tasking: add simple base for running things in ring 3

src/tasking/switch.asm

@@ -94,3 +94,24 @@ switchProcess:
      ; |------------------------|
 
      ret
+
+global jump_usermode
+extern test_user_function
+jump_usermode:
+	mov ax, (4 * 8) | 3 ; ring 3 data with bottom 2 bits set for ring 3
+	mov ds, ax
+	mov es, ax 
+	mov fs, ax 
+	mov gs, ax ; SS is handled by iret
+
+	; and eax, ~0x80000000
+	; mov cr0, eax
+
+	; set up the stack frame iret expects
+	mov eax, esp
+	push (4 * 8) | 3 ; data selector
+	push eax ; current esp
+	pushf ; eflags
+	push (3 * 8) | 3 ; code selector (ring 3 code with bottom 2 bits set for ring 3)
+	push test_user_function ; instruction address to return to
+	iret

src/tasking/sys_exit.asm

@@ -0,0 +1,41 @@
+; TODO: maybe put it near idt.c?
+global sys_exit_handler
+extern printf
+sys_exit_handler:
+    ; Сохраняем регистры Ring 3
+    pusha
+    push ds
+    push es
+    push fs
+    push gs
+
+    ; Переключаемся на сегменты Ring 0
+    mov ax, 0x10  ; Селектор данных Ring 0 (gdt_data)
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+
+    ; Выполняем действие
+    push sys_exit_msg
+    call printf
+    add esp, 4
+
+    ; Восстанавливаем сегменты Ring 3
+    pop gs
+    pop fs
+    pop es
+    pop ds
+    popa
+
+    ; Возвращаемся в Ring 3
+    iret
+
+global test_user_function
+test_user_function:
+	mov eax, 0xDEADBEEF
+	int 0x80
+	jmp $
+
+section .data
+sys_exit_msg: db "Returned from Ring 3", 0

src/tasking/task.c

@@ -107,14 +107,68 @@ void task2(int arg1, int arg2)
 	while(1){printf("task2 %X %X\n", arg1, arg2);}
 }
 
+void jump_usermode2(void);
+
 void scheduler_init()
 {
+	jump_usermode2();
 	//we create this task two times because in other case it just won't start
-	task_create((EntryPoint)&idle, NULL, 0);
-	task_create((EntryPoint)&idle, NULL, 0);
+	//task_create((EntryPoint)&idle, NULL, 0);
+	//task_create((EntryPoint)&idle, NULL, 0);
 
 	void* args1[] = {(void*)42, (void*)"ebalo"};
-	task_create((EntryPoint)&task1, args1, 2);
+	//task_create((EntryPoint)&task1, args1, 2);
 	void* args2[] = {(void*)69, (void*)420};
-	task_create((EntryPoint)&task2, args2, 2);
+	//task_create((EntryPoint)&task2, args2, 2);
+}
+
+extern void test_user_function(void);
+void jump_usermode2(void) {
+    void* code_phys = alloc_page();
+    if (!code_phys) {
+        printf("No memory for user code\n");
+        while (1);
+    }
+
+    // Временно отображаем code_phys в ядре
+    uint32_t kernel_temp_virt = 0xC0100000;
+    map_page(code_phys, (void*)kernel_temp_virt, 0x3); // Present, R/W, Supervisor
+
+    // Копируем код
+    uint32_t* src = (uint32_t*)test_user_function;
+    uint32_t* dst = (uint32_t*)kernel_temp_virt;
+    for (int i = 0; i < 1024; i++) {
+        dst[i] = src[i];
+    }
+    printf("Copied code to 0x%x (virt 0x%x): 0x%x 0x%x 0x%x\n",
+           (uint32_t)code_phys, kernel_temp_virt, dst[0], dst[1], dst[2]);
+
+    // Настраиваем Ring 3
+    uint32_t user_stack_top;
+    void* user_code_virt = setup_user_process(code_phys, &user_stack_top);
+    if (!user_code_virt) {
+        printf("Failed to setup user process\n");
+        while (1);
+    }
+
+    printf("user_code_virt: 0x%x, user_stack_top: 0x%x\n",
+           (uint32_t)user_code_virt, user_stack_top);
+
+    asm volatile (
+        "mov $0x23, %%dx\n"
+        "mov %%dx, %%ds\n"
+        "mov %%dx, %%es\n"
+        "mov %%dx, %%fs\n"
+        "mov %%dx, %%gs\n"
+        "push $0x23\n"
+        "push %0\n"
+        "pushf\n"
+        "push $0x1B\n"
+        "push %1\n"
+        "iret\n"
+        :
+        : "r" (user_stack_top), "r" (user_code_virt)
+        : "dx", "memory"
+    );
+    __builtin_unreachable();
 }