : "",
+        CHECK_BIT(ctx->error_code, 5) ? " PK_VIOLATION" : "",
+        CHECK_BIT(ctx->error_code, 6) ? " ON_SHADOWSTACK_ACCESS" : "",
+        CHECK_BIT(ctx->error_code, 7) ? " SGX_VIOLATION" : "",
+        cr2);
+    }
+
     panic(ctx, "page fault");
 }
 
@@ -129,7 +149,7 @@ static void page_fault_handler(struct cpu_status_t* ctx)
  * Shows detail about a General Protection Fault,
  * and what may have caused it. Halts the system.
  */
-static void gp_fault_handler(struct cpu_status_t* ctx)
+static void gp_fault_handler(struct cpu_status* ctx)
 {
     DEBUG("\x1b[38;5;231mGeneral Protection Fault at rip=0x%p, err=%u (%s)\x1b[0m",
     ctx->iret_rip,
@@ -165,7 +185,7 @@ static void gp_fault_handler(struct cpu_status_t* ctx)
  * Return:
  * <context> - CPU context after interrupt
  */
-struct cpu_status_t* interrupt_dispatch(struct cpu_status_t* context)
+struct cpu_status* interrupt_dispatch(struct cpu_status* context)
 {
     if (context == NULL) {
         panic(NULL, "Interrupt dispatch recieved NULL context!");
@@ -252,9 +272,14 @@ struct cpu_status_t* interrupt_dispatch(struct cpu_status_t* context)
 
         case 33: // Keyboard Interrupt
             keyboard_handler();
+            //process_create("keyboard-initiated", kbdproc_main, NULL); // DEBUG
             outb(0x20, 0x20);
             break;
         
+        case 128: // Syscall Interrupt (0x80)
+            syscall_handler(context);
+            break;
+
         default:
             DEBUG("Unexpected Interrupt");
             break;

src/arch/x86/init.c

@@ -0,0 +1,114 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   x86 architecture-dependant initialization
+ * @license GPL-3.0-only
+ */
+
+#include <arch/gdt.h>
+#include <stdint.h>
+#include <arch/x86.h>
+#include <kernel.h>
+#include <mem/utils.h>
+
+/*
+ * x86_overwrite_pat - Set PAT to WC
+ *
+ * This function overwrites the 1st Page Attribute
+ * Table entry, to enable the Write-Combining property
+ * when we map memory regions later on.
+ * The framebuffer will be mapped with WC, which makes
+ * memory access significantly faster by using burst
+ * operations. 
+*/
+
+static void x86_overwrite_pat()
+{
+    uint64_t pat = rdmsr(0x277);
+    pat &= ~(0xFFULL << 8); // Clear PAT1
+    pat |= (0x01ULL << 8); // PAT1 = 0x01 (WC)
+    wrmsr(0x277, pat);
+}
+
+/*
+ * x86_enable_fpu - Enable Floating Point Unit
+ *
+ * This function enables the Floating Point Unit,
+ * which allows the CPU to do floating point
+ * operations.
+ *
+ * Here we do not check for FPU support but we
+ * should. However most processors support it.
+ */
+static void x86_enable_fpu()
+{
+    size_t cr4;
+	__asm__ volatile("mov %%cr4, %0" : "=r"(cr4));
+	cr4 |= 0x200;
+	__asm__ volatile("mov %0, %%cr4" :: "r"(cr4));
+    uint16_t cw = 0x37F; // control word
+    asm volatile("fldcw %0" :: "m"(cw));
+}
+
+/*
+ * x86_arch_init - Initialize x86 CPU structures
+ *
+ * This function is responsible for overriding a PAT entry
+ * (to put the framebuffer area in WC mode) only.
+ *
+ * Later, all architecture-dependant init (GDT, IDT, TSS, ...)
+ * should be initialized here, and separate function pointers
+ * should be set up for each arch.
+ */
+void x86_arch_init()
+{
+    x86_overwrite_pat();
+    x86_enable_fpu();
+    x86_cpu_identification();
+    idt_init();
+    gdt_init();
+}
+
+/*
+ * cpu_supports_brandstring - Does the CPU support brand strings?
+ *
+ * Return:
+ * true  - if it does
+ * false - if it doesn't
+*/
+bool cpu_supports_brandstring() {
+    uint32_t eax, ebx, ecx, edx;
+    cpuid(0x80000000, &eax, &ebx, &ecx, &edx);
+
+    if (eax < 0x80000004) {
+        return false;
+    } else {
+        return true;
+    }
+}
+
+/*
+ * x86_cpu_idenfitication - get info about the CPU
+ *
+ * This function displays the CPU vendor name or the
+ * extended "brand string" if it's supported, on
+ * debug output.
+*/
+void x86_cpu_identification()
+{
+    if (cpu_supports_brandstring()) {
+        uint32_t regs[12];
+        // Some CPUs don't return null-terminated values so we do it as a failsafe default
+        char str[sizeof(regs)+1] = {0};
+        cpuid(0x80000002, &regs[0], &regs[1], &regs[2], &regs[3]);
+        cpuid(0x80000003, &regs[4], &regs[5], &regs[6], &regs[7]);
+        cpuid(0x80000004, &regs[8], &regs[9], &regs[10], &regs[11]);
+
+        memcpy(str, regs, sizeof(regs));
+        str[sizeof(regs)] = '\0';
+        DEBUG("CPU: %s", str);
+    } else {
+        char vendor_string[13] = {0};
+        cpuid_get_vendor_string(vendor_string);
+        DEBUG("CPU vendor is: %s", vendor_string);
+    }
+}

src/arch/x86/msr.c

@@ -0,0 +1,66 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   x86 MSR C wrappers
+ * @description
+ * Wrapper functions to access Model Specific Registers
+ *
+ * @license GPL-3.0-only
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <arch/x86.h>
+
+/*
+ * rdmsr - Read from MSR
+ * @msr: model specific register number 
+ *
+ * Read a 64-bit word from a Model Specific Register.
+ * Wrapper for the "rdmsr" instruction. It originally
+ * outputs to two 32-bit registers (EDX:EAX), so the
+ * function does the job of uniting them as a 64-bit
+ * value for us.
+ *
+ * Return:
+ * <value> - value read from MSR
+ */
+uint64_t rdmsr(uint32_t msr)
+{
+    uint32_t low;
+    uint32_t high;
+
+    __asm__ volatile("rdmsr" : "=a"(low), "=d"(high) : "c"(msr));
+
+    return ((uint64_t)high << 32) | low;
+}
+
+/*
+ * wrmsr - Write to MSR
+ * @msr: model specific register number 
+ *
+ * Write a 64-bit value to a Model Specific Register.
+ */
+void wrmsr(uint32_t msr, uint64_t value)
+{
+    uint32_t low = (uint32_t)(value & 0xFFFFFFFF);
+    uint32_t high = (uint32_t)(value >> 32);
+
+    __asm__ volatile("wrmsr" : : "c"(msr), "a"(low), "d"(high) : "memory");
+}
+
+/*
+ * x86_has_msr - Test for MSR support
+ *
+ * Checks if CPU supports Model Specific Registers
+ * using CPUID.01h:EDX[bit 5].
+ *
+ * Return:
+ * true  - MSR are supported
+ * false - MSR are not supported 
+ */
+bool x86_has_msr()
+{
+    uint32_t eax, ebx, ecx, edx;
+    cpuid(1, &eax, &ebx, &ecx, &edx);
+    return (edx & (1 << 5)) != 0;
+}

src/arch/x86/syscall.c

@@ -0,0 +1,160 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   System call handling
+ * @license GPL-3.0-only
+ */
+
+#include "config.h"
+#include "sched/scheduler.h"
+#include <arch/x86.h>
+#include <kernel.h>
+#include <stddef.h>
+#include <io/term/term.h>
+#include <sched/process.h>
+#include <io/kbd/ps2.h>
+#include <fs/initfs.h>
+#include <string/string.h>
+
+extern struct process* current_process;
+
+// Return fd on success, -errno on error
+int sys_open(const char* filename, int flags)
+{
+    if (tar_exists(filename) < 0) {
+        return -ENOENT; // file doesn't exist..
+    }
+    // file exists here!
+    if (current_process->next_free_fd >= FDT_MAX) {
+        return -EMFILE;
+    }
+    int fd = current_process->next_free_fd++;
+    current_process->fdt[fd].fd = fd;
+    current_process->fdt[fd].open = true;
+    current_process->fdt[fd].cursor = 0;
+    strncpy(current_process->fdt[fd].filename, filename, PROCESS_NAME_MAX - 1);
+    return fd;
+}
+
+// Return 0 on success, -EBADFD if invalid FD
+int sys_close(int fd)
+{
+    if (fd < 0 || fd >= FDT_MAX) {
+        return -EBADFD;
+    }
+
+    if (!current_process->fdt[fd].open) {
+        return -EBADFD; // FD not opened in the first place
+    }
+
+    current_process->fdt[fd].open = false;
+    current_process->fdt[fd].filename[0] = '\0';
+    current_process->fdt[fd].cursor = 0;
+    return 0;
+}
+
+// Should return the number of bytes read
+int sys_read(unsigned int fd, char* buf, size_t count)
+{
+    size_t i;
+    switch (fd) {
+        case 0: //read from stdin (keyboard)
+            for (i=0; i<count; i++) {
+                buf[i] = keyboard_getchar();
+            }
+            return i;
+        case 1: // from stdout
+        case 2: // from stderr
+            return -EBADFD;
+        default: // from an open file?
+            if (current_process->fdt[fd].open == false) {
+                return -EBADFD; // File descriptor wasn't open
+            }
+            // Here fd refers to a valid opened file..
+            int sz = tar_read(current_process->fdt[fd].filename, buf, count,
+                            current_process->fdt[fd].cursor);
+            if (sz == 0) {
+                return -ENOENT;
+            } else {
+                current_process->fdt[fd].cursor += sz;
+                return sz;
+            }
+    }
+
+    return -EBADFD;
+}
+
+// TODO: Should have a return value: number of bytes written on success, -1 on error (errno set) 
+int sys_write(unsigned int fd, const char* buf, size_t count)
+{
+    switch (fd) {
+        case 1: //stdout
+        case 2: //stderr
+            for (size_t i=0; i<count; i++) {
+                internal_putc(buf[i], NULL);
+            }
+            return count;
+        default:
+            return -EBADFD;
+    }
+}
+
+int sys_exit(int error_code)
+{
+    current_process->status = DEAD;
+    DEBUG("(pid=%u, name=%s)", current_process->pid, current_process->name);
+    return error_code;
+}
+
+/*
+ * syscall_handler - System call dispatcher
+ * @regs: CPU state
+ *
+ * This function is called from the interrupt dispatcher,
+ * when an interrupt 0x80 is emitted from userland.
+ *
+ * It switches control to the syscall number provided
+ * in %rax. 
+ *
+ * We try to follow the System V convention here:
+ * - syscall number in %rax
+ * - args in %rdi, %rsi, %rdx, %r10, %r8, %r9
+ * - return value (if any) in %rax
+ *
+ * Return:
+ * <regs> - CPU state after system call
+ */
+struct cpu_status* syscall_handler(struct cpu_status* regs)
+{
+    switch (regs->rax)
+    {
+        case 0:
+            DEBUG("sys_read(fd=%u, buf=%p, count=%u)", regs->rdi, regs->rsi, regs->rdx);
+            regs->rax = sys_read(regs->rdi, (char*)regs->rsi, regs->rdx);
+            break;
+        case 1:
+            DEBUG("sys_write(fd=%u, buf=%p, count=%u)", regs->rdi, regs->rsi, regs->rdx);
+            regs->rax = sys_write(regs->rdi, (char*)regs->rsi, regs->rdx);
+            break;
+        case 2:
+            DEBUG("sys_open(filename=%s, flags=%u)", regs->rdi, regs->rsi);
+            regs->rax = sys_open((const char*)regs->rdi, regs->rsi);
+            break;
+        case 3:
+            DEBUG("sys_close(fd=%u)", regs->rdi);
+            regs->rax = sys_close(regs->rdi);
+            break;
+        case 60:
+            DEBUG("sys_exit(error_code=%d)", regs->rdi);
+            regs->rax = sys_exit(regs->rdi);
+            break;
+        default:
+            DEBUG("Bad syscall! (rax=%p, rdi=%p, rsi=%p, rdx=%p)",
+                    regs->rax, regs->rdi, regs->rsi, regs->rdx);
+            regs->rax = 0xbad515ca11;
+            break;
+    }
+
+    DEBUG("returned rax=%p (%u)", regs->rax, regs->rax);
+
+    return regs;
+}

src/boot/boot.c

@@ -9,7 +9,12 @@
  * @license GPL-3.0-only
  */
 
+#include <kernel.h>
 #include <limine.h>
+#include <stddef.h>
+
+__attribute__((used, section(".limine_requests_start")))
+volatile LIMINE_REQUESTS_START_MARKER;
 
 __attribute__((used, section(".limine_requests")))
 volatile struct limine_framebuffer_request framebuffer_request = {
@@ -35,8 +40,29 @@ volatile struct limine_kernel_address_request kerneladdr_request = {
 	.revision = 0
 };
 
-__attribute__((used, section(".limine_requests_start")))
+__attribute__((used, section(".limine_requests")))
-volatile LIMINE_REQUESTS_START_MARKER;
+volatile struct limine_boot_time_request date_request = {
+	.id = LIMINE_BOOT_TIME_REQUEST,
+	.revision = 0
+};
+
+__attribute__((used, section(".limine_requests")))
+volatile struct limine_module_request module_request = {
+	.id = LIMINE_MODULE_REQUEST,
+	.revision = 0
+};
 
 __attribute__((used, section(".limine_requests_end")))
 volatile LIMINE_REQUESTS_END_MARKER;
+
+void populate_boot_context(struct boot_context* ctx)
+{
+	// Populate boot context
+	// This stays valid only if the BOOTLOADER_RECLAIMABLE regions are preserved
+ 	ctx->fb = framebuffer_request.response ? framebuffer_request.response->framebuffers[0] : NULL;
+	ctx->mmap = memmap_request.response ? memmap_request.response : NULL;
+	ctx->hhdm = hhdm_request.response ? hhdm_request.response : NULL;
+	ctx->kaddr = kerneladdr_request.response ? kerneladdr_request.response : NULL;
+	ctx->bootdate = date_request.response ? date_request.response : NULL;
+	ctx->module = module_request.response ? module_request.response : NULL;
+}

src/config.h

@@ -1,45 +0,0 @@
-/*
- * @author  xamidev <xamidev@riseup.net>
- * @brief   PepperOS configuration file
- * @license GPL-3.0-only
- */
-
-#ifndef CONFIG_H
-#define CONFIG_H
-
-/* version */
-#define PEPPEROS_VERSION_MAJOR "0"
-#define PEPPEROS_VERSION_MINOR "0"
-#define PEPPEROS_VERSION_PATCH "58"
-#define PEPPEROS_SPLASH "\x1b[38;5;196mPepperOS\x1b[0m version "PEPPEROS_VERSION_MAJOR"."PEPPEROS_VERSION_MINOR"."PEPPEROS_VERSION_PATCH"\n"
-
-/* process */
-#define PROCESS_NAME_MAX 64
-#define PROCESS_STACK_SIZE 0x10000 // 64kb
-#define PROCESS_BASE 0x400000
-#define PROCESS_STACK_BASE 0x1000000
-
-/* sched */
-// 1 tick = 1 ms => quantum = 10ms
-#define SCHEDULER_QUANTUM 10
-
-/* kernel */
-#define KERNEL_BASE 0xFFFFFFFF80000000ULL
-// 2 MB should be enough (as of now, the whole kernel ELF is around 75kb)
-#define KERNEL_SIZE 0x200000
-#define KERNEL_STACK_SIZE 65536
-#define KERNEL_IDT_ENTRIES 33
-
-/* paging */
-#define PAGING_MAX_PHYS 0x100000000
-
-/* heap */
-#define KHEAP_SIZE (32*1024*1024)
-
-/* term */
-#define TERM_HISTORY_MAX_LINES 256
-
-/* time */
-#define TIMER_FREQUENCY 1000
-
-#endif

src/debug/misc.c

@@ -5,8 +5,9 @@
  */
 
 #include <kernel.h>
-#include "limine.h"
+#include <limine.h>
-#include "string/string.h"
+#include <string/string.h>
+#include <stddef.h>
 
 extern struct boot_context boot_ctx;
 

src/debug/panic.c

@@ -5,11 +5,38 @@
  */
 
 #include <stddef.h>
-#include "idt/idt.h"
+#include <arch/x86.h>
-#include "io/serial/serial.h"
+#include <io/serial/serial.h>
-#include "kernel.h"
+#include <kernel.h>
 
 extern struct init_status init;
+extern int panic_count;
+
+/*
+ * reaf_rflags - provide easy reading of the RFLAGS register
+ * @rflags: RFLAGS register value
+ */
+void read_rflags(uint64_t rflags)
+{
+	printf("\x1b[38;5;226m%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s\x1b[38;5;231m",
+		CHECK_BIT(rflags, 0) ? "CF " : "", /*carry flag*/
+		CHECK_BIT(rflags, 2) ? "PF " : "", /*parity flag*/
+		CHECK_BIT(rflags, 4) ? "AF " : "", /*auxiliary carry flag*/
+		CHECK_BIT(rflags, 6) ? "ZF " : "", /*zero flag*/
+		CHECK_BIT(rflags, 7) ? "SF " : "", /*sign flag*/
+		CHECK_BIT(rflags, 8) ? "TF " : "", /*trap flag*/
+		CHECK_BIT(rflags, 9) ? "IF " : "", /*interrupt enable flag*/
+		CHECK_BIT(rflags, 10) ? "DF " : "", /*direction flag*/
+		CHECK_BIT(rflags, 11) ? "OF " : "", /*overflow flag*/
+		(CHECK_BIT(rflags, 12) && CHECK_BIT(rflags, 13)) ? "IOPL3 " : "IOPL0 ", /*io privilege lvl*/
+		CHECK_BIT(rflags, 14) ? "NT " : "", /*nested task*/
+		CHECK_BIT(rflags, 16) ? "RF " : "", /*resume flag*/
+		CHECK_BIT(rflags, 17) ? "VM " : "", /*virtual 8086 mode*/
+		CHECK_BIT(rflags, 18) ? "AC " : "", /*alignment check/access control*/
+		CHECK_BIT(rflags, 19) ? "VIF " : "", /*virtual interrupt flag*/
+		CHECK_BIT(rflags, 20) ? "VIP " : "", /*virtual interrupt pending*/
+		CHECK_BIT(rflags, 21) ? "ID " : ""); /*id flag*/
+}
 
