GNU as x86サンプル

はじめに

先ずCのアセンブリ出力を参考にし、x64版とx86版を作る。

環境

• Windows 11 Pro (64bit)
• WSL (Ubuntu 22.04)

gcc

x86用のコンパイルには追加のインストールが必要。
Ubuntuの場合

$ sudo apt install libc6-dev-i386

fig1.c

// cc -m32 -o fig1 fig1.c
// cc -m32 -masm=intel -S -fno-asynchronous-unwind-tables fig1.c
#include <unistd.h>

int main(void)
{
	write(1, "hello\n", 6);
}

GNU as x64

fig2.asm

# Assembly (as, x64, Linux)
# as -o fig2.o fig2.asm
# ld -o fig2 fig2.o

	.intel_syntax noprefix

	.section .rodata
_msg:	.ascii	"hello, world\n"
	.equ	_len, ($ - _msg)

	.text
	.global _start
_start:
	mov	edx, _len
	lea	rsi, _msg
	mov	edi, 1		# stdout
	mov	eax, 1		# write
	syscall

	xor	edi, edi
	mov	eax, 60		# exit
	syscall

GNU as x86

fig3.asm

# as --32 -o fig3.o fig3.asm
# ld -m elf_i386 -o fig3 fig3.o

	.intel_syntax noprefix

	.section .rodata
_msg:	.ascii	"hello, world\n"
	.equ	_len, ($ - _msg)

	.text
	.global _start
_start:
	mov	edx, _len
	lea	ecx, _msg
	mov	ebx, 1		# stdout
	mov	eax, 4		# write
	int	0x80

	xor	ebx, ebx
	mov	eax, 1		# exit
	int	0x80

$ file fig3
fig3: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), statically linked, not stripped