unicorn/tests/regress/x86_self_modifying.s

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# Assembly instructions (tested on ubuntu 16.04 x86_64):
# $ as --32 x86_self_modifying.s -o x86_self_modifying.o
# $ ld -melf_i386 -z execstack x86_self_modifying.o -o x86_self_modifying.elf
# Test that it works. return code should be 65
# $ ./x86_self_modifying.elf
# $ echo $?
# 65
# Fix the entry point address in x86_self_modifying.py
# $ readelf -h x86_self_modifying.elf | grep Entry
# Entry point address: 0x8048074
.intel_syntax noprefix
.global _start
_start:
mov ebp, esp
sub ebp, 0x4000
mov edx, ebp
lea esi, [self_modifying]
mov edi, ebp
mov ecx, 0x2d
call memcpy
add ebp, 0x2d
xor ebx, ebx
call edx
mov eax, 1
int 0x80
memcpy:
cmp ecx, 0
je _end
dec ecx
mov al, byte ptr [esi+ecx]
mov byte ptr [edi+ecx], al
jmp memcpy
_end:
ret
self_modifying:
inc ebx
call $+5
pop esi
dec byte ptr [esi+11]
xor edx, edx
sub esi, 6
_loop_start:
cmp edx, 5
jz _loop_end
mov edi, ebp
mov ecx, 0x2d
lea eax, [memcpy]
call eax
inc edx
add ebp, 0x2d
mov byte ptr [ebp], 0xc3
jmp _loop_start
_loop_end: