Scheduler fix, User RR

Makefile

@@ -16,12 +16,13 @@ endif
 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
+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 bin user/hello.S -o $(BUILDDIR)/hello
+	nasm -f bin user/pedicel.S -o $(BUILDDIR)/pedicel
 	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
@@ -49,6 +50,7 @@ build-iso: limine/limine $(ELFFILE)
 	mkdir -p iso_root/boot/limine
 	cp -v limine.conf iso_root/boot/limine
 	cp $(BUILDDIR)/hello iso_root/boot/
+	cp $(BUILDDIR)/pedicel 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/sched/process.h

@@ -38,6 +38,6 @@ void process_exit(void);
 
 void process_display_list(struct process* processes_list);
 
-void process_create_user(struct limine_file* file);
+void process_create_user(struct limine_file* file, char* name);
 
 #endif

limine.conf

@@ -7,3 +7,4 @@ interface_branding: Welcome to the PepperOS disk!
 	comment: Default configuration (warning: spicy)
 	path: boot():/boot/pepperk
 	module_path: boot():/boot/hello
+	module_path: boot():/boot/pedicel

src/arch/x86/idt.c

@@ -264,10 +264,9 @@ struct cpu_status* interrupt_dispatch(struct cpu_status* context)
             // Send an EOI so that we can continue having interrupts
             outb(0x20, 0x20);
 
-            // Scheduler is temporarily disabled to test user trampoline
+            if (ticks % SCHEDULER_QUANTUM == 0) {
-            /* if (ticks % SCHEDULER_QUANTUM == 0) {
                 return scheduler_schedule(context);
-            } */
+            }
 
             break;
 

src/arch/x86/syscall.c

@@ -9,6 +9,9 @@
 #include <kernel.h>
 #include <stddef.h>
 #include <io/term/term.h>
+#include <sched/process.h>
+
+extern struct process* current_process;
 
 void sys_write(unsigned int fd, const char* buf, size_t count)
 {
@@ -20,10 +23,19 @@ void sys_write(unsigned int fd, const char* buf, size_t count)
             break;
 
         case 2: //stderr
+            for (size_t i=0; i<count; i++) {
+                internal_putc(buf[i], NULL);
+            }
             break;
     }
 }
 
+void sys_exit(int error_code)
+{
+    current_process->status = DEAD;
+    DEBUG("exiting process PID=%u name=%s", current_process->pid, current_process->name);
+}
+
 /*
  * syscall_handler - System call dispatcher
  * @regs: CPU state
@@ -53,6 +65,9 @@ struct cpu_status* syscall_handler(struct cpu_status* regs)
         case 1: //sys_write
             sys_write(regs->rdi, (char*)regs->rsi, regs->rdx);
             break;
+        case 60: //sys_exit
+            sys_exit(regs->rdi);
+            break;
         default:
             regs->rax = 0xbad515ca11;
             break;

src/kmain.c

@@ -118,22 +118,22 @@ void kmain()
 	
 	process_init();
 	idle_proc = process_create("idle", (void*)idle_main, 0);
-	process_create("pedicel", (void*)pedicel_main, 0);
-
-	scheduler_init();
 
 	if (!boot_ctx.module) {
 		panic(NULL, "could not load 'hello' executable :(");
-	} 
+	}
+	if (boot_ctx.module->module_count == 2) {
+		file = boot_ctx.module->modules[0];
+		DEBUG("file: addr=%p size=%u", file->address, file->size);
+		process_create_user(file, "hello");
+
+		file = boot_ctx.module->modules[1];
+		process_create_user(file, "pedicel");
+	}
+	scheduler_init();
 
 	printf(PEPPEROS_SPLASH);
 	init.all = true;
 