 /*
  * panic - Kernel panic
@@ -20,39 +47,24 @@ extern struct init_status init;
  * Will display to terminal if it is initialized, otherwise serial only.
  * Can be called with or without a CPU context.
  */
-void panic(struct cpu_status_t* ctx, const char* str)
+void panic(struct cpu_status* ctx, const char* str)
 {
 	CLEAR_INTERRUPTS;
+	panic_count += 1;
 	if (ctx == NULL) {
-		DEBUG("\x1b[38;5;231m\x1b[48;5;196mKernel panic!!!\x1b[0m Something went horribly wrong! (no cpu ctx)");
-		fctprintf((void*)&skputc, 0, "\x1b[38;5;231m\x1b[48;5;27m");
-		DIE_DEBUG(str);
-		fctprintf((void*)&skputc, 0, "\x1b[0m");
-		skputc('\r');
-		skputc('\n');
-		DEBUG("\x1b[38;5;231m\x1b[48;5;196mend Kernel panic - halting...\x1b[0m");
-
-		if (init.terminal) {
 		printf("\r\n\x1b[38;5;231m\x1b[48;5;196mKernel panic!!!\x1b[48;5;232m Something went horribly wrong! (no cpu ctx)");
-			printf("\r\n%s\r\n\x1b[38;5;231mend Kernel panic - halting...\x1b[0m", str);
+		printf("\r\n%s\r\n\x1b[38;5;231m\x1b[0m", str);
-		}
+		debug_stack_trace(100);
-
 		hcf();
 	}
-	DEBUG("\x1b[38;5;231m\x1b[48;5;196mKernel panic!!!\x1b[0m at rip=%p\r\nSomething went horribly wrong! (%s) vect=0x%.2x errcode=0x%x\n\rrax=%p rbx=%p rcx=%p rdx=%p\n\rrsi=%p rdi=%p  r8=%p  r9=%p\n\rr10=%p r11=%p r12=%p r13=%p\n\rr14=%p r15=%p\n\n\rflags=%p\n\rHalting...\x1b[0m",
+
+	printf("\r\n\x1b[38;5;231m\x1b[48;5;196mKernel panic!!!\x1b[48;5;232mat rip=%p\r\nSomething went horribly wrong! (%s) vect=0x%.2x errcode=0x%x\n\rrax=%p rbx=%p rcx=%p rdx=%p\n\rrsi=%p rdi=%p  r8=%p  r9=%p\n\rr10=%p r11=%p r12=%p r13=%p\n\rr14=%p r15=%p\n\n\rflags=%p ",
 	ctx->iret_rip,
 	str,
 	ctx->vector_number, ctx->error_code, ctx->rax, ctx->rbx, ctx->rcx, ctx->rdx, ctx->rsi, ctx->rdi,
 	ctx->r8, ctx->r9, ctx->r10, ctx->r11, ctx->r12, ctx->r13, ctx->r14, ctx->r15, ctx->iret_flags);
 
-	if (init.terminal) {
+	read_rflags(ctx->iret_flags);
-		printf("\r\n\x1b[38;5;231m\x1b[48;5;196mKernel panic!!!\x1b[48;5;232mat rip=%p\r\nSomething went horribly wrong! (%s) vect=0x%.2x errcode=0x%x\n\rrax=%p rbx=%p rcx=%p rdx=%p\n\rrsi=%p rdi=%p  r8=%p  r9=%p\n\rr10=%p r11=%p r12=%p r13=%p\n\rr14=%p r15=%p\n\n\rflags=%p\n\rHalting...\x1b[0m",
-		ctx->iret_rip,
-		str,
-		ctx->vector_number, ctx->error_code, ctx->rax, ctx->rbx, ctx->rcx, ctx->rdx, ctx->rsi, ctx->rdi,
-		ctx->r8, ctx->r9, ctx->r10, ctx->r11, ctx->r12, ctx->r13, ctx->r14, ctx->r15, ctx->iret_flags);
-	}
-	
 	debug_stack_trace(100);
 	
 	hcf();

src/debug/stacktrace.c

@@ -5,7 +5,8 @@
  */
 
 #include <stdint.h>
-#include "kernel.h"
+#include <kernel.h>
+#include <stddef.h>
 
 extern struct init_status init;
 
@@ -18,10 +19,8 @@ extern struct init_status init;
  */
 void debug_stack_trace(unsigned int max_frames)
 {
-    DEBUG("*** begin stack trace ***");
-    if (init.terminal) {
     printf("\r\n\x1b[48;5;232m\x1b[38;5;231m*** begin stack trace ***\r\n");
-    }
+
     // Thanks GCC :)
     uintptr_t* rbp = (uintptr_t*)__builtin_frame_address(0);
 
@@ -30,11 +29,7 @@ void debug_stack_trace(unsigned int max_frames)
         uintptr_t rip = rbp[1];
         uintptr_t offset = 0;
         const char* name = debug_find_symbol(rip, &offset);
-        DEBUG("[%u] <0x%p> (%s+0x%x)", frame, (void*)rip, name, offset);
-
-        if (init.terminal) {
         printf("[%u] <0x%p> (%s+0x%x)\r\n", frame, (void*)rip, name, offset);
-        }
 
         uintptr_t* next_rbp = (uintptr_t*)rbp[0];
 
@@ -45,10 +40,8 @@ void debug_stack_trace(unsigned int max_frames)
 
         rbp = next_rbp;
     }
-    if (init.terminal) {
+
-        printf("*** end stack trace ***\x1b[0m");
+    printf("*** end stack trace ***\r\n[end Kernel panic]\r\nHalting system...\x1b[0m");
-    }
-    DEBUG("*** end stack trace ***");
 }
 
 typedef struct {

src/fs/initfs.c

@@ -0,0 +1,147 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Initial TAR filesystem (read-only)
+ * @license GPL-3.0-only
+ */
+
+#include <sched/process.h>
+#include <limine.h>
+#include <fs/initfs.h>
+#include <kernel.h>
+#include <mem/utils.h>
+#include <string/string.h>
+
+void* archive_start_addr;
+uint64_t archive_size;
+
+/*
+ * tar_oct2bin - convert octal size string to an integer 
+ * @str:  octal size string
+ * @size: size of string
+ *
+ * Return:
+ * $n - file size as an integer
+ */
+int tar_oct2bin(unsigned char* str, int size)
+{
+    int n = 0;
+    unsigned char* c = str;
+    while (size-- > 0) {
+        n *= 8;
+        n += *c - '0';
+        c++;
+    }
+    return n;
+}
+
+/*
+ * tar_lookup - lookup a file in the TAR file
+ * @archive:  pointer to beginning of the archive
+ * @filename: file to lookup (absolute path)
+ * @out:      where to store file data if found
+ *
+ * Return:
+ * $filesize - size of the file, if found 
+ * $-ENOENT  - file not found
+ */
+int tar_lookup(unsigned char* archive, char* filename, char** out)
+{
+    unsigned char *ptr = archive;
+
+    while (!memcmp(ptr + 257, "ustar", 5)) {
+        int filesize = tar_oct2bin(ptr + 0x7c, 11);
+        if (!memcmp(ptr, filename, strlen(filename) + 1)) {
+            *out = (char*)(ptr + 512);
+            return filesize;
+        }
+        ptr += (((filesize + 511) / 512) + 1) * 512;
+    }
+    return -ENOENT;
+}
+
+/*
+ * tar_list - list all files present in archive
+ */
+void tar_list()
+{
+    printf("++ Contents of initial filesystem ++\r\n\r\n");
+    unsigned char *ptr = archive_start_addr;
+
+    while (!memcmp(ptr + 257, "ustar", 5)) {
+        int filesize = tar_oct2bin(ptr + 0x7c, 11);
+        char* filename = (char*)ptr;
+        printf("file: %s\r\n", filename);
+        ptr += (((filesize + 511) / 512) + 1) * 512;
+    }
+}
+
+/*
+ * tar_read - read a file in the TAR archive
+ * @filename: file to read (absolute path)
+ * @out:      where to store file data if found
+ * @count:    amount of bytes to read
+ * @offset:   read from byte offset (0 for none)
+ *
+ * Return:
+ * $filesize - size of the file, if found 
+ * $-ENOENT  - file not found
+ */
+int tar_read(char* filename, char* out, int count, int offset)
+{
+    char* file_data;
+    int filesize = tar_lookup(archive_start_addr, filename, &file_data);
+
+    if (filesize <= 0) {
+        return filesize;
+    }
+
+    if (offset >= filesize) {
+        return -EINVAL;
+    }
+
+    int remaining = filesize - offset;
+    int to_read = remaining < count ? remaining : count;
+
+    memcpy(out, file_data + offset, to_read);
+
+    return to_read;
+}
+
+/*
+ * tar_exists - check if a file exists in the TAR archive
+ * @filename: file to check (absolute path)
+ *
+ * Return:
+ * $filesize - size of the file, if found 
+ * $-ENOENT  - file not found
+ */
+int tar_exists(const char* filename)
+{
+    unsigned char* ptr = archive_start_addr;
+
+    while (!memcmp(ptr + 257, "ustar", 5)) {
+        int filesize = tar_oct2bin(ptr + 0x7c, 11);
+        if (!memcmp(ptr, filename, strlen(filename) + 1)) {
+            return filesize;
+        }
+        ptr += (((filesize + 511) / 512) + 1) * 512;
+    }
+    return -ENOENT;
+}
+
+
+/*
+ * initfs_init - initialize the TAR initial filesystem
+ * @tar_file: pointer to the Limine-loaded archive
+ *
+ * Return:
+ * $0       - on success
+ */
+int initfs_init(struct limine_file* tar_file)
+{
+    archive_start_addr = tar_file->address;
+    archive_size = tar_file->size;
+
+    DEBUG("Loaded TAR initial filesystem (initfs.tar)");
+    return 0;
+}

src/io/kbd/ps2.c

@@ -4,11 +4,13 @@
  * @license GPL-3.0-only
  */
 
-#include "io/serial/serial.h"
+#include "config.h"
-#include "ps2.h"
+#include <io/serial/serial.h>
+#include <io/kbd/ps2.h>
 #include <stdint.h>
-#include "io/term/term.h"
+#include <io/term/term.h>
 #include <kernel.h>
+#include <stddef.h>
 
 // The key status bitfield will be used to see if ALT, CONTROL, or SHIFT is pressed
 uint8_t key_status = 0b00000000;
@@ -17,6 +19,11 @@ uint8_t key_status = 0b00000000;
 unsigned char* keymap;
 unsigned char* keymap_shifted;
 
+// Keyboard buffer
+char keyboard_buffer[KBD_BUFFER_MAX] = {0};
+int write_index = 0;
+int read_index = 0;
+
 extern struct init_status init;
 
 unsigned char kbdus[128] =
@@ -209,10 +216,11 @@ void keyboard_handler()
 
                     if (c) {
                         if (c == '\n') {
-                            _putchar('\r');
+                            internal_putc('\r', NULL);
                         }
-                        // Should probably have a keyboard buffer here... instead of this
+
-                        _putchar(c);
+                        internal_putc(c, NULL);
+                        keyboard_putchar(c);
                     }
                 }
             }
@@ -220,6 +228,85 @@ void keyboard_handler()
     }
 }
 
+/*
+ * keyboard_getchar - Get a character from keyboard
+ *
+ * This function reads one character from the keyboard buffer.
+ * If the keyboard buffer is empty, it will block until a key
+ * is pressed.
+ *
+ * Return:
+ * <char> - character from keyboard buffer
+ */
+char keyboard_getchar()
+{
+    while (read_index == write_index); // Empty buffer
+
+    char c = keyboard_buffer[read_index];
+    read_index = (read_index+1) % KBD_BUFFER_MAX;
+    return c;
+}
+
+/*
+ * keyboard_putchar - Puts a character in the keyboard buffer
+ * @c: character to add
+ *
+ * This function is used in the keyboard handler to add new
+ * characters to the keyboard buffer.
+ *
+ * Return:
+ * %-1 - keyboard buffer is full
+ * %0 - operation completed successfully
+ */
+int keyboard_putchar(char c)
+{
+    if ((write_index+1) % KBD_BUFFER_MAX == read_index) {
+        // Full buffer
+        return -1;
+   }
+   
+   keyboard_buffer[write_index] = c;
+   write_index = (write_index+1) % KBD_BUFFER_MAX;
+   return 0;
+}
+
+/*
+ * keyboard_getline - Gets a line of input from keyboard
+ * @output: Output string
+ * @size:   Size of output string
+ *
+ * Read a line of characters from the keyboard, until the
+ * buffer fills or a newline character is read.
+ * The output string is NULL-terminated.
+ *
+ * Return:
+ * <num> - the number of characters read
+ */
+int keyboard_getline(char* output, size_t size)
+{
+    char c;
+    size_t index = 0;
+    
+    // Read until Enter is pressed
+    while ((c = keyboard_getchar()) != 0x0A) {
+        if (c == '\b') {
+            if (index > 0) {
+                index--;
+                output[index] = '\0';
+                printf(" \b");
+            }
+            continue;
+        }
+
+        if (index >= size-1) {
+            continue;
+        }
+        output[index++] = c;
+    }
+    output[index] = '\0';
+    return index;
+}
+
 /*
  * keyboard_init - Keyboard initialization
  * @layout: Desired layout

src/io/serial/serial.c

@@ -5,10 +5,14 @@
  */
  
 #include <kernel.h>
-#include "serial.h"
+#include <io/serial/serial.h>
+#include <sched/spinlock.h>
 
 extern struct init_status init;
 
+extern int panic_count;
+struct spinlock serial_lock = {0};
+
 /*
  * outb - Writes a byte to a CPU port
  * @port: CPU port to write to
@@ -61,8 +65,8 @@ int serial_init()
     // Set normal operation mode
     outb(PORT + 4, 0x0F);
 
-    DEBUG("*** Welcome to PepperOS! ***");
     init.serial = true;
+    DEBUG("*** Welcome to PepperOS! (built @ %s %s) ***", __DATE__, __TIME__);
     return 0;
 }
 
@@ -85,9 +89,15 @@ static int is_transmit_empty()
  */
 void skputc(char c)
 {
-    // TODO: Spinlock here (serial access)
+    if (panic_count == 0) {
+        spinlock_acquire(&serial_lock);
         while (!is_transmit_empty()); // wait for free spot
         outb(PORT, c);
+        spinlock_release(&serial_lock);
+    } else {
+        while (!is_transmit_empty());
+        outb(PORT, c);
+    }
 }
 
 /*

src/io/term/flanterm.c

@@ -41,7 +41,7 @@
 #define FLANTERM_IN_FLANTERM
 #endif
 
-#include "flanterm.h"
+#include <io/term/flanterm.h>
 
 // Tries to implement this standard for terminfo
 // https://man7.org/linux/man-pages/man4/console_codes.4.html

src/io/term/flanterm_backends/fb.c

@@ -51,8 +51,8 @@
 #define FLANTERM_IN_FLANTERM
 #endif
 
-#include "../flanterm.h"
+#include <io/term/flanterm.h>
-#include "fb.h"
+#include <io/term/flanterm_backends/fb.h>
 
 void *memset(void *, int, size_t);
 void *memcpy(void *, const void *, size_t);

