linux x86_64 system call using shellcode

system_call.c

// author: @hc0d3r
// license: wtfpl

#include <asm/unistd_64.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <stdio.h>

static const char syscall_sc[]=
	"\x48\x89\xf8"           // mov %rdi,%rax
	"\x48\x89\xf7"           // mov %rsi,%rdi
	"\x48\x89\xd6"           // mov %rdx,%rsi
	"\x48\x89\xca"           // mov %rcx,%rdx
	"\x4d\x89\xc2"           // mov %r8,%r10
	"\x4d\x89\xc8"           // mov %r9,%r8
	"\x4c\x8b\x4c\x24\x08"   // mov 0x8(%rsp),%r9
	"\x0f\x05"               // syscall
	"\xc3";                  // ret

#define x86_64_syscall(n, args...) ((long(*)(long, ...))(syscall_sc))(n, args)

int main(void){
	char msg[]="Mommy I know the System V ABI\n";

	x86_64_syscall(__NR_write, 1, msg, sizeof(msg)-1);

	void *map_addr = (void*)x86_64_syscall(__NR_mmap, 0x13370000, 4096, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
	printf("addr = %p\n", map_addr);

	int fd = x86_64_syscall(__NR_open, "/etc/issue", O_RDONLY);
	printf("fd = %d\n", fd);

	x86_64_syscall(__NR_close, fd);
	x86_64_syscall(__NR_munmap, map_addr, 4096);
	x86_64_syscall(__NR_exit, 5);
}