-	if (boot_ctx.module->module_count == 1) {
-		file = boot_ctx.module->modules[0];
-		DEBUG("file: addr=%p size=%u", file->address, file->size);
-		process_create_user(file);
-	}
-
 	idle();
 }

src/mem/vmm.c

@@ -246,17 +246,19 @@ uintptr_t vmm_alloc_user_stack(uint64_t* pml4)
     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;
-
+    
-    for (size_t i=code_start; i<code_start+code_size; i+=PAGE_SIZE) {
+    // 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;
 }

src/sched/process.c

@@ -98,6 +98,8 @@ struct process* 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);
@@ -229,29 +231,52 @@ extern struct tss tss;
 /*
  * process_create_user - Create a new user process
  * @file: pointer to Limine file structure
+ * @name: name for the new process
  *
  * This function takes a loaded Limine executable
  * module, and maps its code, a user stack, sets the
  * TSS RSP0 for interrupts, and finally jumps to the
  * user code.
  */
-void process_create_user(struct limine_file* file)
+void process_create_user(struct limine_file* file, 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");
+
+    strncpy(proc->name, name, PROCESS_NAME_MAX);
+    memset(ctx, 0, sizeof(struct cpu_status)); // set GP registers to zero
+    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
+
     void* exec_addr = file->address;
     uint64_t exec_size = file->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);
     
-    // Could be kalloc_stack()ed PER PROCESS when we grow that
+    proc->context->iret_rsp = stack_top;
-    tss.rsp0 = (uint64_t)(interrupt_stack + sizeof(interrupt_stack));
+    proc->context->iret_rip = code;
+    proc->kernel_stack = kalloc_stack();
+    if (!proc->kernel_stack) panic(NULL, "failed to allocate kernel stack");
 
-    // Load user_pml4 into cr3 along here??
+    // 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));
-
-    // Copy code into user pages
     memcpy((uint64_t*)code, exec_addr, exec_size);
+    load_cr3(VIRT_TO_PHYS((uint64_t)kernel_pml4));
 
-    process_jump_to_user(stack_top, code);
+    process_add(&processes_list, proc);
+    DEBUG("user process '%s' (pid=%u) enqueued for scheduling", name, proc->pid);
+    SET_INTERRUPTS;
 }

src/sched/scheduler.c

@@ -9,17 +9,21 @@
 #include <mem/paging.h>
 #include <stdint.h>
 #include <io/serial/serial.h>
+#include <arch/gdt.h>
 
 extern struct process* processes_list;
 extern struct process* current_process;
 extern struct process* idle_proc;
 
+extern struct tss tss;
+
 /*
  * scheduler_init - Choose the first process
  */
 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);
 }
 
 /*
@@ -39,42 +43,56 @@ struct cpu_status* scheduler_schedule(struct cpu_status* 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;
 
-    for (;;) {
+    if (current_process->status == DEAD) {
-        struct process* 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;
-            current_process = current_process->next;
+
-        } else {
+        process_delete(&processes_list, dead_process);
-            current_process = processes_list;
+
-        }
+        if (processes_list == NULL || next_process == dead_process) {
-        
+            current_process = idle_proc;
-        if (current_process != NULL && current_process->status == DEAD) {
-            process_delete(&prev_process, current_process);
-            current_process = NULL;
             return idle_proc->context;
-        } else {
-            current_process->status = RUNNING;
-/*             if (prev_process != current_process) {
-                DEBUG("Changed from {pid=%u, name=%s} to {pid=%u, name=%s}", prev_process->pid, prev_process->name, current_process->pid, current_process->name);
-            } */
-            break;
         }
+
+        current_process = next_process;
+    } else if (current_process->next != NULL) {
+        current_process = current_process->next;
+    } else {
+        current_process = processes_list;
     }
 
-    //DEBUG("current_process={pid=%u, name='%s', root_page_table[virt]=%p}", current_process->pid, current_process->name, current_process->root_page_table);
+    for (;;) {
+        if (current_process->status == DEAD) {
+            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;
+            }
+
+            current_process = next_process;
+            continue;
+        }
+
+        current_process->status = RUNNING;
+        break;
+    }
+
+    // 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;
 }

user/hello.S

@@ -12,5 +12,10 @@ hello:
     mov rdx, 33         ;count
     int 0x80
 
+.end:
+    mov rax, 0x3C       ;sys_exit
+    mov rdi, 0x0        ;error_code
+    int 0x80
+
 .loop:
     jmp .loop

user/pedicel.S

@@ -0,0 +1,25 @@
+bits 64
+
+section .data
+hello db 0x0A, 0x0D, "User program 2 speaking", 0
+
+section .text
+
+_start:
+    mov rax, 0x1    ;sys_write
+    mov rdi, 0x1    ;stdout
+    lea rsi, [rel hello]
+    mov rdx, 25     ;count
+    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