enable paging

include/kernel/kernel.h

@@ -16,4 +16,57 @@ typedef struct {
    uint64_t ticks;
 } kernel_ctx_t;
 
+#define GDT_NULL 0
+#define GDT_KERNEL_CODE 1
+#define GDT_KERNEL_DATA 2
+#define GDT_USER_CODE 3
+#define GDT_USER_DATA 4
+
+#define RING0 0
+#define RING3 3
+
+#define GDT_SEGMENT_SELECTOR(i, p) ((i << 3) | p)
+
+struct gdt_entry {
+    uint16_t limit_low;
+    uint16_t base_low;
+    uint8_t base_middle;
+    uint8_t access;
+    uint8_t granularity;
+    uint8_t base_high;
+} __attribute__((packed));
+typedef struct gdt_entry gdt_t;
+
+struct tss_entry {
+    uint32_t prev_tss;    // The previous TSS - with hardware task switching this is used
+    uint32_t esp0;        // The stack pointer to load when we change to kernel mode
+    uint32_t ss0;         // The stack segment to load when we change to kernel mode
+    uint32_t esp1;        // Unused...
+    uint32_t ss1;
+    uint32_t esp2;
+    uint32_t ss2;
+    uint32_t cr3;
+    uint32_t eip;
+    uint32_t eflags;
+    uint32_t eax;
+    uint32_t ecx;
+    uint32_t edx;
+    uint32_t ebx;
+    uint32_t esp;
+    uint32_t ebp;
+    uint32_t esi;
+    uint32_t edi;
+    uint32_t es;          // The value to load into ES when we change to kernel mode
+    uint32_t cs;          // The value to load into CS when we change to kernel mode
+    uint32_t ss;          // The value to load into SS when we change to kernel mode
+    uint32_t ds;          // The value to load into DS when we change to kernel mode
+    uint32_t fs;          // The value to load into FS when we change to kernel mode
+    uint32_t gs;          // The value to load into GS when we change to kernel mode
+    uint32_t ldt;         // Unused...
+    uint16_t trap;
+    uint16_t iomap_base;
+} __attribute__((packed));
+typedef struct tss_entry tss_t;
+
+
 #endif

kernel/init.asm

@@ -75,6 +75,23 @@ jmp_user_mode:
 
     iret
 
+global flush_tss
+flush_tss:
+    ltr [esp+4]
+    ret
+
+global enable_paging
+enable_paging:
+    push eax
+    mov eax, [esp+4]
+    mov cr3, eax
+
+    mov eax, cr0
+    or eax, 0x80000000
+    mov cr0, eax
+    pop eax
+    ret
+
 extern exception_handler
 %macro isr_err_stub 1
 isr_stub_%+%1:
@@ -174,6 +191,8 @@ gdt_user_data:
     db 0b11110010
     db 0b11001111
     db 0x00
+tss:
+    dq 0
 gdt_end:
 
 gdtp:

kernel/kernel.c

@@ -5,18 +5,19 @@
 #include <kernel/idt.h>
 #include <kernel/pic.h>
 #include <kernel/pit.h>
+#include <stdint.h>
 
 kernel_ctx_t ctx = {0};
 struct idt_entry idt[256] = {0};
 struct idtr idtr = {0};
+tss_t tss = {0};
 
 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);
-void test_entry(void) {
+extern gdt_t gdt[6];
-    for (;;) {}
+extern void enable_paging(uint32_t *page_directory);
-}
 
 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",
@@ -31,6 +32,15 @@ void sleep(int delay) {
 	cpu_relax;
 }
 
+typedef struct {
+    uint32_t eip;
+    uint32_t esp;
+    uint32_t cr3;
+} task_t;
+
+__attribute__((aligned(4096))) uint32_t page_dir[1024];
+__attribute__((aligned(4096))) uint32_t page_tab[1024];
+
 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
@@ -47,21 +57,59 @@ void kernel(multiboot_info_t *info) {
     for (int i = 0; i < 32; i++) {
         idt_encode_entry(idt, i, isr_stub_table[i], GDT_SEGMENT_SELECTOR(1, 0), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
     }
-    idt_encode_entry(idt, 32, (uint32_t)pit_isr, GDT_SEGMENT_SELECTOR(1, 0), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
+    idt_encode_entry(idt, 32, (uint32_t)pit_isr, GDT_SEGMENT_SELECTOR(1, 0), INT_GATE_32 | INT_RING0 | INT_PRESENT);
     
     idtr.size = (sizeof(struct idt_entry) * 256) - 1;
     idtr.base = (uint32_t) idt;
 
     asm volatile ("lidt %0" :: "m"(idtr));
     pic_remap(PIC_1_START, PIC_2_START);
-    //asm volatile ("sti" ::);
+    /*
+    asm volatile ("sti" ::);
 
     ctx.ticks = 0;
-    //pit_init();
+    pit_init();
+
+    uint32_t base = (uint32_t)&tss;
+    uint32_t limit = base + sizeof(tss_t);
+    gdt[5].base_low = base & 0xFFFF;
+    gdt[5].base_middle = (base >> 16) & 0xFF;
+    gdt[5].base_high = (base >> 24) & 0xFF;
+    gdt[5].limit_low = limit & 0xFFFF;
+    gdt[5].granularity = (limit >> 16) & 0x0F;
+    gdt[5].granularity |= 0x40;
+    gdt[5].access = 0x89;
+    tss.ss0 = GDT_SEGMENT_SELECTOR(2, RING0);
+    tss.esp0 = 0;
+    tss.cs = GDT_SEGMENT_SELECTOR(3, RING3);
+    tss.ss = tss.ds = tss.es = tss.fs = tss.gs = GDT_SEGMENT_SELECTOR(4, RING3);
+    flush_tss(GDT_SEGMENT_SELECTOR(5, RING3));
+    */
+
+#define PAGE_PRESENT (1<<0)
+#define PAGE_RW (1<<1)
+#define PAGE_USER (1<<2)
+
+#define PAGE_DIR_INDEX(x) (((x) >> 22) & 0x3FF)
+#define PAGE_TAB_INDEX(x) (((x) >> 12) & 0x3FF)
+#define PAGE_OFFSET(x) ((x) & 0xFFF)
+
+    LOG("Page directory: %08X -- Page table: %08X\n", page_dir, page_tab);
+
+    for (int i = 0; i < 1024; i++) {
+	page_tab[i] = (i * 0x1000) | PAGE_PRESENT | PAGE_RW | PAGE_USER;
+    }
+
+    for (int i = 0; i < 1024; i++) {
+	page_dir[i] = ((uint32_t)page_tab) | PAGE_PRESENT | PAGE_RW | PAGE_USER;
+    }
+
+    enable_paging(page_dir);
 
     uint32_t stack = (uint32_t)mmap_find_first_free_block();
     multi_mod_t *init = (multi_mod_t *)info->moduleaddress;
-    LOG("Switching to ring 3... EIP: 0x%08X ESP: 0x%08X", init->mod_start, stack+0x1000);
+    LOG("Switching to ring 3... EIP: 0x%08X ESP: 0x%08X\n", init->mod_start, stack+0x1000);
+
     jmp_user_mode(stack+0x1000, init->mod_start); 
 
 halt: