X86 Assembly cheatsheet¶
Exit¶
# gcc -o a.out -nostdlib a.s
.global _start
.section .text
_start:
mov $0x1,%eax # 32 bit of exit is 1
mov $0x1,%ebx
int $0x80
.section .data
Note that int 0x80 always invokes 32-bit system calls. To use system calls
define on X64 systems, we need to use syscall instruction.
.global _start
.section .text
_start:
mov $0x3c,%eax # 64 bit of exit is 60(0x3c)
mov $0x1,%ebx
syscall
.section .data
Hello Word¶
# gcc -o a.out -nostdlib a.s
# ./a.out
# Hello World
.global _start
.section .text
_start:
# write(stdout, "Hello World", 13);
mov $0x4,%eax # 32 bit write syscall number
mov $0x1,%ebx # unsigned int fd (stdout)
lea (message),%ecx # const char *buf
mov $13,%edx # size_t count
int $0x80
# exit(0)
mov $0x1,%eax
mov $0x0,%ebx
int $0x80
.section .data
message:
.ascii "Hello World\n"
do while¶
.global _start
.section .text
_start:
mov $0x1,%rsi
loop: # do {
# write(stdout, "Hello World\n", 13)
mov $0x4,%eax
mov $0x1,%ebx
lea (message),%ecx
mov $13,%edx
int $0x80
add $0x1,%rsi
cmp $0x5,%rsi
jbe loop # } while(i<=5)
# exit
mov $0x1,%eax
mov $0x0,%ebx
int $0x80
.section .data
message: .ascii "Hello World\n"
Procedures¶
.global _start
.section .text
_start:
callq print
# exit
mov $0x1,%eax
mov $0x0,%ebx
int $0x80
print:
# write(stdout, "Hello World\n", 13)
mov $0x4,%eax
mov $0x1,%ebx
lea (message),%ecx
mov $13,%edx
int $0x80
ret
.section .data
message: .ascii "Hello World\n"
