| static | |
| long long os_write(long long fd, void *buf, long long len) { | |
| register long long x0 __asm__("x0") = fd; | |
| register long long x1 __asm__("x1") = (long long)buf; | |
| register long long x2 __asm__("x2") = len; | |
| register long long x8 __asm__("x8") = 64; | |
| __asm__ volatile ( | |
| "svc 0" | |
| : "+r"(x0) | |
| : "r"(x1), "r"(x2), "r"(x8) | |
| ); | |
| return x0; | |
| } | |
| static | |
| void | |
| os_exit(long long n) { | |
| register long long x0 __asm__("x0") = n; | |
| register long long x8 __asm__("x8") = 93; | |
| __asm__ volatile ( | |
| "svc 0" | |
| : | |
| : "r"(x0), "r"(x8) | |
| ); | |
| __builtin_unreachable(); | |
| } | |
| void _start(void) { | |
| char msg[] = "Hi\n"; | |
| long long n = os_write(2, msg, sizeof(msg)-1); | |
| os_exit(n); | |
| __builtin_unreachable(); | |
| } |
make CFLAGS=-nostdlib\ -static\ -O2 34-asm
I suffered from finding the program that the optimizer will never ruin my code.
static long long
os_write(long long fd, void *buf, long long len) {
__asm__ volatile (
"mov x8,64\n"
"svc 0\n"
"ret\n"
);
__builtin_unreachable();
}__asm__ (
".globl os_write\n"
"os_write:\n"
"mov x8,64\n"
"svc 0\n"
"ret\n"
);