kernel multitasking

.gdb_history

@@ -0,0 +1,256 @@
+ni
+ni
+c
+ni
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+c
+ni
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+target remote localhost:1234
+target remote localhost:1234
+ni
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+c
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+c
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+b pit_isr
+c
+target remote localhost:1234
+c
+ni
+ni
+ni
+ni
+ni
+c
+target remote localhost:1234
+target remote localhost:1234
+c
+ni
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+ni
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Makefile

@@ -20,7 +20,7 @@ ISO := Hazel.iso
 CFLAGS    := -ffreestanding -Wall -Wextra -Werror -I $(INCLUDEDIR) -I lib
 LDFLAGS   := -ffreestanding -nostdlib -lgcc -T kernel/kernel.ld
 QEMUFLAGS := -cdrom $(BUILDDIR)/$(ISO) \
-			 -s -d int \
+	 -s \
 	     -m 512M \
 	     -serial stdio
 

include/kernel/pit.h

@@ -17,6 +17,6 @@
 #define DIVISOR (PIT_FREQUENCY/DESIRED_FREQUENCY)
 
 void pit_init(void);
-void pit_handler(void);
+int pit_handler(void);
 
 #endif

include/kernel/task.h

@@ -11,6 +11,7 @@ typedef struct {
 } task_t;
 
 int task_init(task_t *task, elf_t *elf);
+void task_sort();
 void schedule(void);
 
 #endif

kernel/init.asm

@@ -86,10 +86,28 @@ halt:
     hlt
     jmp halt
 
+extern ctx
+extern task_sort
 global pit_isr
 pit_isr:
+    pushad
     extern pit_handler
     call pit_handler
+    cmp eax, 1
+    jne .ret
+
+    mov edi, [ctx+28] ; EDI = current task
+    ; mov esi, [edi+8]  ; ESI = next task
+    ; Save current ESP
+    mov dword [edi], esp
+    call task_sort
+    mov edi, [ctx+28] ; EDI = NEW current task
+    ; Set current task to next task
+    ; mov dword [ctx+28], esi
+    ; Change to new ESP
+    mov esp, [edi]
+.ret:
+    popad
     iret
 
 global jmp_user_mode
@@ -115,31 +133,6 @@ flush_tss:
     ltr [esp+4]
     ret
 
-extern ctx
-global task_switch
-task_switch:
-    ; Save current task's registers
-    push ebx
-    push esi
-    push edi
-    push ebp
-
-    mov edi, [ctx+28] ; EDI = current task
-    mov esi, [esp+20] ; ESI = next task
-    ; Save current ESP
-    mov dword [edi], esp
-    ; Set current task to next task
-    mov dword [ctx+28], esi
-    ; Change to new ESP
-    mov esp, [esi]
-    mov ecx, [esi+4]
-
-    pop ebp
-    pop edi
-    pop esi
-    pop ebx
-    ret
-
 extern exception_handler
 %macro isr_err_stub 1
 isr_stub_%+%1:

kernel/kernel.c

@@ -28,6 +28,7 @@ void exception_handler(int_stack_frame_t r) {
             r.int_no, r.err_code, r.eax, r.ecx, r.edx, r.ebx, r.esi, r.edi, r.ebp, r.esp+24); 
     LOG("\nEIP:     0x%08X\nCS:      0x%08X\nEFLAGS:  0x%08X\n",
             r.eip, r.cs, r.eflags);
+    for (;;) {}
 }
 
 void sleep(int delay) {
@@ -49,10 +50,9 @@ void idt_init(void) {
 }
 
 void test(void) {
-    for (int i = 0; i < 1000; i++) {
-        LOG("O");
+    for (;;) {
+	LOG("B");
     }
-    task_switch((task_t *)ctx.current_task->next);
 }
 
 void kernel(multiboot_info_t *info) {
@@ -69,12 +69,12 @@ void kernel(multiboot_info_t *info) {
     LOG("%d bytes of RAM detected\nCreated a %d byte large physical memory map at 0x%08X\n", ctx.mmap_size*BLOCK_SIZE*8, ctx.mmap_size, (uint32_t)ctx.mmap);
 