src/io/term/printf.c

@@ -1,914 +0,0 @@
-///////////////////////////////////////////////////////////////////////////////
-// \author (c) Marco Paland (info@paland.com)
-//             2014-2019, PALANDesign Hannover, Germany
-//
-// \license The MIT License (MIT)
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in
-// all copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-// THE SOFTWARE.
-//
-// \brief Tiny printf, sprintf and (v)snprintf implementation, optimized for speed on
-//        embedded systems with a very limited resources. These routines are thread
-//        safe and reentrant!
-//        Use this instead of the bloated standard/newlib printf cause these use
-//        malloc for printf (and may not be thread safe).
-//
-///////////////////////////////////////////////////////////////////////////////
-
-#include <stdbool.h>
-#include <stdint.h>
-
-#include "printf.h"
-
-
-// define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H ...) to include the
-// printf_config.h header file
-// default: undefined
-#ifdef PRINTF_INCLUDE_CONFIG_H
-#include "printf_config.h"
-#endif
-
-
-// 'ntoa' conversion buffer size, this must be big enough to hold one converted
-// numeric number including padded zeros (dynamically created on stack)
-// default: 32 byte
-#ifndef PRINTF_NTOA_BUFFER_SIZE
-#define PRINTF_NTOA_BUFFER_SIZE    32U
-#endif
-
-// 'ftoa' conversion buffer size, this must be big enough to hold one converted
-// float number including padded zeros (dynamically created on stack)
-// default: 32 byte
-#ifndef PRINTF_FTOA_BUFFER_SIZE
-#define PRINTF_FTOA_BUFFER_SIZE    32U
-#endif
-
-// support for the floating point type (%f)
-// default: activated
-#ifndef PRINTF_DISABLE_SUPPORT_FLOAT
-#define PRINTF_SUPPORT_FLOAT
-#endif
-
-// support for exponential floating point notation (%e/%g)
-// default: activated
-#ifndef PRINTF_DISABLE_SUPPORT_EXPONENTIAL
-#define PRINTF_SUPPORT_EXPONENTIAL
-#endif
-
-// define the default floating point precision
-// default: 6 digits
-#ifndef PRINTF_DEFAULT_FLOAT_PRECISION
-#define PRINTF_DEFAULT_FLOAT_PRECISION  6U
-#endif
-
-// define the largest float suitable to print with %f
-// default: 1e9
-#ifndef PRINTF_MAX_FLOAT
-#define PRINTF_MAX_FLOAT  1e9
-#endif
-
-// support for the long long types (%llu or %p)
-// default: activated
-#ifndef PRINTF_DISABLE_SUPPORT_LONG_LONG
-#define PRINTF_SUPPORT_LONG_LONG
-#endif
-
-// support for the ptrdiff_t type (%t)
-// ptrdiff_t is normally defined in <stddef.h> as long or long long type
-// default: activated
-#ifndef PRINTF_DISABLE_SUPPORT_PTRDIFF_T
-#define PRINTF_SUPPORT_PTRDIFF_T
-#endif
-
-///////////////////////////////////////////////////////////////////////////////
-
-// internal flag definitions
-#define FLAGS_ZEROPAD   (1U <<  0U)
-#define FLAGS_LEFT      (1U <<  1U)
-#define FLAGS_PLUS      (1U <<  2U)
-#define FLAGS_SPACE     (1U <<  3U)
-#define FLAGS_HASH      (1U <<  4U)
-#define FLAGS_UPPERCASE (1U <<  5U)
-#define FLAGS_CHAR      (1U <<  6U)
-#define FLAGS_SHORT     (1U <<  7U)
-#define FLAGS_LONG      (1U <<  8U)
-#define FLAGS_LONG_LONG (1U <<  9U)
-#define FLAGS_PRECISION (1U << 10U)
-#define FLAGS_ADAPT_EXP (1U << 11U)
-
-
-// import float.h for DBL_MAX
-#if defined(PRINTF_SUPPORT_FLOAT)
-#include <float.h>
-#endif
-
-
-// output function type
-typedef void (*out_fct_type)(char character, void* buffer, size_t idx, size_t maxlen);
-
-
-// wrapper (used as buffer) for output function type
-typedef struct {
-  void  (*fct)(char character, void* arg);
-  void* arg;
-} out_fct_wrap_type;
-
-
-// internal buffer output
-static inline void _out_buffer(char character, void* buffer, size_t idx, size_t maxlen)
-{
-  if (idx < maxlen) {
-    ((char*)buffer)[idx] = character;
-  }
-}
-
-
-// internal null output
-static inline void _out_null(char character, void* buffer, size_t idx, size_t maxlen)
-{
-  (void)character; (void)buffer; (void)idx; (void)maxlen;
-}
-
-
-// internal _putchar wrapper
-static inline void _out_char(char character, void* buffer, size_t idx, size_t maxlen)
-{
-  (void)buffer; (void)idx; (void)maxlen;
-  if (character) {
-    _putchar(character);
-  }
-}
-
-
-// internal output function wrapper
-static inline void _out_fct(char character, void* buffer, size_t idx, size_t maxlen)
-{
-  (void)idx; (void)maxlen;
-  if (character) {
-    // buffer is the output fct pointer
-    ((out_fct_wrap_type*)buffer)->fct(character, ((out_fct_wrap_type*)buffer)->arg);
-  }
-}
-
-
-// internal secure strlen
-// \return The length of the string (excluding the terminating 0) limited by 'maxsize'
-static inline unsigned int _strnlen_s(const char* str, size_t maxsize)
-{
-  const char* s;
-  for (s = str; *s && maxsize--; ++s);
-  return (unsigned int)(s - str);
-}
-
-
-// internal test if char is a digit (0-9)
-// \return true if char is a digit
-static inline bool _is_digit(char ch)
-{
-  return (ch >= '0') && (ch <= '9');
-}
-
-
-// internal ASCII string to unsigned int conversion
-static unsigned int _atoi(const char** str)
-{
-  unsigned int i = 0U;
-  while (_is_digit(**str)) {
-    i = i * 10U + (unsigned int)(*((*str)++) - '0');
-  }
-  return i;
-}
-
-
-// output the specified string in reverse, taking care of any zero-padding
-static size_t _out_rev(out_fct_type out, char* buffer, size_t idx, size_t maxlen, const char* buf, size_t len, unsigned int width, unsigned int flags)
-{
-  const size_t start_idx = idx;
-
-  // pad spaces up to given width
-  if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) {
-    for (size_t i = len; i < width; i++) {
-      out(' ', buffer, idx++, maxlen);
-    }
-  }
-
-  // reverse string
-  while (len) {
-    out(buf[--len], buffer, idx++, maxlen);
-  }
-
-  // append pad spaces up to given width
-  if (flags & FLAGS_LEFT) {
-    while (idx - start_idx < width) {
-      out(' ', buffer, idx++, maxlen);
-    }
-  }
-
-  return idx;
-}
-
-
-// internal itoa format
-static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t maxlen, char* buf, size_t len, bool negative, unsigned int base, unsigned int prec, unsigned int width, unsigned int flags)
-{
-  // pad leading zeros
-  if (!(flags & FLAGS_LEFT)) {
-    if (width && (flags & FLAGS_ZEROPAD) && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
-      width--;
-    }
-    while ((len < prec) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
-      buf[len++] = '0';
-    }
-    while ((flags & FLAGS_ZEROPAD) && (len < width) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
-      buf[len++] = '0';
-    }
-  }
-
-  // handle hash
-  if (flags & FLAGS_HASH) {
-    if (!(flags & FLAGS_PRECISION) && len && ((len == prec) || (len == width))) {
-      len--;
-      if (len && (base == 16U)) {
-        len--;
-      }
-    }
-    if ((base == 16U) && !(flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
-      buf[len++] = 'x';
-    }
-    else if ((base == 16U) && (flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
-      buf[len++] = 'X';
-    }
-    else if ((base == 2U) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
-      buf[len++] = 'b';
-    }
-    if (len < PRINTF_NTOA_BUFFER_SIZE) {
-      buf[len++] = '0';
-    }
-  }
-
-  if (len < PRINTF_NTOA_BUFFER_SIZE) {
-    if (negative) {
-      buf[len++] = '-';
-    }
-    else if (flags & FLAGS_PLUS) {
-      buf[len++] = '+';  // ignore the space if the '+' exists
-    }
-    else if (flags & FLAGS_SPACE) {
-      buf[len++] = ' ';
-    }
-  }
-
-  return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags);
-}
-
-
-// internal itoa for 'long' type
-static size_t _ntoa_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long value, bool negative, unsigned long base, unsigned int prec, unsigned int width, unsigned int flags)
-{
-  char buf[PRINTF_NTOA_BUFFER_SIZE];
-  size_t len = 0U;
-
-  // no hash for 0 values
-  if (!value) {
-    flags &= ~FLAGS_HASH;
-  }
-
-  // write if precision != 0 and value is != 0
-  if (!(flags & FLAGS_PRECISION) || value) {
-    do {
-      const char digit = (char)(value % base);
-      buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
-      value /= base;
-    } while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
-  }
-
-  return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags);
-}
-
-
-// internal itoa for 'long long' type
-#if defined(PRINTF_SUPPORT_LONG_LONG)
-static size_t _ntoa_long_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long long value, bool negative, unsigned long long base, unsigned int prec, unsigned int width, unsigned int flags)
-{
-  char buf[PRINTF_NTOA_BUFFER_SIZE];
-  size_t len = 0U;
-
-  // no hash for 0 values
-  if (!value) {
-    flags &= ~FLAGS_HASH;
-  }
-
-  // write if precision != 0 and value is != 0
-  if (!(flags & FLAGS_PRECISION) || value) {
-    do {
-      const char digit = (char)(value % base);
-      buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
-      value /= base;
-    } while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
-  }
-
-  return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags);
-}
-#endif  // PRINTF_SUPPORT_LONG_LONG
-
-
-#if defined(PRINTF_SUPPORT_FLOAT)
-
-#if defined(PRINTF_SUPPORT_EXPONENTIAL)
-// forward declaration so that _ftoa can switch to exp notation for values > PRINTF_MAX_FLOAT
-static size_t _etoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags);
-#endif
-
-
-// internal ftoa for fixed decimal floating point
-static size_t _ftoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags)
-{
-  char buf[PRINTF_FTOA_BUFFER_SIZE];
-  size_t len  = 0U;
-  double diff = 0.0;
-
-  // powers of 10
-  static const double pow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 };
-
-  // test for special values
-  if (value != value)
-    return _out_rev(out, buffer, idx, maxlen, "nan", 3, width, flags);
-  if (value < -DBL_MAX)
-    return _out_rev(out, buffer, idx, maxlen, "fni-", 4, width, flags);
-  if (value > DBL_MAX)
-    return _out_rev(out, buffer, idx, maxlen, (flags & FLAGS_PLUS) ? "fni+" : "fni", (flags & FLAGS_PLUS) ? 4U : 3U, width, flags);
-
-  // test for very large values
-  // standard printf behavior is to print EVERY whole number digit -- which could be 100s of characters overflowing your buffers == bad
-  if ((value > PRINTF_MAX_FLOAT) || (value < -PRINTF_MAX_FLOAT)) {
-#if defined(PRINTF_SUPPORT_EXPONENTIAL)
-    return _etoa(out, buffer, idx, maxlen, value, prec, width, flags);
-#else
-    return 0U;
-#endif
-  }
-
-  // test for negative
-  bool negative = false;
-  if (value < 0) {
-    negative = true;
-    value = 0 - value;
-  }
-
-  // set default precision, if not set explicitly
-  if (!(flags & FLAGS_PRECISION)) {
-    prec = PRINTF_DEFAULT_FLOAT_PRECISION;
-  }
-  // limit precision to 9, cause a prec >= 10 can lead to overflow errors
-  while ((len < PRINTF_FTOA_BUFFER_SIZE) && (prec > 9U)) {
-    buf[len++] = '0';
-    prec--;
-  }
-
-  int whole = (int)value;
-  double tmp = (value - whole) * pow10[prec];
-  unsigned long frac = (unsigned long)tmp;
-  diff = tmp - frac;
-
-  if (diff > 0.5) {
-    ++frac;
-    // handle rollover, e.g. case 0.99 with prec 1 is 1.0
-    if (frac >= pow10[prec]) {
-      frac = 0;
-      ++whole;
-    }
-  }
-  else if (diff < 0.5) {
-  }
-  else if ((frac == 0U) || (frac & 1U)) {
-    // if halfway, round up if odd OR if last digit is 0
-    ++frac;
-  }
-
-  if (prec == 0U) {
-    diff = value - (double)whole;
-    if ((!(diff < 0.5) || (diff > 0.5)) && (whole & 1)) {
-      // exactly 0.5 and ODD, then round up
-      // 1.5 -> 2, but 2.5 -> 2
-      ++whole;
-    }
-  }
-  else {
-    unsigned int count = prec;
-    // now do fractional part, as an unsigned number
-    while (len < PRINTF_FTOA_BUFFER_SIZE) {
-      --count;
-      buf[len++] = (char)(48U + (frac % 10U));
-      if (!(frac /= 10U)) {
-        break;
-      }
-    }
-    // add extra 0s
-    while ((len < PRINTF_FTOA_BUFFER_SIZE) && (count-- > 0U)) {
-      buf[len++] = '0';
-    }
-    if (len < PRINTF_FTOA_BUFFER_SIZE) {
-      // add decimal
-      buf[len++] = '.';
-    }
-  }
-
-  // do whole part, number is reversed
-  while (len < PRINTF_FTOA_BUFFER_SIZE) {
-    buf[len++] = (char)(48 + (whole % 10));
-    if (!(whole /= 10)) {
-      break;
-    }
-  }
-
-  // pad leading zeros
-  if (!(flags & FLAGS_LEFT) && (flags & FLAGS_ZEROPAD)) {
-    if (width && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
-      width--;
-    }
-    while ((len < width) && (len < PRINTF_FTOA_BUFFER_SIZE)) {
-      buf[len++] = '0';
-    }
-  }
-
-  if (len < PRINTF_FTOA_BUFFER_SIZE) {
-    if (negative) {
-      buf[len++] = '-';
-    }
-    else if (flags & FLAGS_PLUS) {
-      buf[len++] = '+';  // ignore the space if the '+' exists
-    }
-    else if (flags & FLAGS_SPACE) {
-      buf[len++] = ' ';
-    }
-  }
-
-  return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags);
-}
-
-
-#if defined(PRINTF_SUPPORT_EXPONENTIAL)
-// internal ftoa variant for exponential floating-point type, contributed by Martijn Jasperse <m.jasperse@gmail.com>
-static size_t _etoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags)
-{
-  // check for NaN and special values
-  if ((value != value) || (value > DBL_MAX) || (value < -DBL_MAX)) {
-    return _ftoa(out, buffer, idx, maxlen, value, prec, width, flags);
-  }
-
-  // determine the sign
-  const bool negative = value < 0;
-  if (negative) {
-    value = -value;
-  }
-
-  // default precision
-  if (!(flags & FLAGS_PRECISION)) {
-    prec = PRINTF_DEFAULT_FLOAT_PRECISION;
-  }
-
-  // determine the decimal exponent
-  // based on the algorithm by David Gay (https://www.ampl.com/netlib/fp/dtoa.c)
-  union {
-    uint64_t U;
-    double   F;
-  } conv;
-
-  conv.F = value;
-  int exp2 = (int)((conv.U >> 52U) & 0x07FFU) - 1023;           // effectively log2
-  conv.U = (conv.U & ((1ULL << 52U) - 1U)) | (1023ULL << 52U);  // drop the exponent so conv.F is now in [1,2)
-  // now approximate log10 from the log2 integer part and an expansion of ln around 1.5
-  int expval = (int)(0.1760912590558 + exp2 * 0.301029995663981 + (conv.F - 1.5) * 0.289529654602168);
-  // now we want to compute 10^expval but we want to be sure it won't overflow
-  exp2 = (int)(expval * 3.321928094887362 + 0.5);
-  const double z  = expval * 2.302585092994046 - exp2 * 0.6931471805599453;
-  const double z2 = z * z;
-  conv.U = (uint64_t)(exp2 + 1023) << 52U;
-  // compute exp(z) using continued fractions, see https://en.wikipedia.org/wiki/Exponential_function#Continued_fractions_for_ex
-  conv.F *= 1 + 2 * z / (2 - z + (z2 / (6 + (z2 / (10 + z2 / 14)))));
-  // correct for rounding errors
-  if (value < conv.F) {
-    expval--;
-    conv.F /= 10;
-  }
-
-  // the exponent format is "%+03d" and largest value is "307", so set aside 4-5 characters
-  unsigned int minwidth = ((expval < 100) && (expval > -100)) ? 4U : 5U;
-
-  // in "%g" mode, "prec" is the number of *significant figures* not decimals
-  if (flags & FLAGS_ADAPT_EXP) {
-    // do we want to fall-back to "%f" mode?
-    if ((value >= 1e-4) && (value < 1e6)) {
-      if ((int)prec > expval) {
-        prec = (unsigned)((int)prec - expval - 1);
-      }
-      else {
-        prec = 0;
-      }
-      flags |= FLAGS_PRECISION;   // make sure _ftoa respects precision
-      // no characters in exponent
-      minwidth = 0U;
-      expval   = 0;
-    }
-    else {
-      // we use one sigfig for the whole part
-      if ((prec > 0) && (flags & FLAGS_PRECISION)) {
-        --prec;
-      }
-    }
-  }
-
-  // will everything fit?
-  unsigned int fwidth = width;
-  if (width > minwidth) {
-    // we didn't fall-back so subtract the characters required for the exponent
-    fwidth -= minwidth;
-  } else {
-    // not enough characters, so go back to default sizing
-    fwidth = 0U;
-  }
-  if ((flags & FLAGS_LEFT) && minwidth) {
-    // if we're padding on the right, DON'T pad the floating part
-    fwidth = 0U;
-  }
-
-  // rescale the float value
-  if (expval) {
-    value /= conv.F;
-  }
-
-  // output the floating part
-  const size_t start_idx = idx;
-  idx = _ftoa(out, buffer, idx, maxlen, negative ? -value : value, prec, fwidth, flags & ~FLAGS_ADAPT_EXP);
-
-  // output the exponent part
-  if (minwidth) {
-    // output the exponential symbol
-    out((flags & FLAGS_UPPERCASE) ? 'E' : 'e', buffer, idx++, maxlen);
-    // output the exponent value
-    idx = _ntoa_long(out, buffer, idx, maxlen, (expval < 0) ? -expval : expval, expval < 0, 10, 0, minwidth-1, FLAGS_ZEROPAD | FLAGS_PLUS);
-    // might need to right-pad spaces
-    if (flags & FLAGS_LEFT) {
-      while (idx - start_idx < width) out(' ', buffer, idx++, maxlen);
-    }
-  }
-  return idx;
-}
-#endif  // PRINTF_SUPPORT_EXPONENTIAL
-#endif  // PRINTF_SUPPORT_FLOAT
-
-
-// internal vsnprintf
-static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const char* format, va_list va)
-{
-  unsigned int flags, width, precision, n;
-  size_t idx = 0U;
-
-  if (!buffer) {
-    // use null output function
-    out = _out_null;
-  }
-
-  while (*format)
-  {
-    // format specifier?  %[flags][width][.precision][length]
-    if (*format != '%') {
-      // no
-      out(*format, buffer, idx++, maxlen);
-      format++;
-      continue;
-    }
-    else {
-      // yes, evaluate it
-      format++;
-    }
-
-    // evaluate flags
-    flags = 0U;
-    do {
-      switch (*format) {
-        case '0': flags |= FLAGS_ZEROPAD; format++; n = 1U; break;
-        case '-': flags |= FLAGS_LEFT;    format++; n = 1U; break;
-        case '+': flags |= FLAGS_PLUS;    format++; n = 1U; break;
-        case ' ': flags |= FLAGS_SPACE;   format++; n = 1U; break;
-        case '#': flags |= FLAGS_HASH;    format++; n = 1U; break;
-        default :                                   n = 0U; break;
-      }
-    } while (n);
-
-    // evaluate width field
-    width = 0U;
-    if (_is_digit(*format)) {
-      width = _atoi(&format);
-    }
-    else if (*format == '*') {
-      const int w = va_arg(va, int);
-      if (w < 0) {
-        flags |= FLAGS_LEFT;    // reverse padding
-        width = (unsigned int)-w;
-      }
-      else {
-        width = (unsigned int)w;
-      }
-      format++;
-    }
-
-    // evaluate precision field
-    precision = 0U;
-    if (*format == '.') {
-      flags |= FLAGS_PRECISION;
-      format++;
-      if (_is_digit(*format)) {
-        precision = _atoi(&format);
-      }
-      else if (*format == '*') {
-        const int prec = (int)va_arg(va, int);
-        precision = prec > 0 ? (unsigned int)prec : 0U;
-        format++;
-      }
-    }
-
-    // evaluate length field
-    switch (*format) {
-      case 'l' :
-        flags |= FLAGS_LONG;
-        format++;
-        if (*format == 'l') {
-          flags |= FLAGS_LONG_LONG;
-          format++;
-        }
-        break;
-      case 'h' :
-        flags |= FLAGS_SHORT;
-        format++;
-        if (*format == 'h') {
-          flags |= FLAGS_CHAR;
-          format++;
-        }
-        break;
-#if defined(PRINTF_SUPPORT_PTRDIFF_T)
-      case 't' :
-        flags |= (sizeof(ptrdiff_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
-        format++;
-        break;
-#endif
-      case 'j' :
-        flags |= (sizeof(intmax_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
-        format++;
-        break;
-      case 'z' :
-        flags |= (sizeof(size_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
-        format++;
-        break;
-      default :
-        break;
-    }
-
-    // evaluate specifier
-    switch (*format) {
-      case 'd' :
-      case 'i' :
-      case 'u' :
-      case 'x' :
-      case 'X' :
-      case 'o' :
-      case 'b' : {
-        // set the base
-        unsigned int base;
-        if (*format == 'x' || *format == 'X') {
-          base = 16U;
-        }
-        else if (*format == 'o') {
-          base =  8U;
-        }
-        else if (*format == 'b') {
-          base =  2U;
-        }
-        else {
-          base = 10U;
-          flags &= ~FLAGS_HASH;   // no hash for dec format
-        }
-        // uppercase
-        if (*format == 'X') {
-          flags |= FLAGS_UPPERCASE;
-        }
-
-        // no plus or space flag for u, x, X, o, b
-        if ((*format != 'i') && (*format != 'd')) {
-          flags &= ~(FLAGS_PLUS | FLAGS_SPACE);
-        }
-
-        // ignore '0' flag when precision is given
-        if (flags & FLAGS_PRECISION) {
-          flags &= ~FLAGS_ZEROPAD;
-        }
-
-        // convert the integer
-        if ((*format == 'i') || (*format == 'd')) {
-          // signed
-          if (flags & FLAGS_LONG_LONG) {
-#if defined(PRINTF_SUPPORT_LONG_LONG)
-            const long long value = va_arg(va, long long);
-            idx = _ntoa_long_long(out, buffer, idx, maxlen, (unsigned long long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
-#endif
-          }
-          else if (flags & FLAGS_LONG) {
-            const long value = va_arg(va, long);
-            idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
-          }
-          else {
-            const int value = (flags & FLAGS_CHAR) ? (char)va_arg(va, int) : (flags & FLAGS_SHORT) ? (short int)va_arg(va, int) : va_arg(va, int);
-            idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned int)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
-          }
-        }
-        else {
-          // unsigned
-          if (flags & FLAGS_LONG_LONG) {
-#if defined(PRINTF_SUPPORT_LONG_LONG)
-            idx = _ntoa_long_long(out, buffer, idx, maxlen, va_arg(va, unsigned long long), false, base, precision, width, flags);
-#endif
-          }
-          else if (flags & FLAGS_LONG) {
-            idx = _ntoa_long(out, buffer, idx, maxlen, va_arg(va, unsigned long), false, base, precision, width, flags);
-          }
-          else {
-            const unsigned int value = (flags & FLAGS_CHAR) ? (unsigned char)va_arg(va, unsigned int) : (flags & FLAGS_SHORT) ? (unsigned short int)va_arg(va, unsigned int) : va_arg(va, unsigned int);
-            idx = _ntoa_long(out, buffer, idx, maxlen, value, false, base, precision, width, flags);
-          }
-        }
-        format++;
-        break;
-      }
-#if defined(PRINTF_SUPPORT_FLOAT)
-      case 'f' :
-      case 'F' :
-        if (*format == 'F') flags |= FLAGS_UPPERCASE;
-        idx = _ftoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
-        format++;
-        break;
-#if defined(PRINTF_SUPPORT_EXPONENTIAL)
-      case 'e':
-      case 'E':
-      case 'g':
-      case 'G':
-        if ((*format == 'g')||(*format == 'G')) flags |= FLAGS_ADAPT_EXP;
-        if ((*format == 'E')||(*format == 'G')) flags |= FLAGS_UPPERCASE;
-        idx = _etoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
-        format++;
-        break;
-#endif  // PRINTF_SUPPORT_EXPONENTIAL
-#endif  // PRINTF_SUPPORT_FLOAT
-      case 'c' : {
-        unsigned int l = 1U;
-        // pre padding
-        if (!(flags & FLAGS_LEFT)) {
-          while (l++ < width) {
-            out(' ', buffer, idx++, maxlen);
-          }
-        }
-        // char output
-        out((char)va_arg(va, int), buffer, idx++, maxlen);
-        // post padding
-        if (flags & FLAGS_LEFT) {
-          while (l++ < width) {
-            out(' ', buffer, idx++, maxlen);
-          }
-        }
-        format++;
-        break;
-      }
-
-      case 's' : {
-        const char* p = va_arg(va, char*);
-        unsigned int l = _strnlen_s(p, precision ? precision : (size_t)-1);
-        // pre padding
-        if (flags & FLAGS_PRECISION) {
-          l = (l < precision ? l : precision);
-        }
-        if (!(flags & FLAGS_LEFT)) {
-          while (l++ < width) {
-            out(' ', buffer, idx++, maxlen);
-          }
-        }
-        // string output
-        while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision--)) {
-          out(*(p++), buffer, idx++, maxlen);
-        }
-        // post padding
-        if (flags & FLAGS_LEFT) {
-          while (l++ < width) {
-            out(' ', buffer, idx++, maxlen);
-          }
-        }
-        format++;
-        break;
-      }
-
-      case 'p' : {
-        width = sizeof(void*) * 2U;
-        flags |= FLAGS_ZEROPAD | FLAGS_UPPERCASE;
-#if defined(PRINTF_SUPPORT_LONG_LONG)
-        const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
-        if (is_ll) {
-          idx = _ntoa_long_long(out, buffer, idx, maxlen, (uintptr_t)va_arg(va, void*), false, 16U, precision, width, flags);
-        }
-        else {
-#endif
-          idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)((uintptr_t)va_arg(va, void*)), false, 16U, precision, width, flags);
-#if defined(PRINTF_SUPPORT_LONG_LONG)
-        }
-#endif
-        format++;
-        break;
-      }
-
-      case '%' :
-        out('%', buffer, idx++, maxlen);
-        format++;
-        break;
-
-      default :
-        out(*format, buffer, idx++, maxlen);
-        format++;
-        break;
-    }
-  }
-
-  // termination
-  out((char)0, buffer, idx < maxlen ? idx : maxlen - 1U, maxlen);
-
-  // return written chars without terminating \0
-  return (int)idx;
-}
-
-
-///////////////////////////////////////////////////////////////////////////////
-
-int printf_(const char* format, ...)
-{
-  va_list va;
-  va_start(va, format);
-  char buffer[1];
-  const int ret = _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
-  va_end(va);
-  return ret;
-}
-
-
-int sprintf_(char* buffer, const char* format, ...)
-{
-  va_list va;
-  va_start(va, format);
-  const int ret = _vsnprintf(_out_buffer, buffer, (size_t)-1, format, va);
-  va_end(va);
-  return ret;
-}
-
-
-int snprintf_(char* buffer, size_t count, const char* format, ...)
-{
-  va_list va;
-  va_start(va, format);
-  const int ret = _vsnprintf(_out_buffer, buffer, count, format, va);
-  va_end(va);
-  return ret;
-}
-
-
-int vprintf_(const char* format, va_list va)
-{
-  char buffer[1];
-  return _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
-}
-
-
-int vsnprintf_(char* buffer, size_t count, const char* format, va_list va)
-{
-  return _vsnprintf(_out_buffer, buffer, count, format, va);
-}
-
-
-int fctprintf(void (*out)(char character, void* arg), void* arg, const char* format, ...)
-{
-  va_list va;
-  va_start(va, format);
-  const out_fct_wrap_type out_fct_wrap = { out, arg };
-  const int ret = _vsnprintf(_out_fct, (char*)(uintptr_t)&out_fct_wrap, (size_t)-1, format, va);
-  va_end(va);
-  return ret;
-}

