feat: gdt

src/kernel/archs/hal.h

@@ -2,7 +2,7 @@
 
 #include <io/stream.h>
 
-void hal_setup(void);
+Res hal_setup(void);
 
 /* --- Assembly function --------------------------------------------------- */
 

src/kernel/archs/x86_64/gdt.c

@@ -0,0 +1,81 @@
+#include <dbg/log.h>
+#include <hal.h>
+#include <string.h>
+#include <sync/spinlock.h>
+
+#include "gdt.h"
+
+static Gdt gdt = {0};
+
+static Spinlock lock = SPINLOCK_INIT;
+
+static GdtDescriptor gdt_desc = {
+    .size = sizeof(gdt) - 1,
+    .offset = (uintptr_t)&gdt,
+};
+
+static void gdt_lazy_init(GdtEntry self[static 1], uint8_t access, uint8_t flags)
+{
+    memset(self, 0, sizeof(GdtEntry));
+
+    if (access == 0 && flags == 0)
+    {
+        return;
+    }
+
+    self->access = access | GDT_ACCESS_PRESENT | GDT_ACCESS_READ_WRITE | GDT_ACCESS_DESCRIPTOR;
+    self->flags = flags | GDT_FLAGS_GRANULARITY;
+
+    self->base_high = 0;
+    self->base_middle = 0;
+    self->base_low = 0;
+
+    self->limit_low = 0xffff;
+    self->limit_high = 0x0f;
+}
+
+void gdt_load_tss(Tss *tss)
+{
+    uintptr_t tss_ptr = (uintptr_t)tss;
+
+    spinlock_acquire(&lock);
+
+    gdt.tss_entry = (TssEntry){
+        .length = sizeof(TssEntry),
+
+        .base_low = tss_ptr & 0xffff,
+        .base_mid = (tss_ptr >> 16) & 0xff,
+        .base_high = (tss_ptr >> 24) & 0xff,
+        .base_upper = tss_ptr >> 32,
+
+        .flags1 = TSS_FLAGS_PRESENT | TSS_FLAGS_64BITS_AVAILABLE,
+        .flags2 = 0,
+
+        .reserved = 0,
+    };
+
+    spinlock_release(&lock);
+}
+
+uintptr_t gdt_descriptor(void)
+{
+    return (uintptr_t)&gdt_desc;
+}
+
+void gdt_init(void)
+{
+    gdt_lazy_init(&gdt.entries[GDT_NULL_DESC], 0, 0);
+
+    gdt_lazy_init(&gdt.entries[GDT_KERNEL_CODE], GDT_ACCESS_EXE, GDT_FLAGS_LONG_MODE);
+    gdt_lazy_init(&gdt.entries[GDT_KERNEL_DATA], 0, GDT_FLAGS_SIZE);
+
+    gdt_lazy_init(&gdt.entries[GDT_USER_DATA], GDT_ACCESS_USER, GDT_FLAGS_SIZE);
+    gdt_lazy_init(&gdt.entries[GDT_USER_CODE], GDT_ACCESS_USER | GDT_ACCESS_EXE, GDT_FLAGS_LONG_MODE);
+    gdt_load_tss(NULL);
+
+    gdt_flush(gdt_descriptor());
+    log$("GDT loaded");
+
+    tss_flush();
+    log$("TSS loaded");
+}

src/kernel/archs/x86_64/gdt.h

@@ -0,0 +1,91 @@
+#pragma once
+
+#include <res.h>
+#include <stdint.h>
+
+enum gdtaccess : uint8_t
+{
+    GDT_ACCESS_READ_WRITE = (1 << 1),
+    GDT_ACCESS_EXE = (1 << 3),
+    GDT_ACCESS_DESCRIPTOR = (1 << 4),
+    GDT_ACCESS_USER = (3 << 5),
+    GDT_ACCESS_PRESENT = (1 << 7),
+};
+
+enum gdtflags : uint8_t
+{
+    GDT_FLAGS_LONG_MODE = (1 << 1),
+    GDT_FLAGS_SIZE = (1 << 2),
+    GDT_FLAGS_GRANULARITY = (1 << 3),
+};
+
+enum tssflags : uint8_t
+{
+    TSS_FLAGS_PRESENT = (1 << 7),
+    TSS_FLAGS_64BITS_AVAILABLE = (0x9),
+};
+
+enum
+{
+    GDT_NULL_DESC,
+    GDT_KERNEL_CODE,
+    GDT_KERNEL_DATA,
+    GDT_USER_DATA,
+    GDT_USER_CODE,
+
+    GDT_ENTRIES_LENGTH
+};
+
+typedef struct [[gnu::packed]]
+{
+    uint16_t limit_low;
+    uint16_t base_low;
+    uint8_t base_middle;
+    uint8_t access;
+    uint8_t limit_high : 4;
+    uint8_t flags : 4;
+    uint8_t base_high;
+} GdtEntry;
+
+typedef struct [[gnu::packed]]
+{
+    uint16_t length;
+    uint16_t base_low;
+    uint8_t base_mid;
+    uint8_t flags1;
+    uint8_t flags2;
+    uint8_t base_high;
+    uint32_t base_upper;
+    uint32_t reserved;
+} TssEntry;
+
+typedef struct [[gnu::packed]]
+{
+    uint32_t reserved;
+    uint64_t rsp[3];
+    uint64_t reserved0;
+    uint64_t ist[7];
+    uint32_t reserved1;
+    uint32_t reserved2;
+    uint16_t reserved3;
+    uint16_t iopb_offset;
+} Tss;
+
+typedef struct [[gnu::packed]]
+{
+    uint16_t size;
+    uintptr_t offset;
+} GdtDescriptor;
+
+typedef struct [[gnu::packed]]
+{
+    GdtEntry entries[GDT_ENTRIES_LENGTH];
+    TssEntry tss_entry;
+} Gdt;
+
+void gdt_init(void);
+void gdt_load_tss(Tss *self);
+uintptr_t gdt_descriptor(void);
+
+extern void gdt_flush(uintptr_t);
+extern void tss_flush(void);

src/kernel/archs/x86_64/helper.s

@@ -0,0 +1,22 @@
+.globl gdt_flush
+.globl tss_flush
+
+gdt_flush:
+    lgdt (%rdi)
+    
+    mov $0x10, %ax
+    mov %ax, %ss
+    mov %ax, %ds
+    mov %ax, %es
+    pop %rdi
+
+    mov $0x08, %rax
+    push %rax
+    push %rdi
+    lretq
+
+
+tss_flush:
+    mov $0x28, %ax 
+    ltr %ax
+    ret

src/kernel/archs/x86_64/mod.c

@@ -1,6 +1,9 @@
+#include <hal.h>
 #include <io/stream.h>
+#include <res.h>
 
 #include "e9.h"
+#include "gdt.h"
 
 Stream hal_dbg_stream(void)
 {
@@ -9,6 +12,8 @@ Stream hal_dbg_stream(void)
     };
 }
 
-void hal_setup(void)
+Res hal_setup(void)
 {
+    gdt_init();
+    return ok$();
 }

src/kernel/core/main.c

@@ -1,8 +1,10 @@
 #include <dbg/log.h>
+#include <hal.h>
 
 _Noreturn int _start()
 {
     log$("Hello, world!");
+    hal_setup();
     for (;;)
         ;
 }