noptest.c

#include <stdio.h>
#include <string.h>
#include <sys/mman.h>

int main(int argc, char **argv) {
    unsigned char bytes[] = {
        0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0xf3, 0x90, // rep*14 nop
        0xc3 // ret
    };
    unsigned char *code = (unsigned char *) mmap(NULL, 0x1000, PROT_READ|PROT_WRITE|PROT_EXEC,
            MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
    printf("Code mapped at %p\n", code);
    memcpy(code, bytes, 16);
    ((void (*)(void))code)();
    return 0;
}