src/io/term/printf.h

@@ -1,117 +0,0 @@
-///////////////////////////////////////////////////////////////////////////////
-// \author (c) Marco Paland (info@paland.com)
-//             2014-2019, PALANDesign Hannover, Germany
-//
-// \license The MIT License (MIT)
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-// 
-// The above copyright notice and this permission notice shall be included in
-// all copies or substantial portions of the Software.
-// 
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-// THE SOFTWARE.
-//
-// \brief Tiny printf, sprintf and snprintf implementation, optimized for speed on
-//        embedded systems with a very limited resources.
-//        Use this instead of bloated standard/newlib printf.
-//        These routines are thread safe and reentrant.
-//
-///////////////////////////////////////////////////////////////////////////////
-
-#ifndef _PRINTF_H_
-#define _PRINTF_H_
-
-#include <stdarg.h>
-#include <stddef.h>
-
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-
-/**
- * Output a character to a custom device like UART, used by the printf() function
- * This function is declared here only. You have to write your custom implementation somewhere
- * \param character Character to output
- */
-void _putchar(char character);
-
-
-/**
- * Tiny printf implementation
- * You have to implement _putchar if you use printf()
- * To avoid conflicts with the regular printf() API it is overridden by macro defines
- * and internal underscore-appended functions like printf_() are used
- * \param format A string that specifies the format of the output
- * \return The number of characters that are written into the array, not counting the terminating null character
- */
-#define printf printf_
-int printf_(const char* format, ...);
-
-
-/**
- * Tiny sprintf implementation
- * Due to security reasons (buffer overflow) YOU SHOULD CONSIDER USING (V)SNPRINTF INSTEAD!
- * \param buffer A pointer to the buffer where to store the formatted string. MUST be big enough to store the output!
- * \param format A string that specifies the format of the output
- * \return The number of characters that are WRITTEN into the buffer, not counting the terminating null character
- */
-#define sprintf sprintf_
-int sprintf_(char* buffer, const char* format, ...);
-
-
-/**
- * Tiny snprintf/vsnprintf implementation
- * \param buffer A pointer to the buffer where to store the formatted string
- * \param count The maximum number of characters to store in the buffer, including a terminating null character
- * \param format A string that specifies the format of the output
- * \param va A value identifying a variable arguments list
- * \return The number of characters that COULD have been written into the buffer, not counting the terminating
- *         null character. A value equal or larger than count indicates truncation. Only when the returned value
- *         is non-negative and less than count, the string has been completely written.
- */
-#define snprintf  snprintf_
-#define vsnprintf vsnprintf_
-int  snprintf_(char* buffer, size_t count, const char* format, ...);
-int vsnprintf_(char* buffer, size_t count, const char* format, va_list va);
-
-
-/**
- * Tiny vprintf implementation
- * \param format A string that specifies the format of the output
- * \param va A value identifying a variable arguments list
- * \return The number of characters that are WRITTEN into the buffer, not counting the terminating null character
- */
-#define vprintf vprintf_
-int vprintf_(const char* format, va_list va);
-
-
-/**
- * printf with output function
- * You may use this as dynamic alternative to printf() with its fixed _putchar() output
- * \param out An output function which takes one character and an argument pointer
- * \param arg An argument pointer for user data passed to output function
- * \param format A string that specifies the format of the output
- * \return The number of characters that are sent to the output function, not counting the terminating null character
- */
-int fctprintf(void (*out)(char character, void* arg), void* arg, const char* format, ...);
-
-
-#ifdef __cplusplus
-}
-#endif
-
-
-#endif  // _PRINTF_H_

src/io/term/term.c

@@ -13,24 +13,151 @@ because this shitty implementation will be replaced one day by Flanterm
 
 #include <stddef.h>
 #include <kernel.h>
-#include "term.h"
+#include <io/term/term.h>
-#include "config.h"
+#include <config.h>
-#include "flanterm.h"
+#include <io/term/flanterm.h>
-#include "flanterm_backends/fb.h"
+#include <io/term/flanterm_backends/fb.h>
-#include "mem/heap/kheap.h"
+#include <mem/kheap.h>
-#include "limine.h"
+#include <limine.h>
+#include <stdarg.h>
+#include <sched/spinlock.h>
+#include <io/serial/serial.h>
+
+#define NANOPRINTF_IMPLEMENTATION
+#include <io/term/nanoprintf.h>
 
 extern struct flanterm_context* ft_ctx;
 extern struct init_status init;
 
+struct spinlock term_lock = {0};
+struct spinlock printf_lock = {0};
+
+extern int panic_count;
+
 /*
- * _putchar - Writes a character to terminal
+ * internal_putc - Internal putchar function
- * @character: character to write
+ * @c: char to print
+ * @_: (unused, for nanoprintf)
+ *
+ * Prints a character to the terminal if it's ready,
+ * and also to the serial interface if it's ready.
  */
-void _putchar(char character)
+void internal_putc(int c, void *_)
 {
-	// TODO: Spinlock here (terminal access)
+    (void)_;
-	flanterm_write(ft_ctx, &character, 1);
+    char ch = (char)c;
+
+    if (init.terminal) {
+        if (panic_count == 0) {
+            spinlock_acquire(&term_lock);
+            flanterm_write(ft_ctx, &ch, 1);
+            spinlock_release(&term_lock);
+        } else {
+            flanterm_write(ft_ctx, &ch, 1);
+        }
+    }
+
+    if (init.serial) {
+        if (ch == '\n') {
+            skputc('\r');
+        }
+        skputc(ch);
+    }
+}
+
+/*
+ * debug_putc - Internal DEBUG putchar function
+ * @c: char to print
+ * @_: (unused, for nanoprintf)
+ *
+ * Prints a character to the terminal if it's ready and if 
+ * the kernel is still initializing, and also always to the
+ * serial interface if it's ready.
+ */
+void debug_putc(int c, void *_)
+{
+    (void)_;
+    char ch = (char)c;
+
+    if (init.terminal && (!init.all || panic_count > 0)) {
+        if (panic_count == 0) {
+            spinlock_acquire(&term_lock);
+            flanterm_write(ft_ctx, &ch, 1);
+            spinlock_release(&term_lock);
+        } else {
+            flanterm_write(ft_ctx, &ch, 1);
+        }
+    }
+
+    if (init.serial) {
+        if (ch == '\n') {
+            skputc('\r');
+        }
+        skputc(ch);
+    }
+}
+
+/*
+ * printf - Fromatted printing
+ * @fmt: format string
+ * @...: variadic arguments
+ *
+ * Wrapper for nanoprintf
+ *
+ * Return:
+ * <ret> - number of characters sent to the callback
+ * %-1   - error
+ */
+int printf(const char* fmt, ...)
+{
+    if (panic_count == 0) {
+        spinlock_acquire(&printf_lock);
+        va_list args;
+        va_start(args, fmt);
+        int ret = npf_vpprintf(internal_putc, NULL, fmt, args);
+        va_end(args);
+        spinlock_release(&printf_lock);
+        return ret;
+    } else {
+        va_list args;
+        va_start(args, fmt);
+        int ret = npf_vpprintf(internal_putc, NULL, fmt, args);
+        va_end(args);
+        return ret;
+    }
+    return -1;
+}
+
+/*
+ * kprintf - Fromatted DEBUG printing 
+ * @fmt: format string
+ * @...: variadic arguments
+ *
+ * Wrapper for nanoprintf; to be used only for
+ * kernel/debug messages.
+ *
+ * Return:
+ * <ret> - number of characters sent to the callback
+ * %-1   - error
+ */
+int kprintf(const char* fmt, ...)
+{
+    if (panic_count == 0) {
+        spinlock_acquire(&printf_lock);
+        va_list args;
+        va_start(args, fmt);
+        int ret = npf_vpprintf(debug_putc, NULL, fmt, args);
+        va_end(args);
+        spinlock_release(&printf_lock);
+        return ret;
+    } else {
+        va_list args;
+        va_start(args, fmt);
+        int ret = npf_vpprintf(debug_putc, NULL, fmt, args);
+        va_end(args);
+        return ret;
+    }
+    return -1;
 }
 
 /*
@@ -43,30 +170,14 @@ void kputs(const char* str)
 {
 	size_t i=0;
 	while (str[i] != 0) {
-		_putchar(str[i]);
+		internal_putc(str[i], NULL);
 		i++;
 	}
-	_putchar('\r');
 }
 
 extern struct flanterm_context* ft_ctx;
 extern struct boot_context boot_ctx;
 
