1 files changed, 84 insertions, 0 deletions
diff --git a/stage1/stage1.S b/stage1/stage1.S
new file mode 100644
index 0000000..e11e36b
--- /dev/null
+++ b/stage1/stage1.S
@@ -0,0 +1,84 @@
+.intel_syntax noprefix
+.code16
+
+.extern _stack_start
+.extern _stack_end
+
+.global stage1_sector
+
+.section .stage1, "ax"
+
+stage1_sector:
+	xor ax, ax
+	
+	mov ah, 0x0e
+	mov al, 'C'
+	mov bh, 0x0
+	mov bl, 0x0
+
+	int 0x10
+	
+	cli
+
+	lgdt gdtr
+	
+	mov eax, cr0
+	or eax, (1 << 0)
+	mov cr0, eax
+
+	jmp 0x8:_32_start
+	
+	cli
+	hlt
+
+.code32
+_32_start:
+	mov eax, 0x10
+
+	mov ds, ax
+	mov ss, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	
+	jmp 0x8:_32_entry
+
+	cli
+	hlt
+	
+_32_entry:
+	mov eax, offset _stack_start
+	mov ebp, eax
+	mov eax, offset _stack_end
+	mov esp, eax 
+
+	call centry
+
+	cli
+	hlt
+
+.code16
+.section .stage1_ro, "aw"
+
+gdt:
+	.quad 0x0 // Null seg
+	
+	.word 0xFFFF // Code seg
+	.word 0x0000
+	.byte 0x0
+	.byte 0b10011011 // A=1 RW=1 DC=0 E=1 S=1 DPL=00 P=1
+	.byte 0b11001111
+	.byte 0x0000
+
+	.word 0xFFFF // Data Seg
+	.word 0x0000
+	.byte 0x0
+	.byte 0b10010011 // A=1 RW=1 DC=0 E=0 S=1 DPL=00 P=1
+	.byte 0b11001111
+	.byte 0x0000
+
+end_gdt:
+
+gdtr:
+	.word end_gdt - gdt - 1
+	.long gdt