     idt_init();
-/*
+
     pic_remap(PIC_1_START, PIC_2_START);
     asm volatile ("sti" ::);
     ctx.ticks = 0;
     pit_init();
-*/
+
     // Setup TSS
     uint32_t base = (uint32_t)&tss;
     uint32_t limit = base + sizeof(tss_t);
@@ -101,20 +101,24 @@ void kernel(multiboot_info_t *info) {
 
     uint32_t *stack = mmap_find_first_free_block();
     asm volatile ("mov %%esp, %0" : "=r" (task1.esp));
-    stack[1023] = (uint32_t)test;
-    stack[1022] = 0;
-    stack[1021] = 0;
-    stack[1020] = 0;
-    stack[1019] = 0;
-    task2.esp = (uint32_t)stack + (0x1000 - 20);
+    stack[1023] = 0x207;
+    stack[1022] = 0x8;
+    stack[1021] = (uint32_t)test;
+    stack[1020] = 0xDEADBEEF;
+    stack[1019] = 0xDEADBEEF;
+    stack[1018] = 0xDEADBEEF;
+    stack[1017] = 0xDEADBEEF;
+    stack[1016] = 0xDEADBEEF;
+    stack[1015] = 0xDEADBEEF;
+    stack[1014] = 0xDEADBEEF;
+    stack[1013] = 0xDEADBEEF;
+    task2.esp = (uint32_t)stack + (0x1000 - 44);
     task2.cr3 = (uint32_t)boot_page_dir - KERNEL_VMA;
-    task2.next = (uint32_t *)&task1;
-    //task_switch(&task2);
-    for (int i = 0; i < 1000; i++) {
-        LOG("_");
+    task2.next = 0;
+
+    for (;;) {
+	LOG("A");
     }
-    task_switch((task_t *)ctx.current_task->next);
-    task_switch((task_t *)ctx.current_task->next);
 
     /*
     multi_mod_t *init = (multi_mod_t *)(info->moduleaddress + KERNEL_VMA);

kernel/pit.c

@@ -14,19 +14,13 @@ void pit_init(void) {
 
 extern void task_switch(task_t *task);
 
-void pit_handler(void) {
+int pit_handler(void) {
     ctx.ticks++;
 
-    if (ctx.current_task->next) {
-        LOG("TASK SWITCH\n");
-        //task_t *old = ctx.current_task;
-        //task_t *new = (task_t *)ctx.current_task->next;
-        //new->next = (uint32_t *)old;
-        //old->next = (uint32_t *)new;
-       task_switch((task_t *)ctx.current_task->next);
-    }
-
     outb(PIT_CHAN0_DATA, (uint8_t)(DIVISOR & 0xff));
     outb(PIT_CHAN0_DATA, (uint8_t)((DIVISOR & 0xff00) >> 8));
     pic_send_eoi(0);
+
+    if ((ctx.ticks % 3) == 0) return 1;
+    else return 0;
 }

kernel/task.c

@@ -7,7 +7,7 @@ extern kernel_ctx_t ctx;
 int task_init(task_t *task, elf_t *elf) {
     section_t *text = elf_find_section(elf, ".text");
     if (!text) return 0;
-    task->eip = elf->e_entry + text->sh_offset;
+    //task->eip = elf->e_entry + text->sh_offset;
     // Allocate a page for a stack
     task->esp = (uint32_t)mmap_find_first_free_block() + 0x1000;
 
@@ -33,6 +33,21 @@ int task_init(task_t *task, elf_t *elf) {
     return 1;
 }
 
+void task_sort() {
+    if (!ctx.current_task || !ctx.current_task->next) return; // If the list is empty or has only one node
+
+    task_t* new_head = (task_t *)ctx.current_task->next;
+    task_t* temp = new_head;
+
+    while (temp->next) {
+	temp = (task_t *)temp->next;
+    }
+
+    temp->next = (uint32_t *)ctx.current_task;
+    ctx.current_task->next = 0;
+    ctx.current_task = new_head;
+}
+
 void schedule(void) {
     // If there's only one task running
     if (!ctx.current_task->next) return;

peda-session-kernel.bin.txt

@@ -0,0 +1,2 @@
+break pit_isr
+