Load GDT

kernel/src/gdt.rs

@@ -1 +1,72 @@
-pub fn setup_gdt() {}
+use core::{arch::asm, mem::size_of};
+
+#[repr(C)]
+struct GDTEntry {
+    limit_low: u16,
+    base_low: u16,
+    base_middle: u8,
+    access: u8,
+    flags: u8,
+    base_high: u8,
+}
+#[repr(C)]
+struct GDT {
+    entries: [GDTEntry; 3],
+}
+
+#[repr(C, packed)]
+struct GDTDescriptor {
+    limit: u16,
+    base: u64,
+}
+
+const GDT: GDT = GDT {
+    entries: [
+        GDTEntry {
+            limit_low: 0,
+            base_low: 0,
+            base_middle: 0,
+            access: 0,
+            flags: 0,
+            base_high: 0,
+        },
+        GDTEntry {
+            limit_low: 0,
+            base_low: 0,
+            base_middle: 0,
+            access: 0x9a,
+            flags: 0x20,
+            base_high: 0,
+        },
+        GDTEntry {
+            limit_low: 0,
+            base_low: 0,
+            base_middle: 0,
+            access: 0x92,
+            flags: 0,
+            base_high: 0,
+        },
+    ],
+};
+
+pub fn setup_gdt() {
+    let gdt_descriptor = GDTDescriptor {
+        limit: (size_of::<GDT>() - 1) as u16,
+        base: GDT.entries.as_ptr() as u64,
+    };
+    unsafe {
+        asm!("
+            lgdt ({})
+            push $8
+            push $1f
+            lretq
+            1:
+            mov $0x10, %ax
+            mov %ax, %ds
+            mov %ax, %es
+            mov %ax, %fs
+            mov %ax, %gs
+            mov %ax, %ss
+        ", in(reg) &gdt_descriptor, out("rax") _, options(att_syntax));
+    }
+}

loader/src/paging.rs

@@ -21,8 +21,7 @@ bitfield! {
     address, set_address: 63, 12;
 }
 
-#[repr(C)]
-#[repr(align(0x1000))]
+#[repr(C, align(0x1000))]
 struct PageTable {
     entries: [PageEntry; 512],
 }