From 5f025d18bff04d5affa76cd9cf10c12f73a65dd0 Mon Sep 17 00:00:00 2001
From: rami <rami.kaldany@pm.me>
Date: Sat, 6 Jul 2024 18:00:06 -0400
Subject: [PATCH] task switch progress

---
 bochsrc               |  2 +-
 include/kernel/task.h |  1 -
 kernel/init.asm       | 22 +++++++++++-----------
 kernel/kernel.c       | 39 +++++++++++++++++++++++++++++++++++----
 kernel/pit.c          | 11 +++++++++++
 5 files changed, 58 insertions(+), 17 deletions(-)

diff --git a/bochsrc b/bochsrc
index 387e109..f5de00b 100644
--- a/bochsrc
+++ b/bochsrc
@@ -2,4 +2,4 @@ ata0-slave: type=cdrom, path=./build/Hazel.iso, status=inserted
 magic_break: enabled=1
 boot: cdrom
 
-display_library: x
+display_library: sdl2
diff --git a/include/kernel/task.h b/include/kernel/task.h
index 786f61d..72cf9ef 100644
--- a/include/kernel/task.h
+++ b/include/kernel/task.h
@@ -5,7 +5,6 @@
 #include <kernel/elf.h>
 
 typedef struct {
-    uint32_t eip;
     uint32_t esp;
     uint32_t cr3;
     uint32_t *next;
diff --git a/kernel/init.asm b/kernel/init.asm
index 948cb4a..9c3e8b6 100644
--- a/kernel/init.asm
+++ b/kernel/init.asm
@@ -118,22 +118,22 @@ flush_tss:
 extern ctx
 global task_switch
 task_switch:
+    ; Save current task's registers
     push ebx
     push esi
     push edi
     push ebp
 
-    mov esi, [ctx+28]
-    ; Return if only one process is running
-    mov eax, [esi+12]
-    cmp eax, 0
-    je ret
-    ; Check if using same virtual memory
-    cmp [esi+8], [eax+8]
-    je .ret
-    mov ecx, [eax+8]
-    mov cr3, ecx
-.ret:    
+    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
diff --git a/kernel/kernel.c b/kernel/kernel.c
index f8c12a9..804fa85 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -18,6 +18,7 @@ extern uint32_t isr_stub_table[32];
 extern void pit_isr(void);
 extern void jmp_user_mode(uint32_t esp, uint32_t eip);
 extern void flush_tss(uint32_t segment_selector);
+extern void task_switch(task_t *task);
 extern gdt_t gdt[6];
 extern uint32_t boot_page_dir[1024];
 extern uint32_t boot_page_tab[1024];
@@ -35,7 +36,7 @@ void sleep(int delay) {
 	cpu_relax;
 }
 
-void idt_init() {
+void idt_init(void) {
     for (int i = 0; i < 32; i++) {
         idt_encode_entry(idt, i, isr_stub_table[i], GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, RING0), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
     }
@@ -47,6 +48,13 @@ void idt_init() {
     asm volatile ("lidt %0" :: "m"(idtr));
 }
 
+void test(void) {
+    for (int i = 0; i < 1000; i++) {
+        LOG("O");
+    }
+    task_switch((task_t *)ctx.current_task->next);
+}
+
 void kernel(multiboot_info_t *info) {
     if (!CHECK_FLAG(info->flags, 3))  goto halt;   // Modules
     if (!CHECK_FLAG(info->flags, 6))  goto halt;  // Memory map
@@ -61,14 +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);
@@ -87,6 +93,30 @@ void kernel(multiboot_info_t *info) {
     tss.ss = tss.ds = tss.es = tss.fs = tss.gs = GDT_SEGMENT_SELECTOR(GDT_USER_DATA, RING3);
     flush_tss(GDT_SEGMENT_SELECTOR(5, RING3));
 
+    task_t task1 = {0};
+    task_t task2 = {0};
+    task1.cr3 = (uint32_t)boot_page_dir - KERNEL_VMA;
+    task1.next = (uint32_t *)&task2;
+    ctx.current_task = &task1;
+
+    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);
+    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("_");
+    }
+    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);
     elf_t *elf = (elf_t *)(init->mod_start+KERNEL_VMA);
     task_t task = {0};
@@ -97,6 +127,7 @@ void kernel(multiboot_info_t *info) {
 
     LOG("Switching to ring 3... EIP: 0x%08X ESP: 0x%08X\n", task.eip, task.esp);
     jmp_user_mode(task.esp, task.eip); 
+    */
 
 halt:
     for (;;) {}
diff --git a/kernel/pit.c b/kernel/pit.c
index 9ea19f9..aca8feb 100644
--- a/kernel/pit.c
+++ b/kernel/pit.c
@@ -12,9 +12,20 @@ void pit_init(void) {
     outb(PIT_CHAN0_DATA, (uint8_t)((DIVISOR & 0xff00) >> 8));
 }
 
+extern void task_switch(task_t *task);
+
 void 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);