tasking: add simple base for running things in ring 3

Makefile

@@ -2,7 +2,7 @@
 OBJS = bin/boot.o bin/kernel.o bin/idt.o bin/isr.o bin/screen.o \
 	bin/utils.o bin/string.o bin/stdio.o bin/disk.o bin/pic.o bin/pit.o \
 	bin/keyboard.o bin/paging.o bin/heap.o bin/page_alloc.o bin/page_tables.o \
-	bin/fat.o bin/task.o bin/switch.o
+	bin/fat.o bin/task.o bin/switch.o bin/sys_exit.o
 
 # Define the compiler and assembler
 CC = gcc -D__is_katauos
@@ -114,6 +114,9 @@ bin/switch.o: src/tasking/switch.asm
 bin/task.o: src/tasking/task.c
 	$(CC) $(CFLAGS) -c $< -o $@
 
+bin/sys_exit.o: src/tasking/sys_exit.asm
+	$(AS) $(ASFLAGS) $< -o $@
+
 clean:
 	rm -rf bin/
 	rm -f $(OUTPUT)

include/paging.h

@@ -7,6 +7,7 @@
 
 extern uint32_t kernel_page_directory[1024] __attribute__((aligned(4096)));
 extern uint32_t kernel_page_table[1024] __attribute__((aligned(4096)));
+extern uint32_t user_page_table[1024] __attribute__((aligned(4096)));
 
 
 //paging.c
@@ -24,6 +25,7 @@ void free_page(void* physaddr);
 void *get_physaddr(void *virtualaddr);
 void map_page(void* physaddr, void* virtualaddr, unsigned int flags);
 void map_kernel_page(void* virtualaddr, unsigned int flags);
+void* setup_user_process(void* user_code_phys, uint32_t* user_stack_top);
 
 //heap.c
 void heap_init();

src/kernel/isr.c

@@ -22,6 +22,8 @@ __attribute__((interrupt)) void isr_timer(struct interrupt_frame *frame);
 void isr_custom();
 void default_handler();
 
+extern void sys_exit_handler();
+
 void isr_install() {
     idt_set_descriptor(0, (uint32)isr0, 0x8E);
     idt_set_descriptor(1, (uint32)isr1, 0x8E);
@@ -62,6 +64,7 @@ void isr_install() {
     idt_set_descriptor(0x20, (uint32)isr_timer, 0x8E);
     idt_set_descriptor(0x21, (uint32)isr_custom, 0x8E);
 
+    idt_set_descriptor(0x80, (uint32)sys_exit_handler, 0xEE);
 
     idt_set(); // Load with ASM
     printf("isr_install done\n");

src/mm/page_tables.c

@@ -1,6 +1,26 @@
 #include "../include/paging.h"
 #include <stdint.h>
 
+static uint32_t next_user_virt = 0x00400000;
+void* setup_user_process(void* user_code_phys, uint32_t* user_stack_top) {
+    void* stack_phys = alloc_page();
+    if (!stack_phys) return 0;
+
+    uint32_t code_virt = next_user_virt;
+    uint32_t stack_virt = code_virt + 0x3FF000; // 4 МБ - 4 КБ
+    map_page(user_code_phys, (void*)code_virt, 0x7);
+    map_page(stack_phys, (void*)stack_virt, 0x7);
+
+    *user_stack_top = stack_virt + 0x1000;
+    next_user_virt += 0x400000; // Следующий 4 МБ блок
+    return (void*)code_virt;
+}
+
+void free_user_process(void* code_phys, void* stack_phys) {
+    free_page(code_phys);
+    free_page(stack_phys);
+}
+
 void *get_physaddr(void *virtualaddr) {
     unsigned long pdindex = (unsigned long)virtualaddr >> 22;
     unsigned long ptindex = (unsigned long)virtualaddr >> 12 & 0x03FF;

src/mm/paging.c

@@ -3,6 +3,8 @@
 
 uint32_t kernel_page_directory[1024] __attribute__((aligned(4096)));
 uint32_t kernel_page_table[1024] __attribute__((aligned(4096)));
+uint32_t user_page_table[1024] __attribute__((aligned(4096)));
+
 
 void enablePaging() {
     asm volatile (
@@ -35,8 +37,9 @@ void paging_init() {
     // Проверяем физические адреса
     uint32_t pd_phys = (uint32_t)kernel_page_directory;
     uint32_t pt_phys = (uint32_t)kernel_page_table;
+    uint32_t user_pt_phys = (uint32_t)user_page_table;
 
-    if (pd_phys & 0xFFF || pt_phys & 0xFFF) {
+    if (pd_phys & 0xFFF || pt_phys & 0xFFF || user_pt_phys & 0xFFF) {
         while (1); // Ошибка выравнивания
     }
 
@@ -51,6 +54,12 @@ void paging_init() {
     }
     kernel_page_directory[0] = pt_phys | 0x3;
 
+    // Ring 3: 0x00400000–0x007FFFFF, User-accessible
+    for (i = 0; i < 1024; i++) {
+        user_page_table[i] = 0; // Изначально не отображено
+    }
+    kernel_page_directory[1] = user_pt_phys | 0x7; // Present, R/W, User
+
     // Рекурсивное отображение
     kernel_page_directory[1023] = pd_phys | 0x3;
 

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();
 }