1 files changed, 72 insertions, 0 deletions
diff --git a/src/arch/amd64/boot.S b/src/arch/amd64/boot.S
index e69de29..f7c24c4 100644
--- a/src/arch/amd64/boot.S
+++ b/src/arch/amd64/boot.S
@@ -0,0 +1,72 @@
+global start
+extern kmain
+bits 32
+
+; base, limit, access, flags
+%macro gdt_entry 4
+	db %2 & 0xff
+	db (%2 >> 8) & 0xff
+	db %1 & 0xff
+	db (%1 >> 8) & 0xff
+	db (%1 >> 16) & 0xff
+	db %3
+	db ((%2 >> 16) & 0x0f) | (%4 << 4)
+	db (%1 >> 24) & 0xff
+%endmacro
+
+section .multiboot
+align 8
+mb_start:
+; header
+dd 0xe85250d6
+dd 0
+dd mb_end - mb_start
+dd 0x100000000 - (0xe85250d6 + (mb_end - mb_start))
+; null tag
+dw 0
+dw 0
+dd 8
+;
+mb_end:
+
+section .bss
+align 16
+stack_start:
+	resb 16384
+stack_end:
+
+section .rodata
+align 16
+gdt_start:
+gdt_entry 0, 0, 0, 0
+gdt_entry 0, 0xFFFFF, 0x9A, 0xC
+gdt_entry 0, 0xFFFFF, 0x92, 0xC
+gdt_end:
+gdt_descriptor:
+	dw gdt_end - gdt_start - 1
+	dd gdt_start
+
+
+section .text
+align 8
+start:
+	cli
+	lgdt [gdt_descriptor]
+	jmp 0x08:after_lgdt
+after_lgdt:
+	mov ax, 0x10
+	mov ds, ax
+	mov ss, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	mov esp, stack_end
+	mov ebp, stack_end
+	sti
+	push ebx
+	call kmain
+	cli
+halt:
+	hlt
+	jmp halt
+