start syscalls

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 \
+	 -s -d int \
 	     -m 512M \
 	     -serial stdio
 

include/kernel/idt.h

@@ -45,6 +45,10 @@ typedef struct {
     uint32_t eflags;
 } int_stack_frame_t;
 
+typedef struct {
+    uint32_t edi, esi, ebp, esp, ebx, edx, ecx, eax; /*  Pushed by pusha. */
+} stack_frame_t;
+
 void idt_encode_entry(struct idt_entry idt[], int i, uint32_t offset, uint16_t segment_selector, uint8_t attributes);
 
 #endif

include/kernel/task.h

@@ -8,6 +8,7 @@ typedef struct {
     uint32_t esp;
     uint32_t cr3;
     uint32_t *next;
+    uint32_t eip;
 } task_t;
 
 int task_init(task_t *task, elf_t *elf);

kernel/init.asm

@@ -94,7 +94,8 @@ pit_isr:
     extern pit_handler
     call pit_handler
     cmp eax, 1
-    jne .ret
+    ; jne .ret
+    jmp .ret
 
     mov edi, [ctx+28] ; EDI = current task
     ; mov esi, [edi+8]  ; ESI = next task
@@ -133,6 +134,25 @@ flush_tss:
     ltr [esp+4]
     ret
 
+global syscall_isr
+syscall_isr:
+    pushad
+    mov ecx, esp
+    sysenter
+after_syscall:
+    popad
+    iret
+
+global syscall
+syscall:
+    imul eax, eax, 4
+    add eax, syscall_table
+    pushad
+    call [eax]
+    popad
+    mov edx, after_syscall
+    sysexit
+
 extern exception_handler
 %macro isr_err_stub 1
 isr_stub_%+%1:
@@ -247,6 +267,13 @@ global boot_page_tab
 align 0x1000
 boot_page_tab: times 1024 dd 0
 
+global syscall_table
+syscall_table:
+    dd 0
+
+    extern syscall_write
+    dd syscall_write
+
 section .bss
 align 16
 stack_top:

kernel/kernel.c

@@ -19,10 +19,16 @@ 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 void syscall(void);
+extern void syscall_isr(void);
 extern gdt_t gdt[6];
 extern uint32_t boot_page_dir[1024];
 extern uint32_t boot_page_tab[1024];
 
+void syscall_write(stack_frame_t r) {
+    LOG("SYSCALL %08X\n", r.eax);
+}
+
 void exception_handler(int_stack_frame_t r) {
     LOG("Exception 0x%X (0x%X) has occurred\nEAX: 0x%08X\nECX: 0x%08X\nEDX: 0x%08X\nEBX: 0x%08X\nESI: 0x%08X\nEDI: 0x%08X\nEBP: 0x%08X\nESP: 0x%08X\n",
             r.int_no, r.err_code, r.eax, r.ecx, r.edx, r.ebx, r.esi, r.edi, r.ebp, r.esp+24); 
@@ -42,6 +48,7 @@ void idt_init(void) {
         idt_encode_entry(idt, i, isr_stub_table[i], GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, RING0), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
     }
     idt_encode_entry(idt, 32, (uint32_t)pit_isr, GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, RING0), INT_GATE_32 | INT_RING0 | INT_PRESENT);
+    idt_encode_entry(idt, 0x80, (uint32_t)syscall_isr, GDT_SEGMENT_SELECTOR(GDT_USER_CODE, RING3), INT_GATE_32 | INT_RING3 | INT_PRESENT);
     
     idtr.size = (sizeof(struct idt_entry) * 256) - 1;
     idtr.base = (uint32_t) idt;
@@ -93,6 +100,7 @@ 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;
@@ -115,12 +123,8 @@ void kernel(multiboot_info_t *info) {
     task2.esp = (uint32_t)stack + (0x1000 - 44);
     task2.cr3 = (uint32_t)boot_page_dir - KERNEL_VMA;
     task2.next = 0;
+    */
 
-    for (;;) {
-	LOG("A");
-    }
-
-    /*
     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};
@@ -129,9 +133,41 @@ void kernel(multiboot_info_t *info) {
     ctx.current_task = &task;
     asm volatile ("mov %0, %%cr3" :: "r"(task.cr3));
 
+    // Set the ring0 CS
+    asm volatile (
+        "movl $0x174, %%ecx \n\t"
+        "movl %0, %%eax \n\t"
+        "xor %%edx, %%edx \n\t"
+        "wrmsr"
+        : 
+        : "r"(GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, RING0))
+        : "eax", "ecx", "edx"
+    );
+    // Set the ring0 stack
+    uint32_t *k_stack = mmap_find_first_free_block();
+    asm volatile (
+        "movl $0x175, %%ecx \n\t"   
+        "movl %0, %%eax \n\t"       
+        "xor %%edx, %%edx \n\t"     
+        "wrmsr"
+        : 
+        : "r"((uint32_t)k_stack + 0x1000)
+        : "eax", "ecx", "edx"
+    );
+    // Set the ring0 syscall entry
+    asm volatile (
+        "movl $0x176, %%ecx \n\t"   // MSR address
+        "movl %0, %%eax \n\t"       // Lower 32 bits (eip)
+        "xor %%edx, %%edx \n\t"     // Upper 32 bits (zero for 32-bit value)
+        "wrmsr"
+        : 
+        : "r"(syscall)
+        : "eax", "ecx", "edx"
+    );
+
+
     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 (;;) {}

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;
 
@@ -16,7 +16,7 @@ int task_init(task_t *task, elf_t *elf) {
     uint32_t *page_tab = mmap_find_first_free_block();
     for (int i = 0; i < 1024; i++) {
 	// Map kernel to 3GiB
-	if (i == 768) page_dir[i] = ((uint32_t)boot_page_tab - KERNEL_VMA) | 3;
+	if (i == 768) page_dir[i] = ((uint32_t)boot_page_tab - KERNEL_VMA) | 7;
 	// Map 3.4GiB-4GiB as non-present kernel entries
 	else if (i > 768) page_dir[i] = 4;
 	// Map remaining entries as non-present u/s

user/userinit.asm

@@ -1,5 +1,7 @@
 [bits 32]
 global _start
 _start:
-    mov eax, 0xDEADBEEF
+    mov ecx, 0xDEADBEEF
+    mov eax, 1
+    int 0x80
     jmp $