-/*
- * flanterm_free_wrapper - free() wrapper for Flanterm 
- * @ptr:  pointer to free
- * @size: amount of bytes to free
- *
- * This function exists solely because the Flanterm initialization
- * function only accepts a free() function with a size parameter,
- * and the default one doesn't have it.
- */
-void flanterm_free_wrapper(void* ptr, size_t size)
-{
-	(void)size;
-	kfree(ptr);
-}
-
 /*
  * term_init - Video output/terminal initialization
  *
@@ -76,8 +187,8 @@ void term_init()
 {
 	uint32_t bgColor = 0x252525;
 	ft_ctx = flanterm_fb_init(
-        kmalloc,
+        NULL,
-        flanterm_free_wrapper,
+        NULL,
         boot_ctx.fb->address, boot_ctx.fb->width, boot_ctx.fb->height, boot_ctx.fb->pitch,
         boot_ctx.fb->red_mask_size, boot_ctx.fb->red_mask_shift,
         boot_ctx.fb->green_mask_size, boot_ctx.fb->green_mask_shift,

src/kapps/kshell.c

@@ -0,0 +1,112 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   PepperOS kernel shell
+ * @license GPL-3.0-only
+ */
+
+#include "fs/initfs.h"
+#include <io/term/term.h>
+#include <config.h>
+#include <io/kbd/ps2.h>
+#include <string/string.h>
+#include <stdint.h>
+#include <kernel.h>
+#include <time/date.h>
+#include <mem/kheap.h>
+
+__attribute__((noinline))
+void smash_it()
+{
+    char buf[16]; (void)buf;
+    for (size_t i=0; i<256; i++) {
+        buf[i] = (char)i;
+    }
+}
+
+/*
+ * pedicel_main - Kernel shell main function
+ * @arg: argument (optional)
+ *
+ * This is the entry point for the kernel shell process.
+ * It is used to start programs and to test different things
+ * on different real hardware easily.
+ *
+ * Named after the root part of the pepper.
+ */
+void pedicel_main(void* arg)
+{
+    printf("Welcome to the kernel shell!\r\nType 'help' for a list of commands.\r\n");
+
+    for (;;) {
+        char input_buf[PEDICEL_INPUT_SIZE] = {0};
+        printf(PEDICEL_PROMPT);
+        keyboard_getline(input_buf, PEDICEL_INPUT_SIZE);
+        
+        if (strncmp(input_buf, "help", 4) == 0) {
+            printf("++ shell builtins ++\r\n\r\n"
+                            "\tclear   - clear the screen\r\n"
+                            "\tpanic   - trigger a test panic\r\n"
+                            "\tsyscall - trigger int 0x80\r\n"
+                            "\tpf      - trigger a page fault\r\n"
+                            "\tnow     - get current date\r\n"
+                            "\tsmash   - smash the stack\r\n"
+                            "\tmem     - get used heap info\r\n"
+                            "\tload    - load an user executable\r\n"
+                            "\tlist    - list initfs.tar contents\r\n");
+            continue;
+        }
+
+        if (strncmp(input_buf, "", 1) == 0) {
+            continue;
+        } 
+
+        if (strncmp(input_buf, "clear", 5) == 0) {
+            printf("\x1b[2J\x1b[H");
+            continue;
+        }
+
+        if (strncmp(input_buf, "panic", 5) == 0) {
+            panic(NULL, "test panic");
+        }
+
+        if (strncmp(input_buf, "syscall", 7) == 0) {
+            __asm__ volatile("mov $0x00, %rdi");
+            __asm__ volatile("int $0x80");
+            continue;
+        }
+
+        if (strncmp(input_buf, "pf", 2) == 0) {
+            volatile uint64_t* fault = (uint64_t*)0xdeadbeef;
+            fault[0] = 1;
+        }
+
+        if (strncmp(input_buf, "now", 3) == 0) {
+            struct date now = date_now();
+            printf("Now is %02u:%02u:%02u on %u/%u/%u\r\n", now.hour, now.minute,
+                now.second, now.day, now.month, now.year);
+            continue;
+        }
+
+        if (strncmp(input_buf, "smash", 5) == 0) {
+            smash_it();
+            continue;
+        }
+
+        if (strncmp(input_buf, "mem", 3) == 0) {
+            kheap_info();
+            continue;
+        }
+
+        if (strncmp(input_buf, "load", 4) == 0) {
+            loader_load_raw();
+            continue;
+        }
+
+        if (strncmp(input_buf, "list", 4) == 0) {
+            tar_list();
+            continue;
+        }
+
+        printf("%s: command not found\r\n", input_buf);
+    }
+}

src/kapps/loader.c

@@ -0,0 +1,32 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Executable loader
+ * @license GPL-3.0-only
+ */         
+
+#include <stddef.h>
+#include <fs/initfs.h>
+#include <kernel.h>
+#include <sched/process.h>
+#include <io/kbd/ps2.h>
+#include <string/string.h>
+
+extern void* archive_start_addr;
+
+int loader_load_raw()
+{
+    char input_buf[PEDICEL_INPUT_SIZE] = {0};
+    do {
+        printf("file> ");
+        keyboard_getline(input_buf, PEDICEL_INPUT_SIZE);   
+    } while (strncmp(input_buf, "", 1) == 0);
+
+    char* data = NULL;
+    int sz = tar_lookup(archive_start_addr, input_buf,&data);
+    if (sz > 0) {
+        process_create_user_raw(data, sz, input_buf);
+        return 0; // TODO: should return something else on error
+    }
+    printf("Couldn't load file '%s'\r\n", input_buf);
+    return 1;
+}

src/kmain.c

@@ -7,29 +7,32 @@
 #include <stdbool.h>	
 #include <stddef.h>
 #include <limine.h>
-#include "io/term/term.h"
+#include <io/term/term.h>
-#include "io/term/printf.h"
+#include <io/serial/serial.h>
-#include "io/serial/serial.h"
+#include <arch/gdt.h>
-#include "mem/gdt/gdt.h"
+#include <mem/utils.h>
-#include "mem/misc/utils.h"
+#include <kernel.h>
-#include "idt/idt.h"
+#include <time/timer.h>
-#include "kernel.h"
+#include <io/kbd/ps2.h>
-#include "time/timer.h"
+#include <mem/pmm.h>
-#include "io/kbd/ps2.h"
+#include <mem/paging.h>
-#include "mem/paging/pmm.h"
+#include <mem/vmm.h>
-#include "mem/paging/paging.h"
+#include <mem/kheap.h>
-#include "mem/paging/vmm.h"
+#include <sched/process.h>
-#include "mem/heap/kheap.h"
+#include <sched/scheduler.h>
-#include "sched/process.h"
+#include <config.h>
-#include "sched/scheduler.h"
+#include <io/term/flanterm.h>
-#include "config.h"
+#include <io/term/flanterm_backends/fb.h>
-#include "io/term/flanterm.h"
+#include <arch/x86.h>
-#include "io/term/flanterm_backends/fb.h"
+#include <boot/boot.h>
+#include <fs/initfs.h>
 
 // Limine version used
 __attribute__((used, section(".limine_requests")))
 volatile LIMINE_BASE_REVISION(3);
 
+int panic_count = 0;
+
 /*
  * hcf - Halt and catch fire
  *
@@ -59,16 +62,14 @@ extern volatile struct limine_framebuffer_request framebuffer_request;
 extern volatile struct limine_memmap_request memmap_request;
 extern volatile struct limine_hhdm_request hhdm_request;
 extern volatile struct limine_kernel_address_request kerneladdr_request;
+extern volatile struct limine_boot_time_request date_request;
+extern volatile struct limine_module_request module_request;
 
-extern struct process_t* processes_list;
+struct limine_file* file;
-extern struct process_t* current_process;
-struct process_t* idle_proc;
 
-// Never gets executed although pedicel is scheduled?
+extern struct process* processes_list;
-void pedicel_main(void* arg)
+extern struct process* current_process;
-{
+struct process* idle_proc;
-	printf("\n\nWelcome to PepperOS! Pedicel speaking.\r\nNothing left to do, let's go idle!");
-}
 
 void idle_main(void* arg)
 {
@@ -92,38 +93,37 @@ void kmain()
 	CLEAR_INTERRUPTS;
 	if (!LIMINE_BASE_REVISION_SUPPORTED) hcf();
 
+	populate_boot_context(&boot_ctx);
+
+	term_init();
 	serial_init();
 	timer_init();
 
-	// Populate boot context
+	x86_arch_init();
- 	boot_ctx.fb = framebuffer_request.response ? framebuffer_request.response->framebuffers[0] : NULL;
-	boot_ctx.mmap = memmap_request.response ? memmap_request.response : NULL;
-	boot_ctx.hhdm = hhdm_request.response ? hhdm_request.response : NULL;
-	boot_ctx.kaddr = kerneladdr_request.response ? kerneladdr_request.response : NULL;
 
 	boot_mem_display();
 	pmm_init(boot_ctx);
 
-	// Remap kernel , HHDM and framebuffer
 	paging_init(boot_ctx);
 	kheap_init();
 
 	keyboard_init(FR);
 	
-	term_init();
-
-	gdt_init();
-	idt_init();
-	
 	process_init();
 	idle_proc = process_create("idle", (void*)idle_main, 0);
-	struct process_t* pedicel = process_create("pedicel", (void*)pedicel_main, 0);
 
-	process_display_list(processes_list);
+	if (!boot_ctx.module) {
+		panic(NULL, "could not load initfs.tar :(");
+	}
+	if (boot_ctx.module->module_count == 1) {
+		initfs_init(boot_ctx.module->modules[0]);
+	}
 	
+	process_create("kshell", (void*)pedicel_main, 0);
 	scheduler_init();
 
-	kputs(PEPPEROS_SPLASH);
+	printf(PEPPEROS_SPLASH);
+	init.all = true;
 
 	idle();
 }

src/mem/gdt/gdt.c

@@ -1,107 +0,0 @@
-/*
- * @author  xamidev <xamidev@riseup.net>
- * @brief   Global Descriptor Table (for legacy reasons)
- * @license GPL-3.0-only
- */
-
-#include "gdt.h"
-#include <stdint.h>
-#include "io/serial/serial.h"
-#include <kernel.h>
-
-// Descriptors are 8-byte wide (64bits)
-// So the selectors will be (in bytes): 0x0, 0x8, 0x10, 0x18, etc..
-uint64_t gdt_entries[NUM_GDT_ENTRIES];
-struct GDTR gdtr;
-
-/*
- * gdt_load - Loads Global Descriptor Table
- */
-static void gdt_load()
-{
-    asm("lgdt %0" : : "m"(gdtr));
-}
-
-/*
- * gdt_flush - Flushes the Global Descriptor Table
- *
- * This function loads new Segment Selectors to make
- * the GDT changes take effect
- */
-static void gdt_flush()
-{
-    // Here, 0x8 is the kernel code selector
-    // and 0x10 is the kernel data selector
-    asm volatile (
-        "mov $0x10, %%ax \n" // Reload segments with kernel data selector
-        "mov %%ax, %%ds \n"
-        "mov %%ax, %%es \n"
-        "mov %%ax, %%fs \n"
-        "mov %%ax, %%gs \n"
-        "mov %%ax, %%ss \n"
-
-        "pushq $0x8      \n"   // CS reload
-        "lea 1f(%%rip), %%rax \n"
-        "push %%rax     \n"
-        "lretq          \n"
-        "1:             \n" // Execution continues here after CS reload
-        :
-        :
-        : "rax", "memory"
-    );
-}
-
-/*
- * gdt_init - Global Descriptor Table initialization 
- *
- * This function loads a new GDT in the CPU.
- * It contains a null descriptor, kernel code and data
- * segments, and user code and data segments.
- * However, we do not use segmentation to manage memory on
- * 64-bit x86, as it's deprecated. Instead, we use paging. 
- */
-void gdt_init()
-{
-    // Null descriptor (required)
-    gdt_entries[0] = 0;
-
-    // Kernel code segment
-    uint64_t kernel_code = 0;
-    kernel_code |= 0b1101 << 8; // Selector type: accessed, read-enable, no conforming
-    kernel_code |= 1 << 12; // not a system descriptor
-    kernel_code |= 0 << 13; // DPL field = 0
-    kernel_code |= 1 << 15; // Present
-    kernel_code |= 1 << 21; // Long mode
-
-    // Left shift 32 bits so we place our stuff in the upper 32 bits of the descriptor.
-    // The lower 32 bits contain limit and part of base and therefore are ignored in Long Mode
-    // (because we'll use paging; segmentation is used only for legacy)
-    gdt_entries[1] = kernel_code << 32;
-
-    uint64_t kernel_data = 0;
-    kernel_data |= 0b0011 << 8;
-    kernel_data |= 1 << 12;
-    kernel_data |= 0 << 13;
-    kernel_data |= 1 << 15;
-    kernel_data |= 1 << 21;
-
-    gdt_entries[2] = kernel_data << 32;
-
-    // We re-use the kernel descriptors here, and just update their DPL fields
-    // (Descriptor privilege level) from ring 0 -> to ring 3 (userspace)
-    uint64_t user_code = kernel_code | (3 << 13);
-    gdt_entries[3] = user_code;
-
-    uint64_t user_data = kernel_data | (3 << 13);
-    gdt_entries[4] = user_data;
-
-    // The -1 subtraction is some wizardry explained in the OSDev wiki -> GDT
-    gdtr.limit = NUM_GDT_ENTRIES * sizeof(uint64_t) - 1;
-    gdtr.address = (uint64_t)gdt_entries;
-
-    // Load the GDT we created, flush the old one
-    gdt_load();
-    gdt_flush();
-
-    DEBUG("GDT initialized");
-}

src/mem/kheap.c

@@ -4,20 +4,20 @@
  * @license GPL-3.0-only
  */
 
-#include "kheap.h"
+#include <mem/kheap.h>
-#include "mem/paging/paging.h"
+#include <mem/paging.h>
-#include "mem/paging/pmm.h"
+#include <mem/pmm.h>
 #include <stddef.h>
 #include <kernel.h>
-#include "sched/process.h"
+#include <sched/process.h>
-#include "config.h"
+#include <config.h>
 
 extern uint64_t kernel_phys_base;
 extern uint64_t kernel_virt_base;
 
 uintptr_t kheap_start;
 
-static struct heap_block_t* head = NULL;
+static struct heap_block* head = NULL;
 static uintptr_t end;
 
 // Kernel root table (level 4)
@@ -55,8 +55,8 @@ void kheap_init()
     end = current_addr;
 
     // Give linked list head its properties
-    head = (struct heap_block_t*)kheap_start;
+    head = (struct heap_block*)kheap_start;
-    head->size = (end-kheap_start) - sizeof(struct heap_block_t);
+    head->size = (end-kheap_start) - sizeof(struct heap_block);
     head->free = true;
     head->next = NULL;
     DEBUG("Kernel heap initialized, head=0x%p, size=%u bytes", head, head->size);
@@ -80,16 +80,16 @@ void* kmalloc(size_t size)
     if (!size) return NULL;
     size = ALIGN(size);
 
-    struct heap_block_t* curr = head;
+    struct heap_block* curr = head;
 
     while (curr) {
         // Is block free and big enough for us?
         if (curr->free && curr->size >= size) {
             // We split the block if it is big enough
-            if (curr->size >= size + sizeof(struct heap_block_t) + 16) {
+            if (curr->size >= size + sizeof(struct heap_block) + 16) {
-                struct heap_block_t* split = (struct heap_block_t*)((uintptr_t)curr + sizeof(struct heap_block_t) + size);
+                struct heap_block* split = (struct heap_block*)((uintptr_t)curr + sizeof(struct heap_block) + size);
                 
-                split->size = curr->size - size - sizeof(struct heap_block_t);
+                split->size = curr->size - size - sizeof(struct heap_block);
                 split->free = true;
                 split->next = curr->next;
 
@@ -99,7 +99,7 @@ void* kmalloc(size_t size)
 
             // Found a good block, we return it
             curr->free = false;
-            return (void*)((uintptr_t)curr + sizeof(struct heap_block_t));
+            return (void*)((uintptr_t)curr + sizeof(struct heap_block));
         }
         // Continue browsing the list if nothing good was found yet
         curr = curr->next;
@@ -127,11 +127,11 @@ void kfree(void* ptr)
     if (!ptr) return;
 
     // Set it free!
-    struct heap_block_t* block = (struct heap_block_t*)((uintptr_t)ptr - sizeof(struct heap_block_t));
+    struct heap_block* block = (struct heap_block*)((uintptr_t)ptr - sizeof(struct heap_block));
     block->free = true;
 
     // merge adjacent free blocks (coalescing)
-    struct heap_block_t* curr = head;
+    struct heap_block* curr = head;
     while (curr && curr->next) {
         if (curr->free && curr->next->free) {
             curr->size += sizeof(*curr) + curr->next->size;
@@ -158,3 +158,32 @@ void* kalloc_stack()
     uint8_t* ptr = kmalloc(PROCESS_STACK_SIZE); // As it's out of kmalloc, stack is already mapped into kernel space
     return ptr ? ptr+PROCESS_STACK_SIZE : NULL;
 }
+
+/*
+ * kheap_info - Display heap info
+ *
+ * This function writes the size of the heap (total),
+ * the number of allocated bytes, and the number of
+ * free bytes to the standard output.
+ */
+void kheap_info()
+{
+    uint64_t free_bytes = 0;
+    struct heap_block* curr = (struct heap_block*)kheap_start;
+
+    while (curr) {
+        if (curr->free == true) {
+            free_bytes += curr->size;
+        }
+        curr = curr->next;
+    }
+
+    uint64_t total = end-kheap_start;
+
+    printf("total=% 8u bytes (%u kB)\r\n"
+                "alloc=% 8u bytes (%u kB)\r\n"
+                " free=% 8u bytes (%u kB)\r\n",
+                total, (total)/1000,
+                total-free_bytes, (total-free_bytes)/1000,
+                free_bytes, free_bytes/1000);
+}

src/mem/paging.c

@@ -4,12 +4,12 @@
  * @license GPL-3.0-only
  */
 
-#include "paging.h"
+#include <mem/paging.h>
-#include "pmm.h"
+#include <mem/pmm.h>
 #include <kernel.h>
 #include <stddef.h>
 #include <limine.h>
-#include "config.h"
+#include <config.h>
 
 /*
 Paging on x86 uses four different page table levels:
@@ -43,7 +43,7 @@ void load_cr3(uint64_t value) {
  * This function is used to flush at least the TLB entrie(s)
  * for the page that contains the <addr> address.
  */
-static inline void invlpg(void *addr)
+void invlpg(void *addr)
 {
     asm volatile("invlpg (%0)" :: "r"(addr) : "memory");
 }
@@ -59,7 +59,7 @@ static inline void invlpg(void *addr)
  * Return:
  * <virt> - Pointer to allocated page table
  */
-static uint64_t* alloc_page_table()
+uint64_t* alloc_page_table()
 {
     uint64_t* virt = (uint64_t*)PHYS_TO_VIRT(pmm_alloc());
 
