setjmp.asm

gerneral os development

%include "asm.inc"

SECTION .text

EXP setjmp
	push ebx
		mov ebx,[8 + esp]

		mov [0 + ebx],edi	; buf->edi == 0(ebx) == EDI
		mov [4 + ebx],esi	; buf->esi == 4(ebx) == ESI
		mov [8 + ebx],ebp	; buf->ebp == 8(ebx) == EBP

		mov [20 + ebx],edx	; buf->edx == 20(ebx) == EDX
		mov [24 + ebx],ecx	; buf->ecx == 24(ebx) == ECX
		mov [28 + ebx],eax	; buf->eax == 28(ebx) == EAX

; use EBX value saved on stack; not the current value
		mov eax,[esp]
		mov [16 + ebx],eax	; buf->ebx == 16(ebx) == EBX

; use ESP value after RET; not the current value
		lea eax,[8 + esp]
		mov [12 + ebx],eax	; buf->esp == 32(ebx) == ESP

; use return address of this routine (EIP value saved on stack);
; not the current value
		mov eax,[4 + esp]
		mov [32 + ebx],eax	; buf->eip == 36(ebx) == EIP

; none of the PUSH or MOV instructions changed EFLAGS!
		pushf
		pop dword [36 + ebx]	; buf->eflags == 40(ebx) == EFLAGS
	pop ebx
	xor eax,eax
	ret