Makefile

@@ -21,6 +21,7 @@ CC_FLAGS=-Wall -Wextra -std=gnu99 -nostdlib -ffreestanding -fstack-protector -fn
 LD := x86_64-elf-ld
 
 $(ELFFILE): $(BUILDDIR) $(OBJFILES)
+	nasm -f bin user/hello.S -o $(BUILDDIR)/hello
 	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
@@ -47,6 +48,7 @@ build-iso: limine/limine $(ELFFILE)
 	cp -v $(ELFFILE) iso_root/boot
 	mkdir -p iso_root/boot/limine
 	cp -v limine.conf iso_root/boot/limine
+	cp $(BUILDDIR)/hello 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/

include/config.h

@@ -40,6 +40,10 @@
 #define KERNEL_STACK_SIZE 65536
 #define KERNEL_IDT_ENTRIES 33
 
+/* user */
+#define USER_STACK_TOP 0x80000000
+#define USER_STACK_PAGES 16 // 16*4096 = 64kb
+
 /* paging */
 #define PAGING_MAX_PHYS 0x200000000
 

include/kernel.h

@@ -54,6 +54,7 @@ struct boot_context {
 	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?

include/sched/process.h

@@ -24,6 +24,7 @@ struct process {
     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 process* next;
 };
 

limine.conf

@@ -6,3 +6,4 @@ interface_branding: Welcome to the PepperOS disk!
 	
 	comment: Default configuration (warning: spicy)
 	path: boot():/boot/pepperk
+	module_path: boot():/boot/hello

src/boot/boot.c

@@ -13,6 +13,9 @@
 #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 = {
 	.id = LIMINE_FRAMEBUFFER_REQUEST,
@@ -43,8 +46,11 @@ volatile struct limine_boot_time_request date_request = {
 	.revision = 0
 };
 
-__attribute__((used, section(".limine_requests_start")))
+__attribute__((used, section(".limine_requests")))
-volatile LIMINE_REQUESTS_START_MARKER;
+volatile struct limine_module_request module_request = {
+	.id = LIMINE_MODULE_REQUEST,
+	.revision = 0
+};
 
 __attribute__((used, section(".limine_requests_end")))
 volatile LIMINE_REQUESTS_END_MARKER;
@@ -58,4 +64,5 @@ void populate_boot_context(struct boot_context* ctx)
 	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/debug/panic.c

@@ -18,7 +18,7 @@ extern int panic_count;
  */
 void read_rflags(uint64_t rflags)
 {
-	DEBUG("\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",
+	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*/

src/kmain.c

@@ -62,6 +62,9 @@ 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;
+
+struct limine_file* file;
 
 extern struct process* processes_list;
 extern struct process* current_process;
@@ -119,6 +122,15 @@ void kmain()
 
 	scheduler_init();
 
+	if (!boot_ctx.module) {
+		panic(NULL, "could not load 'hello' executable :(");
+	}
+
+	if (boot_ctx.module->module_count == 1) {
+		file = boot_ctx.module->modules[0];
+		DEBUG("file: addr=%p size=%u", file->address, file->size);
+	}
+
 	printf(PEPPEROS_SPLASH);
 	init.all = true;
 

src/mem/vmm.c

@@ -13,6 +13,7 @@ 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>
@@ -225,6 +226,30 @@ void* vmm_alloc_region(uint64_t* pml4, size_t pages, uint64_t flags)
     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;
+}
+
 void vmm_init()
 {
     // NO U

user/hello.S

@@ -0,0 +1,5 @@
+bits 64
+
+hello:
+    mov qword rax, 0xcafebabe
+    jmp hello