@@ -99,30 +99,46 @@ void paging_map_page(uint64_t* root_table, uint64_t virt, uint64_t phys, uint64_
 
     uint64_t *pdpt, *pd, *pt;
 
+    // Any parent entry on a userspace mapping must also carry PTE_USER,
+    // otherwise CPL3 accesses fault even if the final PTE is user.
+    uint64_t parent_flags = PTE_PRESENT | PTE_WRITABLE;
+    if (flags & PTE_USER) {
+        parent_flags |= PTE_USER;
+    }
+
     // PML4
     // If the entry at index is not present, allocate enough space for it
     // then populate the entry with correct addr + flags
     if (!(root_table[pml4_i] & PTE_PRESENT)) {
         pdpt = alloc_page_table();
-        root_table[pml4_i] = VIRT_TO_PHYS(pdpt) | PTE_PRESENT | PTE_WRITABLE;
+        root_table[pml4_i] = VIRT_TO_PHYS(pdpt) | parent_flags;
     } else {
         pdpt = (uint64_t *)PHYS_TO_VIRT(root_table[pml4_i] & PTE_ADDR_MASK);
+        if (flags & PTE_USER) {
+            root_table[pml4_i] |= PTE_USER;
+        }
     }
 
     // PDPT: same here
     if (!(pdpt[pdpt_i] & PTE_PRESENT)) {
         pd = alloc_page_table();
-        pdpt[pdpt_i] = VIRT_TO_PHYS(pd) | PTE_PRESENT | PTE_WRITABLE;
+        pdpt[pdpt_i] = VIRT_TO_PHYS(pd) | parent_flags;
     } else {
         pd = (uint64_t *)PHYS_TO_VIRT(pdpt[pdpt_i] & PTE_ADDR_MASK);
+        if (flags & PTE_USER) {
+            pdpt[pdpt_i] |= PTE_USER;
+        }
     }
 
     // PD: and here
     if (!(pd[pd_i] & PTE_PRESENT)) {
         pt = alloc_page_table();
-        pd[pd_i] = VIRT_TO_PHYS(pt) | PTE_PRESENT | PTE_WRITABLE;
+        pd[pd_i] = VIRT_TO_PHYS(pt) | parent_flags;
     } else {
         pt = (uint64_t *)PHYS_TO_VIRT(pd[pd_i] & PTE_ADDR_MASK);
+        if (flags & PTE_USER) {
+            pd[pd_i] |= PTE_USER;
+        }
     }
 
     // PT: finally, populate the page table entry
@@ -173,9 +189,9 @@ void paging_init(struct boot_context boot_ctx)
         }
     }
 
-    // 4GB
+    // 8GB
     if (max_phys > PAGING_MAX_PHYS) {
-        DEBUG("WARNING: max_phys capped to 4GB (%x) (from max_phys=%p)", PAGING_MAX_PHYS, max_phys);
+        DEBUG("WARNING: max_phys capped to PAGING_MAX_PHYS (from max_phys=%p)", max_phys);
         max_phys = PAGING_MAX_PHYS;
     }
 
@@ -202,9 +218,9 @@ void paging_init(struct boot_context boot_ctx)
     uint64_t fb_size = fb->pitch * fb->height;
     uint64_t fb_pages = (fb_size + PAGE_SIZE-1)/PAGE_SIZE;
 
-    // Map the framebuffer (with cache-disable & write-through)
+    // Map the framebuffer (PWT set, and no PCD means PAT1 [Write-Combining] for this region)
     for (uint64_t i=0; i<fb_pages; i++) {
-        paging_map_page(kernel_pml4, fb_virt+i*PAGE_SIZE, fb_phys+i*PAGE_SIZE, PTE_WRITABLE | PTE_PCD | PTE_PWT);
+        paging_map_page(kernel_pml4, fb_virt+i*PAGE_SIZE, fb_phys+i*PAGE_SIZE, PTE_WRITABLE | PTE_PWT);
         page_count++;
     }
     DEBUG("Mapped %u pages for framebuffer", page_count);

src/mem/paging/vmm.c

@@ -1,81 +0,0 @@
-/*
- * @author  xamidev <xamidev@riseup.net>
- * @brief   Virtual memory manager
- * @license GPL-3.0-only
- */
-
-/*
-The VMM (virtual memory manager) will have two roles:
-- mapping pages
-- unmapping pages
-in a specified virtual space
-
-compared to the PMM which allocs/frees 4kb frames ("physical pages").
-*/
-
-#include "vmm.h"
-#include "paging.h"
-#include <stddef.h>
-#include "pmm.h"
-#include <kernel.h>
-
-void* vmm_pt_root = 0;
-
-// Linked list head for virtual memory objects
-struct vm_object* vm_objs = NULL;
-
-/*
- * Will have to be rewritten and expanded,
- * to prepare for userspace.
- * The platform-agnostic flags will be removed
- * because as long as the kernel is x86 only,
- * we don't need over complication.
- * Plus I don't plan to port to other architectures
-*/
-
-uint64_t convert_x86_vm_flags(size_t flags)
-{
-    uint64_t value = 0;
-    if (flags & VM_FLAG_WRITE)
-    {
-        value |= PTE_WRITABLE;
-    }
-    if (flags & VM_FLAG_USER)
-    {
-        value |= PTE_USER;
-    }
-    if ((flags & VM_FLAG_EXEC) == 0)
-    {
-        value |= PTE_NOEXEC;
-    }
-    return value;
-}
-
-extern uint64_t *kernel_pml4;
-
-void vmm_setup_pt_root()
-{
-    // We alloc a physical page (frame) for the pointer, then map it
-    // to virt (pointer)
-    uintptr_t phys = pmm_alloc();
-    vmm_pt_root = (void*)kernel_pml4;
-    paging_map_page(kernel_pml4, (uint64_t)vmm_pt_root, phys, convert_x86_vm_flags(VM_FLAG_WRITE | VM_FLAG_EXEC));
-    DEBUG("VMM setup: vmm_pt_root=0x%p (phys=0x%p)", vmm_pt_root, phys);
-}
-
-/* void* vmm_alloc(size_t length, size_t flags)
-{
-    // We will try to allocate at least length bytes, which have to be rounded UP to
-    // the next page so its coherent with the PMM
-    size_t len = ALIGN_UP(length, PAGE_SIZE);
-
-    // Need to implement this (as linked list)
-    // but for now kernel heap is sufficient
-    // The VMM will prob be more useful when we have userspace
-} */
-
-void vmm_init()
-{
-    // NO U
-    //vmm_setup_pt_root();
-}

src/mem/paging/vmm.h

@@ -1,34 +0,0 @@
-/*
- * @author  xamidev <xamidev@riseup.net>
- * @brief   Virtual memory manager
- * @license GPL-3.0-only
- */
-
-#ifndef VMM_H
-#define VMM_H
-
-#include <stdint.h>
-#include <stddef.h>
-
-/*
-This will be our linked list of virtual memory objects.
-Flags here aren't x86 flags, they are platform-agnostic
-kernel-defined flags.
-*/
-
-struct vm_object {
-    uintptr_t base;
-    size_t length;
-    size_t flags;
-    struct vm_object* next;
-};
-
-// Flags bitfield
-#define VM_FLAG_NONE 0
-#define VM_FLAG_WRITE (1 << 0)
-#define VM_FLAG_EXEC (1 << 1)
-#define VM_FLAG_USER (1 << 2)
-
-void vmm_init(void);
-
-#endif

src/mem/pmm.c

@@ -11,55 +11,20 @@ it will probably need to get some info from Limine,
 to see which pages are used by kernel/bootloader/mmio/fb etc.
 */
 
-#include "paging.h"
+#include "config.h"
+#include <mem/paging.h>
 #include <limine.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <kernel.h>
-#include "mem/misc/utils.h"
+#include <mem/utils.h>
-#include "pmm.h"
+#include <mem/pmm.h>
 
 /*
 First we'll have to discover the physical memory layout,
 and for that we can use a Limine request.
 */
 
-struct limine_memmap_entry* biggest_entry;
-
-/*
- * pmm_find_biggest_usable_region - Finding the biggest free memory region
- * @memmap: Limine memory map
- * @hhdm:   Limine HHDM offset
- *
- * This function uses the memory map provided by the bootloader
- * to find the single biggest free memory region we can use.
- */
-static void pmm_find_biggest_usable_region(struct limine_memmap_response* memmap, struct limine_hhdm_response* hhdm)
-{
-    // Max length of a usable memory region
-    uint64_t length_max = 0;
-    uint64_t offset = hhdm->offset;
-
-    DEBUG("Usable Memory:");
-    for (size_t i=0; i<memmap->entry_count; i++) {
-        struct limine_memmap_entry* entry = memmap->entries[i];
-
-        if (entry->type == LIMINE_MEMMAP_USABLE) {
-            DEBUG("0x%p-0x%p mapped at 0x%p-0x%p", entry->base, entry->base+entry->length,
-                        entry->base+offset, entry->base+entry->length+offset);
-            if (entry->length > length_max)
-            {
-                length_max = entry->length;
-                biggest_entry = entry;
-            }
-        }
-    }
-
-    DEBUG("Biggest usable memory region:");
-    DEBUG("0x%p-0x%p mapped at 0x%p-0x%p", biggest_entry->base, biggest_entry->base + biggest_entry->length,
-            biggest_entry->base+offset, biggest_entry->base+biggest_entry->length+offset);
-}
-
 // Offset from Higher Half Direct Map
 uint64_t hhdm_off;
 
@@ -99,19 +64,32 @@ void pmm_free(uintptr_t addr)
  * This function marks the biggest memory region as
  * free, so we can use it in pmm_alloc.
  */
-static void pmm_init_freelist()
+static void pmm_init_freelist(struct limine_memmap_response* memmap)
 {
-    // We simply call pmm_free() on each page that is marked USABLE
+    uint64_t total_pages = 0;
-    // in our big memory region.
+
-    uint64_t base = ALIGN_UP(biggest_entry->base, PAGE_SIZE);
+    for (size_t i=0; i<memmap->entry_count; i++) {
-    uint64_t end = ALIGN_DOWN(biggest_entry->base + biggest_entry->length, PAGE_SIZE);
+        struct limine_memmap_entry* entry = memmap->entries[i];
+
+        if (entry->type == LIMINE_MEMMAP_USABLE) {
+            uint64_t base = ALIGN_UP(entry->base, PAGE_SIZE);
+            uint64_t end = ALIGN_DOWN(entry->base + entry->length, PAGE_SIZE);
+
+            if (end > PAGING_MAX_PHYS) {
+                end = PAGING_MAX_PHYS;
+            }
+
+            // Region above PAGING_MAX_PHYS
+            if (base >= end) continue;
 
-    uint64_t page_count=0;
             for (uint64_t addr = base; addr < end; addr += PAGE_SIZE) {
                 pmm_free(addr);
-        page_count++;
+                total_pages++;
             }
-    DEBUG("%u frames in freelist, available for use (%u bytes)", page_count, page_count*PAGE_SIZE);
+        }
+    }
+
+    DEBUG("%u frames in freelist, %u bytes available (%u MB)", total_pages, total_pages*PAGE_SIZE, total_pages*PAGE_SIZE/1000000);
 }
 
 /*
@@ -124,9 +102,9 @@ static void pmm_init_freelist()
 void pmm_init(struct boot_context boot_ctx)
 {
     hhdm_off = boot_ctx.hhdm->offset;
-    pmm_find_biggest_usable_region(boot_ctx.mmap, boot_ctx.hhdm);
+    //pmm_find_biggest_usable_region(boot_ctx.mmap, boot_ctx.hhdm);
 
     // Now we have biggest USABLE region,
     // so to populate the free list we just iterate through it
-    pmm_init_freelist();
+    pmm_init_freelist(boot_ctx.mmap);
 }

src/mem/utils.c

@@ -7,8 +7,8 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <limine.h>
-#include "kernel.h"
+#include <kernel.h>
-#include "string/string.h"
+#include <string/string.h>
 
 // We won't be linked to standard library, but still need the basic mem* functions
 // so everything goes allright with the compiler

src/mem/vmm.c

@@ -0,0 +1,270 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Virtual memory manager
+ * @license GPL-3.0-only
+ */
+
+/*
+The VMM (virtual memory manager) will have two roles:
+- mapping pages
+- unmapping pages
+in a specified virtual space
+
+compared to the PMM which allocs/frees 4kb frames ("physical pages").
+*/
+
+#include "config.h"
+#include <mem/vmm.h>
+#include <mem/paging.h>
+#include <stddef.h>
+#include <mem/pmm.h>
+#include <kernel.h>
+
+extern uint64_t *kernel_pml4;
+
+/*
+ * vmm_switch_to - Switch to a different VMM context
+ * @ctx: VMM context to switch to
+ *
+ * This function makes the CPU switch to another
+ * virtual memory context, by using the PML4 address
+ * specified in the VMM context pointed to by @ctx.
+ */
+void vmm_switch_to(struct vmm_context* ctx)
+{
+    if (!ctx || !ctx->pml4) {
+        panic(NULL, "Attempted to switch to bad PML4!");
+    }
+    uint64_t pml4 = VIRT_TO_PHYS(ctx->pml4);
+    asm volatile ("mov %0, %%cr3" :: "r"(pml4) : "memory");
+}
+
+/*
+ * vmm_virt_to_phys - Translate from virtual to physical address
+ * @pml4: virtual address of the Page Map Level 4 (root page table)
+ * @virt: virtual address to translate
+ *
+ * This function goes through page table structures, beginning at
+ * the root page table which lives at @pml4, and translates @virt
+ * to a physical address, if it's found in the tables.
+ *
+ * Return:
+ * <phys> - physical address
+ * %-1     - address is not present in page tables pointed to by @pml4
+ */
+uint64_t vmm_virt_to_phys(uint64_t* pml4, uint64_t virt)
+{
+    uint64_t pml4_i = PML4_INDEX(virt);
+    uint64_t pdpt_i = PDPT_INDEX(virt);
+    uint64_t pd_i = PD_INDEX(virt);
+    uint64_t pt_i = PT_INDEX(virt);
+
+    if (!(pml4[pml4_i] & PTE_PRESENT)) return -1;
+    uint64_t* pdpt = (uint64_t*)PHYS_TO_VIRT(pml4[pml4_i] & PTE_ADDR_MASK);
+
+    if (!(pdpt[pdpt_i] & PTE_PRESENT)) return -1;
+    uint64_t* pd = (uint64_t*)PHYS_TO_VIRT(pdpt[pdpt_i] & PTE_ADDR_MASK);
+
+    if (!(pd[pd_i] & PTE_PRESENT)) return -1;
+    uint64_t* pt = (uint64_t*)PHYS_TO_VIRT(pd[pd_i] & PTE_ADDR_MASK);
+
+    if (!(pt[pt_i] & PTE_PRESENT)) return -1;
+
+    uint64_t phys = (pt[pt_i] & PTE_ADDR_MASK) + (virt & 0xFFF);
+    return phys;
+}
+
+/*
+ * vmm_create_address_space - Create a new address space
+ *
+ * This function allocates a PML4, and then copies the kernel
+ * page tables into it.
+ *
+ * Return:
+ * <pml4>  - address of the new PML4
+ * NULL    - on error (couldn't allocate a page table)
+ */
+uint64_t* vmm_create_address_space()
+{
+    uint64_t* pml4 = alloc_page_table();
+    if (!pml4) return NULL;
+
+    for (size_t i=256; i<512; i++) {
+        pml4[i] = kernel_pml4[i];
+    }
+
+    return pml4;
+}
+
+/*
+ * vmm_map - Map & allocate a page
+ * @pml4:  Page Map Level 4 (root table)
+ * @virt:  Virtual address to map
+ * @flags: Flags to apply on page
+ *
+ * This function allocates a page frame with the PMM,
+ * and maps this page to the provided @virt address,
+ * with the corresponding @flags.
+ *
+ * Return:
+ * <virt> - virtual address
+ */
+void* vmm_map(uint64_t* pml4, uint64_t virt, uint64_t flags)
+{
+    uint64_t phys = pmm_alloc();
+    if (!phys) {
+        panic(NULL, "VMM/PMM out of memory!");
+    }
+
+    paging_map_page(pml4, virt, phys, flags | PTE_PRESENT);
+    return (void*)virt;
+}
+
+/*
+ * vmm_unmap - Unmap & free a page
+ * @pml4:  Page Map Level 4 (root table)
+ * @virt:  Virtual address to unmap
+ *
+ * This function frees a page frame with the PMM,
+ * and unmaps the virtual page at @virt.
+ */
+void vmm_unmap(uint64_t* pml4, uint64_t virt)
+{
+    uint64_t pml4_i = PML4_INDEX(virt);
+    uint64_t pdpt_i = PDPT_INDEX(virt);
+    uint64_t pd_i   = PD_INDEX(virt);
+    uint64_t pt_i   = PT_INDEX(virt);
+
+    if (!(pml4[pml4_i] & PTE_PRESENT)) return;
+    uint64_t* pdpt = (uint64_t*)PHYS_TO_VIRT(pml4[pml4_i] & PTE_ADDR_MASK);
+
+    if (!(pdpt[pdpt_i] & PTE_PRESENT)) return;
+    uint64_t* pd = (uint64_t*)PHYS_TO_VIRT(pdpt[pdpt_i] & PTE_ADDR_MASK);
+
+    if (!(pd[pd_i] & PTE_PRESENT)) return;
+    uint64_t* pt = (uint64_t*)PHYS_TO_VIRT(pd[pd_i] & PTE_ADDR_MASK);
+
+    if (!(pt[pt_i] & PTE_PRESENT)) return;
+
+    uint64_t phys = pt[pt_i] & PTE_ADDR_MASK;
+    pmm_free(phys);
+
+    pt[pt_i] = 0;
+
+    invlpg((void*)virt);
+}
+
+/*
+ * vmm_is_mapped - Check if an address is mapped
+ * @pml4:  Page Map Level 4 (root table)
+ * @virt:  Virtual address to check
+ *
+ * This function checks if the @virt address is
+ * mapped in the tables pointed to by @pml4.
+ *
+ * Return:
+ * true  - @virt is mapped in tables of @pml4
+ * false - @virt is not mapped there
+ */
+bool vmm_is_mapped(uint64_t* pml4, uint64_t virt)
+{
+    uint64_t pml4_i = PML4_INDEX(virt);
+    uint64_t pdpt_i = PDPT_INDEX(virt);
+    uint64_t pd_i   = PD_INDEX(virt);
+    uint64_t pt_i   = PT_INDEX(virt);
+
+    if (!(pml4[pml4_i] & PTE_PRESENT)) return false;
+    uint64_t* pdpt = (uint64_t*)PHYS_TO_VIRT(pml4[pml4_i] & PTE_ADDR_MASK);
+
+    if (!(pdpt[pdpt_i] & PTE_PRESENT)) return false;
+    uint64_t* pd = (uint64_t*)PHYS_TO_VIRT(pdpt[pdpt_i] & PTE_ADDR_MASK);
+
+    if (!(pd[pd_i] & PTE_PRESENT)) return false;
+    uint64_t* pt = (uint64_t*)PHYS_TO_VIRT(pd[pd_i] & PTE_ADDR_MASK);
+
+    return (pt[pt_i] & PTE_PRESENT);
+}
+
+/*
+ * vmm_alloc_range - Map and allocate a memory range
+ * @pml4:  Page Map Level 4 (root table)
+ * @pages: Amount of pages to allocate/map
+ * @flags: Flags to put on mapped pages
+ *
+ * This function looks for enough space in page tables
+ * to map @pages pages, then maps them into the provided
+ * @pml4 with the provided @flags and allocates them.
+ *
+ * Return:
+ * <start_virt> - the starting virtual address for the mapped range
+ */
+void* vmm_alloc_region(uint64_t* pml4, size_t pages, uint64_t flags)
+{
+    uint64_t found_pages = 0;
+    uint64_t start_virt = VMM_USER_SPACE_START;
+
+    for (uint64_t curr = VMM_USER_SPACE_START; curr < VMM_USER_SPACE_END; curr += PAGE_SIZE) {
+        if (!vmm_is_mapped(pml4, curr)) {
+            if (found_pages == 0) start_virt = curr;
+            found_pages++;
+        } else {
+            found_pages = 0;
+        }
+
+        if (found_pages == pages) {
+            for (size_t i = 0; i < pages; i++) {
+                uint64_t addr_to_map = start_virt + (i * PAGE_SIZE);
+                if (!vmm_map(pml4, addr_to_map, flags)) {
+                    panic(NULL, "VMM out of memory!");
+                }
+            }
+            return (void*)start_virt;
+        }
+    }
+
+    panic(NULL, "VMM out of memory!");
+    return NULL;
+}
+
+/*
+ * vmm_map_user_stack - Map a user stack
+ * @pml4: the user process's PML4
+ *
+ * This function maps and allocates a userspace
+ * stack in the user @pml4 provided, according
+ * to constants USER_STACK_TOP and USER_STACK_PAGES.
+ *
+ * Return:
+ * <addr> - User stack top address
+ */
+
+uintptr_t vmm_alloc_user_stack(uint64_t* pml4)
+{
+    uintptr_t stack_top = USER_STACK_TOP;
+    size_t stack_size = USER_STACK_PAGES*PAGE_SIZE;
+
+    for (size_t i=stack_top; i>stack_top-stack_size; i-=PAGE_SIZE) {
+        vmm_map(pml4, i, PTE_PRESENT | PTE_WRITABLE | PTE_USER);
+    }
+    return stack_top;
+}
+
+uintptr_t vmm_alloc_user_code(uint64_t* pml4, void* code_addr, uint64_t code_size)
+{
+    uintptr_t code_start = USER_CODE_START;
+    
+    // Round code_size up to next page boundary
+    uint64_t code_size_aligned = (code_size + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
+    
+    for (uint64_t i=code_start; i<code_start+code_size_aligned; i+=PAGE_SIZE) {
+        vmm_map(pml4, i, PTE_PRESENT | PTE_WRITABLE | PTE_USER);
+    } 
+    
+    return code_start;
+}
+
+void vmm_init()
+{
+    // NO U
+    //vmm_setup_pt_root();
+}

