1 files changed, 40 insertions, 0 deletions
diff --git a/src/boot/stage2_switch_mode.asm b/src/boot/stage2_switch_mode.asm
new file mode 100644
index 0000000..9259e08
--- /dev/null
+++ b/src/boot/stage2_switch_mode.asm
@@ -0,0 +1,40 @@
+[bits 16]
+
+%include "boot/boot_gdt.asm"
+
+switch_to_protected_mode:
+	; switch off interrupts for now, we don't
+	; have a valid IDT installed yet
+	cli
+	
+	; load GDT (global descriptor table)
+	lgdt [gdt_descriptor]
+	
+	; do the actual switch
+	mov eax, cr0
+	or eax, 0x1
+	mov cr0, eax
+	
+	; unconditional far jump into code segment,
+	; wipes the instruction prefetch pipeline
+	jmp CODE_SEGMENT:init_pm
+	
+[bits 32]
+
+; initialize registers and stack for protected mode
+init_pm:
+	mov ax, DATA_SEGMENT
+	mov ds, ax
+	mov ss, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	
+	; a new stack
+	mov ebp, 0x90000
+	mov esp, ebp
+	
+	call BEGIN_PROTECTED_MODE
+	
+[bits 16]
+