src/sched/process.c

@@ -4,20 +4,23 @@
  * @license GPL-3.0-only
  */
 
+#include "mem/paging.h"
+#include "mem/vmm.h"
 #include <stddef.h>
-#include "process.h"
+#include <sched/process.h>
-#include "mem/heap/kheap.h"
+#include <mem/kheap.h>
-#include "kernel.h"
+#include <kernel.h>
-#include "string/string.h"
+#include <string/string.h>
-#include "mem/gdt/gdt.h"
+#include <arch/gdt.h>
-#include "config.h"
+#include <config.h>
-#include "io/serial/serial.h"
+#include <io/serial/serial.h>
+#include <io/term/flanterm.h>
+#include <mem/utils.h>
 
-#include "io/term/flanterm.h"
 extern struct flanterm_context* ft_ctx;
 
-struct process_t* processes_list;
+struct process* processes_list;
-struct process_t* current_process;
+struct process* current_process;
 
 extern uint64_t *kernel_pml4;
 
@@ -39,10 +42,10 @@ void process_init()
  * This function prints the linked list of processes
  * to the DEBUG output.
  */
-void process_display_list(struct process_t* processes_list)
+void process_display_list(struct process* processes_list)
 {
     int process_view_id = 0;
-    struct process_t* tmp = processes_list;
+    struct process* tmp = processes_list;
     while (tmp != NULL) {
         DEBUG("{%d: %p} -> ", process_view_id, tmp);
         tmp = tmp->next;
@@ -64,11 +67,11 @@ void process_display_list(struct process_t* processes_list)
  * Return:
  * <proc> - pointer to created process
  */
-struct process_t* process_create(char* name, void(*function)(void*), void* arg)
+struct process* process_create(char* name, void(*function)(void*), void* arg)
 {
     CLEAR_INTERRUPTS;
-    struct process_t* proc = (struct process_t*)kmalloc(sizeof(struct process_t));
+    struct process* proc = (struct process*)kmalloc(sizeof(struct process));
-    struct cpu_status_t* ctx = (struct cpu_status_t*)kmalloc(sizeof(struct cpu_status_t));
+    struct cpu_status* ctx = (struct cpu_status*)kmalloc(sizeof(struct cpu_status));
 
     // No more memory?
     if (!proc) return NULL;
@@ -95,6 +98,8 @@ struct process_t* process_create(char* name, void(*function)(void*), void* arg)
     // Kernel PML4 as it already maps code/stack (when switching to userland we'll have to change that)
     proc->root_page_table = kernel_pml4;
 
+    proc->kernel_stack = kalloc_stack();
+
     proc->next = 0;
 
     process_add(&processes_list, proc);
@@ -108,7 +113,7 @@ struct process_t* process_create(char* name, void(*function)(void*), void* arg)
  * @processes_list: pointer to the head of the linked list
  * @process:        process to add at the end of the linked list
  */
-void process_add(struct process_t** processes_list, struct process_t* process)
+void process_add(struct process** processes_list, struct process* process)
 {
     if (!process) return;
     process->next = NULL;
@@ -119,7 +124,7 @@ void process_add(struct process_t** processes_list, struct process_t* process)
         return;
     }
 
-    struct process_t* tmp = *processes_list;
+    struct process* tmp = *processes_list;
     while (tmp->next != NULL) {
         tmp = tmp->next;
     }
@@ -132,7 +137,7 @@ void process_add(struct process_t** processes_list, struct process_t* process)
  * @processes_list: pointer to head of linked list
  * @process:        the process to delete from the list
  */
-void process_delete(struct process_t** processes_list, struct process_t* process)
+void process_delete(struct process** processes_list, struct process* process)
 {
     if (!processes_list || !*processes_list || !process) return;
 
@@ -144,7 +149,7 @@ void process_delete(struct process_t** processes_list, struct process_t* process
         return;
     }
 
-    struct process_t* tmp = *processes_list;
+    struct process* tmp = *processes_list;
     while (tmp->next && tmp->next != process) {
         tmp = tmp->next;
     }
@@ -167,7 +172,7 @@ void process_delete(struct process_t** processes_list, struct process_t* process
  * Return:
  * <process->next> - process right after the one specified
  */
-struct process_t* process_get_next(struct process_t* process)
+struct process* process_get_next(struct process* process)
 {
     if (!process) return NULL;
     return process->next;
@@ -197,3 +202,97 @@ void process_exit()
         asm("hlt");
     }
 }
+
+/*
+ * process_jump_to_user - Jump to userland
+ * @stack_top: Address of the top of the user stack
+ * @user_code: Address of the first instruction of user code
+ */
+void process_jump_to_user(uintptr_t stack_top, uintptr_t user_code)
+{
+    // 0x20 | 3 = 0x23 (user data segment | 3)
+    // 0x18 | 3 = 0x1B (user code segment | 3)
+    asm volatile(" \
+        push $0x23 \n\
+        push %0 \n\
+        push $0x202 \n\
+        push $0x1B \n\
+        push %1 \n\
+        iretq \n\
+        " :: "r"(stack_top), "r"(user_code));
+}
+
+extern struct tss tss;
+
+/*
+ * process_create_user_raw - Create a new user process from raw binary
+ * @file: pointer to beginning of binary
+ * @size: size of the binary
+ * @name: name for the new process
+ *
+ * This function takes an executable loaded in memory
+ * and maps its code, a user stack, sets the TSS RSP0
+ * for interrupts, and finally jumps to the user code.
+ */
+void process_create_user_raw(char* file, int size, char* name)
+{
+    CLEAR_INTERRUPTS;
+    struct process* proc = (struct process*)kmalloc(sizeof(struct process));
+    struct cpu_status* ctx = (struct cpu_status*)kmalloc(sizeof(struct cpu_status));
+
+    if (!proc || !ctx) panic(NULL, "out of memory while creating user process");
+
+    memset(proc, 0, sizeof(struct process));
+    memset(ctx, 0, sizeof(struct cpu_status));
+
+    strncpy(proc->name, name, PROCESS_NAME_MAX);
+    proc->pid = next_free_pid++;
+    proc->status = READY;
+    proc->next = 0;
+    proc->context = ctx;
+    proc->context->iret_ss = USER_DATA_SEGMENT | 3;
+    proc->context->iret_cs = USER_CODE_SEGMENT | 3;
+    proc->context->iret_flags = 0x202; // Interrupt Flag set
+
+        /* Set basic entries for the process's File Descriptor Table */
+    proc->fdt[0].fd = 0;
+    proc->fdt[0].open = true;
+    proc->fdt[0].cursor = 0;
+    strncpy(proc->fdt[0].filename, "stdin", PROCESS_NAME_MAX - 1);
+
+    proc->fdt[1].fd = 1;
+    proc->fdt[1].open = true;
+    proc->fdt[1].cursor = 0;
+    strncpy(proc->fdt[1].filename, "stdout", PROCESS_NAME_MAX - 1);
+
+    proc->fdt[2].fd = 2;
+    proc->fdt[2].open = true;
+    proc->fdt[2].cursor = 0;
+    strncpy(proc->fdt[2].filename, "stderr", PROCESS_NAME_MAX - 1);
+
+    proc->next_free_fd = 3; // file descriptors are also bump-allocated
+
+    void* exec_addr = (void*)file;
+    uint64_t exec_size = size;
+
+    uint64_t* user_pml4 = vmm_create_address_space();
+    if (!user_pml4) panic(NULL, "failed to create user address space");
+    proc->root_page_table = user_pml4;
+
+    uintptr_t stack_top = vmm_alloc_user_stack(user_pml4);
+    uint64_t code = vmm_alloc_user_code(user_pml4, exec_addr, exec_size);
+    
+    proc->context->iret_rsp = stack_top;
+    proc->context->iret_rip = code;
+    proc->kernel_stack = kalloc_stack();
+    if (!proc->kernel_stack) panic(NULL, "failed to allocate kernel stack");
+
+    // Copy code into user pages; for that we need to temporarily switch to the user pml4
+    load_cr3(VIRT_TO_PHYS((uint64_t)user_pml4));
+    memcpy((uint64_t*)code, exec_addr, exec_size);
+    load_cr3(VIRT_TO_PHYS((uint64_t)kernel_pml4));
+
+    process_add(&processes_list, proc);
+    DEBUG("user process '%s' (pid=%u) enqueued for scheduling", name, proc->pid);
+    SET_INTERRUPTS;
+}

src/sched/process.h

@@ -1,39 +0,0 @@
-/*
- * @author  xamidev <xamidev@riseup.net>
- * @brief   Process definition
- * @license GPL-3.0-only
- */
-
-#ifndef PROCESS_H
-#define PROCESS_H
-
-#include <stddef.h>
-#include "config.h"
-#include <stdint.h>
-
-typedef enum {
-    READY,
-    RUNNING,
-    DEAD
-} status_t;
-
-struct process_t {
-    size_t pid;
-    char name[PROCESS_NAME_MAX];
-
-    status_t status;
-    struct cpu_status_t* context;
-	void* root_page_table; // Process PML4 (should contain kernel PML4 in higher half [256-511]
-    struct process_t* next;
-};
-
-void process_init(void);
-struct process_t* process_create(char* name, void(*function)(void*), void* arg);
-void process_add(struct process_t** processes_list, struct process_t* process);
-void process_delete(struct process_t** processes_list, struct process_t* process);
-struct process_t* process_get_next(struct process_t* process);
-void process_exit(void);
-
-void process_display_list(struct process_t* processes_list);
-
-#endif

src/sched/scheduler.c

@@ -4,15 +4,18 @@
  * @license GPL-3.0-only
  */
 
-#include "kernel.h"
+#include <kernel.h>
-#include "process.h"
+#include <sched/process.h>
-#include "mem/paging/paging.h"
+#include <mem/paging.h>
 #include <stdint.h>
-#include "io/serial/serial.h"
+#include <io/serial/serial.h>
+#include <arch/gdt.h>
 
-extern struct process_t* processes_list;
+extern struct process* processes_list;
-extern struct process_t* current_process;
+extern struct process* current_process;
-extern struct process_t* idle_proc;
+extern struct process* idle_proc;
+
+extern struct tss tss;
 
 /*
  * scheduler_init - Choose the first process
@@ -20,6 +23,7 @@ extern struct process_t* idle_proc;
 void scheduler_init()
 {
     current_process = processes_list;
+    DEBUG("scheduler starting with: pid=%u, name='%s', context=%p", current_process->pid, current_process->name, current_process->context);
 }
 
 /*
@@ -32,47 +36,63 @@ void scheduler_init()
  * Return:
  * <context> - CPU context for next process
  */
-struct cpu_status_t* scheduler_schedule(struct cpu_status_t* context)
+struct cpu_status* scheduler_schedule(struct cpu_status* context)
 {
     if (context == NULL) {
         panic(NULL, "Scheduler called with NULL context"); 
     }
 
     if (current_process == NULL) {
-        // If no more processes, then set IDLE as the current process, that's it.
+        panic(NULL, "current_process is NULL");
-        current_process = idle_proc;
     }
     
-    if (current_process == idle_proc && current_process->next == NULL)
+    if (current_process->context == NULL) {
-    {
+        panic(NULL, "current_process->context is NULL");
-        return idle_proc->context;
     }
 
     current_process->context = context;
-    //current_process->status = READY;
 
-    for (;;) {
+    if (current_process->status == DEAD) {
-        struct process_t* prev_process = current_process;
+        struct process* dead_process = current_process;
-        if (current_process->next != NULL) {
+        struct process* next_process = (dead_process->next != NULL) ? dead_process->next : processes_list;
+
+        process_delete(&processes_list, dead_process);
+
+        if (processes_list == NULL || next_process == dead_process) {
+            current_process = idle_proc;
+            return idle_proc->context;
+        }
+
+        current_process = next_process;
+    } else if (current_process->next != NULL) {
         current_process = current_process->next;
     } else {
         current_process = processes_list;
     }
 
-        if (current_process != NULL && current_process->status == DEAD) {
+    for (;;) {
-            process_delete(&prev_process, current_process);
+        if (current_process->status == DEAD) {
-            current_process = NULL;
+            struct process* dead_process = current_process;
+            struct process* next_process = (current_process->next != NULL) ? current_process->next : processes_list;
+
+            process_delete(&processes_list, dead_process);
+
+            if (processes_list == NULL || next_process == dead_process) {
+                current_process = idle_proc;
                 return idle_proc->context;
-        } else {
+            }
+
+            current_process = next_process;
+            continue;
+        }
+
         current_process->status = RUNNING;
         break;
     }
-    }
-
-    DEBUG("current_process={pid=%u, name='%s', root_page_table[virt]=%p}", current_process->pid, current_process->name, current_process->root_page_table);
 
+    // Here, we chose next running process so we load its kernel stack & page tables
+    tss.rsp0 = (uint64_t)current_process->kernel_stack;
     load_cr3(VIRT_TO_PHYS((uint64_t)current_process->root_page_table));
-    DEBUG("Loaded process PML4 into CR3");
 
     return current_process->context;
 }

src/sched/spinlock.c

@@ -0,0 +1,44 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Spinlock implementation
+ * @license GPL-3.0-only
+ */
+
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <kernel.h>
+#include <sched/spinlock.h>
+
+/*
+ * spinlock_acquire - Lock a lock
+ * @lock: pointer to desired spinlock
+ *
+ * Saves the RFLAGS register, then acquires a lock.
+ * Pause instruction is used to ease the CPU.
+ */
+void spinlock_acquire(struct spinlock* lock)
+{
+    uint64_t rflags;
+    asm volatile("pushfq ; pop %0 ; cli" : "=rm"(rflags) : : "memory");
+
+    while (__atomic_test_and_set(&lock->locked, __ATOMIC_ACQUIRE)) {
+        __builtin_ia32_pause();
+    }
+
+    lock->rflags = rflags;
+}
+
+/*
+ * spinlock_release - Unlock a lock
+ * @lock: pointer to desired spinlock
+ *
+ * Gets saved RFLAGS register from the lock and
+ * unlocks it (clears locked state).
+ * RFLAGS is then restored.
+ */
+void spinlock_release(struct spinlock* lock)
+{
+    uint64_t rflags = lock->rflags;
+    __atomic_clear(&lock->locked, __ATOMIC_RELEASE);
+    asm volatile("push %0 ; popfq" : : "rm"(rflags) : "memory");
+}

src/security/ssp.c

@@ -0,0 +1,17 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Stack Smashing Protection feature
+ * @license GPL-3.0-only
+ */
+
+#include <config.h>
+#include <stdint.h>
+#include <kernel.h>
+#include <stddef.h>
+
+uint64_t __stack_chk_guard = STACK_CHK_GUARD;
+
+void __stack_chk_fail(void)
+{
+	panic(NULL, "SSP: Stask Smashing Detected!!! (very spicy)");
+}

src/security/ubsan.c

@@ -0,0 +1,293 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Undefined behavior sanitization hooks
+ * @license GPL-3.0-only
+ */
+
+#include <stdint.h>
+#include <security/ubsan.h>
+#include <kernel.h>
+#include <stddef.h>
+
+/*
+ * Hooks were inspired from the Sortix implementation:
+ * https://gitlab.com/sortix/sortix/-/blob/main/libc/ubsan/ubsan.c
+ *
+ * Not all hooks are implemented here.
+ */
+
+extern struct init_status init;
+
+/*
+ * __ubsan_handle_type_mismatch_v1 - Hook for UBSan
+ * @data_raw:    pointer to error data
+ * @pointer_raw: faulty pointer
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: type mismatch, null pointer
+ * access, and unaligned access. It halts the system and
+ * gives the location of the code that triggered it.
+ */
+void __ubsan_handle_type_mismatch_v1(void* data_raw, void* pointer_raw)
+{
+	struct ubsan_type_mismatch_v1_data* data = (struct ubsan_type_mismatch_v1_data*) data_raw;
+	uintptr_t pointer = (uintptr_t)pointer_raw;
+	uintptr_t alignment = (uintptr_t)1UL << data->log_alignment;
+	const char* violation = "type mismatch";
+	if ( !pointer ) {
+        violation = "null pointer access";
+    }
+	else if ( alignment && (pointer & (alignment - 1)) ) {
+        violation = "unaligned access";
+    }
+	
+    struct ubsan_source_location* loc = &data->location;
+
+    DEBUG("\x1b[38;5;231mUBSan: %s (ptr=%p) at %s:%u:%u\x1b[0m", violation, pointer, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: %s (ptr=%p) at %s:%u:%u\x1b[0m\r\n", violation, pointer, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error");
+}
+
+/*
+ * __ubsan_handle_pointer_overflow - Hook for UBSan
+ * @data_raw:   pointer to error data
+ * @base_raw:   base pointer
+ * @result_raw: pointer after faulty operation
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: pointer overflow.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_pointer_overflow(void* data_raw, void* base_raw, void* result_raw)
+{
+	struct ubsan_pointer_overflow_data* data = (struct ubsan_pointer_overflow_data*) data_raw;
+	uintptr_t base = (uintptr_t)base_raw;
+	uintptr_t result = (uintptr_t)result_raw;
+    
+    struct ubsan_source_location* loc = &data->location;
+
+    DEBUG("\x1b[38;5;231mUBSan: pointer overflow (base=%p, result=%p) at %s:%u:%u\x1b[0m", base, result, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: pointer overflow (base=%p, result=%p) at %s:%u:%u\x1b[0m", base, result, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: pointer overflow");
+}
+
+/*
+ * __ubsan_handle_shift_out_of_bounds - Hook for UBSan
+ * @data_raw: pointer to error data
+ * @lhs_raw:  left hand side (value being shifted)
+ * @rhs_raw:  right hand side (shift amount)
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: shift out of bounds.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_shift_out_of_bounds(void* data_raw, void* lhs_raw, void* rhs_raw)
+{
+	struct ubsan_shift_out_of_bounds_data* data = (struct ubsan_shift_out_of_bounds_data*) data_raw;
+	uintptr_t lhs = (uintptr_t) lhs_raw;
+	uintptr_t rhs = (uintptr_t) rhs_raw;
+	
+    struct ubsan_source_location* loc = &data->location;
+
+    DEBUG("\x1b[38;5;231mUBSan: shift out of bounds (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: shift out of bounds (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: shift out of bounds");
+}
+
+/*
+ * __ubsan_handle_load_invalid_value - Hook for UBSan
+ * @data_raw:    pointer to error data
+ * @value_raw:   value loaded
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: invalid value load.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_load_invalid_value(void* data_raw, void* value_raw)
+{
+	struct ubsan_invalid_value_data* data = (struct ubsan_invalid_value_data*) data_raw;
+	uintptr_t value = (uintptr_t) value_raw;
+
+    struct ubsan_source_location* loc = &data->location;
+
+    DEBUG("\x1b[38;5;231mUBSan: invalid value load (value=%p) at %s:%u:%u\x1b[0m", value, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: invalid value load (value=%p) at %s:%u:%u\x1b[0m", value, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: invalid value load");
+}
+
+/*
+ * __ubsan_handle_out_of_bounds - Hook for UBSan
+ * @data_raw:    pointer to error data
+ * @index_raw:   out-of-bounds index in array
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: access out of bounds.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_out_of_bounds(void* data_raw, void* index_raw)
+{
+	struct ubsan_out_of_bounds_data* data = (struct ubsan_out_of_bounds_data*) data_raw;
+	uintptr_t index = (uintptr_t) index_raw;
+    struct ubsan_source_location* loc = &data->location;
+
+    DEBUG("\x1b[38;5;231mUBSan: out of bounds (index=%p) at %s:%u:%u\x1b[0m", index, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: out of bounds (index=%p) at %s:%u:%u\x1b[0m", index, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: out of bounds");
+}
+
+/*
+ * __ubsan_handle_divrem_overflow - Hook for UBSan
+ * @data_raw:    pointer to error data
+ * @lhs_raw:     left hand side operator
+ * @rhs_raw:     right hand side operator
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: division remainder overflow.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_divrem_overflow(void* data_raw, void* lhs_raw, void* rhs_raw)
+{
+	struct ubsan_overflow_data* data = (struct ubsan_overflow_data*) data_raw;
+	uintptr_t lhs = (uintptr_t) lhs_raw;
+	uintptr_t rhs = (uintptr_t) rhs_raw;
+    struct ubsan_source_location* loc = &data->location;
+
+	DEBUG("\x1b[38;5;231mUBSan: division remainder overflow (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: division remainder overflow (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: division remainder overflow");
+}
+
+/*
+ * __ubsan_handle_sub_overflow - Hook for UBSan
+ * @data_raw:    pointer to error data
+ * @lhs_raw:     left hand side operator
+ * @rhs_raw:     right hand side operator
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: subtraction overflow.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_sub_overflow(void* data_raw, void* lhs_raw, void* rhs_raw)
+{
+	struct ubsan_overflow_data* data = (struct ubsan_overflow_data*) data_raw;
+	uintptr_t lhs = (uintptr_t) lhs_raw;
+	uintptr_t rhs = (uintptr_t) rhs_raw;
+	struct ubsan_source_location* loc = &data->location;
+
+	DEBUG("\x1b[38;5;231mUBSan: subtraction overflow (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: subtraction overflow (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: subtraction overflow");
+}
+
+/*
+ * __ubsan_handle_add_overflow - Hook for UBSan
+ * @data_raw:    pointer to error data
+ * @lhs_raw:     left hand side operator
+ * @rhs_raw:     right hand side operator
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: addition overflow.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_add_overflow(void* data_raw, void* lhs_raw, void* rhs_raw)
+{
+	struct ubsan_overflow_data* data = (struct ubsan_overflow_data*) data_raw;
+	uintptr_t lhs = (uintptr_t) lhs_raw;
+	uintptr_t rhs = (uintptr_t) rhs_raw;
+    struct ubsan_source_location* loc = &data->location;
+
+	DEBUG("\x1b[38;5;231mUBSan: addition overflow (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: addition overflow (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: addition overflow");
+}
+
+/*
+ * __ubsan_handle_mul_overflow - Hook for UBSan
+ * @data_raw:    pointer to error data
+ * @lhs_raw:     left hand side operator
+ * @rhs_raw:     right hand side operator
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: multiplication overflow.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_mul_overflow(void* data_raw, void* lhs_raw, void* rhs_raw)
+{
+	struct ubsan_overflow_data* data = (struct ubsan_overflow_data*) data_raw;
+	uintptr_t lhs = (uintptr_t) lhs_raw;
+	uintptr_t rhs = (uintptr_t) rhs_raw;
+	struct ubsan_source_location* loc = &data->location;
+
+	DEBUG("\x1b[38;5;231mUBSan: multiplication overflow (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: multiplication overflow (lhs=%p, rhs=%p) at %s:%u:%u\x1b[0m", lhs, rhs, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: multiplication overflow");
+}
+
+/*
+ * __ubsan_handle_negate_overflow - Hook for UBSan
+ * @data_raw:      pointer to error data
+ * @old_value_raw: value before overflow
+ *
+ * This function is executed when the UBSan library detects
+ * following undefined behavior: negation overflow.
+ * It halts the system and gives the location of the code
+ * that triggered it.
+ */
+void __ubsan_handle_negate_overflow(void* data_raw, void* old_value_raw)
+{
+	struct ubsan_overflow_data* data = (struct ubsan_overflow_data*) data_raw;
+	uintptr_t old_value = (uintptr_t) old_value_raw;
+    struct ubsan_source_location* loc = &data->location;
+
+	DEBUG("\x1b[38;5;231mUBSan: negation overflow (old_value=%p) at %s:%u:%u\x1b[0m", old_value, loc->filename, loc->line, loc->column);
+
+    if (init.all) {
+        printf("\x1b[38;5;231mUBSan: negation overflow (old_value=%p) at %s:%u:%u\x1b[0m", old_value, loc->filename, loc->line, loc->column);
+    }
+
+    panic(NULL, "Undefined Behavior Sanitization error: negation overflow");
+}

src/string/string.c

@@ -70,3 +70,40 @@ void strncpy(char* dst, const char* src, size_t n)
    size_t i = 0;
    while(i++ != n && (*dst++ = *src++));
 }
+
+
+/*
+ * strncmp - compare two strings up to n characters
+ * @s1: first string
+ * @s2: second string
+ * @n:  number of bytes to compare
+ *
+ * Taken from: https://github.com/DevSolar/pdclib/blob/master/functions/string/strncmp.c
+ *
+ * Return:
+ * $0  - @s1 and @s2 are equal
+ * $<0 - @s1 is less than @s2
+ * $>0 - @s1 is greater than @s2 
+ */
+int strncmp(const char* s1, const char* s2, size_t n)
+{
+    while ( n && *s1 && ( *s1 == *s2 ) ) {
+        ++s1;
+        ++s2;
+        --n;
+    }
+    if ( n == 0 ) {
+        return 0;
+    }
+    else {
+        return ( *(unsigned char *)s1 - *(unsigned char *)s2 );
+    }
+}
+
+// BSD implementation
+size_t strlen(const char* str)
+{
+        const char* s;
+        for (s = str; *s; ++s);
+        return (s - str);
+}

src/time/date.c

@@ -0,0 +1,89 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   Date helper functions
+ * @license GPL-3.0-only
+ */
+
+#include <stdint.h>
+#include <time/date.h>
+#include <mem/utils.h>
+#include <kernel.h>
+
+extern struct boot_context boot_ctx;
+
+// Unix epoch used as reference: Jan 1st 1970, 00:00:00 UTC
+struct date epoch = {
+    .year = 1970,
+    .month = 1,
+    .day = 1,
+    .hour = 0,
+    .minute = 0,
+    .second = 0
+};
+
+/*
+ * date_timestamp_to_date - Convert UNIX timestamp to a date structure
+ * @timestamp: UNIX timestamp
+ * 
+ * Return:
+ * <date> - date structure
+ */
+struct date date_timestamp_to_date(uint64_t timestamp)
+{
+    struct date result;
+    memcpy(&result, &epoch, sizeof(struct date));
+    uint64_t nr_days = timestamp / 86400;
+
+    while (nr_days > 0) {
+        unsigned int nr_month = 0;
+        int leap_year = 0;
+
+        if (result.year % 4 == 0 && (result.year % 100 != 0 || result.year % 400 == 0)) {
+            leap_year = 1;
+        } else {
+            leap_year = 0;
+        }
+
+        if (result.month == 2) {
+            if (leap_year != 0) {
+                nr_month = 29;
+            } else {
+                nr_month = 28;
+            }
+        } else {
+            nr_month = 31 - ((result.month -1) % 7 % 2);
+        }
+        
+        if (nr_days >= nr_month) {
+            nr_days -= nr_month;
+            result.month++;
+            if (result.month > 12) {
+                result.month = 1;
+                result.year++;
+            }
+        } else {
+            result.day += nr_days;
+            nr_days = 0;
+        }
+    }
+
+    result.second = timestamp % 60;
+    timestamp /= 60;
+    result.minute = timestamp % 60;
+    timestamp /= 60;
+    result.hour = timestamp % 24;
+
+    return result;
+}
+
+/*
+ * date_now - Get the current date (time at boot + timer ticks)
+ *
+ * Return:
+ * <date> - date structure
+ */
+struct date date_now()
+{
+    uint64_t timestamp_now = boot_ctx.bootdate->boot_time + (ticks/1000);
+    return date_timestamp_to_date(timestamp_now);
+}

src/time/timer.c

@@ -5,9 +5,9 @@
  */
 
 #include <stdint.h>
-#include "io/serial/serial.h"
+#include <io/serial/serial.h>
 #include <kernel.h>
-#include "config.h"
+#include <config.h>
 
 /*
 For now, the timer module will be using the PIC.

user/Makefile

@@ -0,0 +1,18 @@
+CC := x86_64-elf-gcc
+CC_FLAGS := -ffreestanding -nostdlib -fno-pic -mno-red-zone -Ilibc
+
+LD := x86_64-elf-ld
+
+BUILDDIR := ../build
+LIBDIR := libc
+
+all: pedicel apex
+
+pedicel:
+	nasm -f bin pedicel.S -o $(BUILDDIR)/pedicel.raw
+
+apex:
+	$(CC) $(CC_FLAGS) -c apex.c -o $(BUILDDIR)/apex.o
+	nasm -f elf64 $(LIBDIR)/crt0.S -o $(BUILDDIR)/crt0.o
+	$(LD) -T $(LIBDIR)/linker.ld $(BUILDDIR)/crt0.o $(BUILDDIR)/apex.o -o $(BUILDDIR)/apex.elf
+	objcopy -O binary $(BUILDDIR)/apex.elf $(BUILDDIR)/apex.raw

user/apex.c

@@ -0,0 +1,7 @@
+#include <syscall.h>
+
+int main() {
+    const char* msg = "hi from C userland\r\n";
+    write(1, msg, 21);
+    return 42;
+}

user/libc/crt0.S

@@ -0,0 +1,18 @@
+bits 64
+global _start
+extern main
+
+section .text
+
+; Begin the program with main() function
+_start:
+    call main
+
+; Exit the program by exit() syscall
+.exit:
+    mov rdi, rax    ; put the value of "return X;" (rax) as arg1 (error_code)
+    mov rax, 60     ; sys_exit
+    int 0x80
+
+.loop:
+    jmp .loop

user/libc/linker.ld

@@ -0,0 +1,22 @@
+ENTRY(_start)
+
+SECTIONS
+{
+    . = 0x400000;
+
+    .text : {
+        *(.text*)
+    }
+
+    .rodata : {
+        *(.rodata*)
+    }
+
+    .data : {
+        *(.data*)
+    }
+
+    .bss : {
+        *(.bss*)
+    }
+}

user/libc/syscall.h

@@ -0,0 +1,30 @@
+#pragma once
+
+// 3 because 3 arguments to the call, get it??
+static inline long syscall3(long n, long a, long b, long c) {
+    long ret;
+
+    __asm__ volatile (
+        "int $0x80"
+        : "=a"(ret)
+        : "a"(n), "D"(a), "S"(b), "d"(c)
+        : "memory"
+    );
+
+    return ret;
+}
+
+static inline void write(int fd, const char* buf, long len) {
+    syscall3(1, fd, (long)buf, len);
+}
+
+static inline void exit(int code) {
+    __asm__ volatile (
+        "int $0x80"
+        :
+        : "a"(60), "D"(code)
+        : "memory"
+    );
+
+    for (;;);
+}

user/pedicel.S

@@ -0,0 +1,51 @@
+bits 64
+
+section .data
+hello db 0x0A, 0x0D, "TEST PROGRAM...", 0x0A, 0x0D, 0
+filename db "wow.txt", 0
+
+section .text
+
+_start:
+    mov rax, 0x1    ;sys_write
+    mov rdi, 0x1    ;stdout
+    lea rsi, [rel hello]
+    mov rdx, 19     ;count
+    int 0x80
+
+    ; Open a file
+    mov rax, 0x2            ;sys_open
+    lea rdi, [rel filename] ;filename
+    mov rsi, 0x0            ;flags
+    int 0x80
+
+    mov rdi, rax            ;fd
+    mov rax, 0x0            ;sys_read
+    lea rsi, [rel buf]      ;buf
+    mov rdx, 33             ;count
+    int 0x80
+
+    mov rax, 0x1        ;sys_write
+    mov rdi, 0x1        ;stdout
+    lea rsi, [rel buf]  ;buf
+    mov rdx, 33         ;count
+    int 0x80
+
+    mov rax, 0x3        ;sys_close
+    mov rdi, 0x3        ;fd
+    int 0x80
+
+; when we are ready to have an os specific toolchain,
+; this bit (exit & loop) should be appended at the end of every
+; C program we compile.
+
+.end:
+    mov rax, 0x3C
+    mov rdi, 0x0
+    int 0x80
+
+.loop:
+    jmp .loop
+
+section .bss
+buf resb 10

user/wow.txt

@@ -0,0 +1 @@
+hi from a file opened in usermode