My test program.

gistfile1.c

#include <sys/param.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/mman.h>
#include <sys/namei.h>
#include <sys/ucred.h>
#include <sys/queue.h>
#include <sys/vnode.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <vm/uma.h>

#include <sys/types.h>
#include <sys/socket.h> /* for AF_INET, AF_LOCAL */

#include <sys/mac.h>

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>

int main() {
  uint64_t buf[2] = {1, 0};
  int err;
  mac_t init;

  uint64_t *buf2 = (uint64_t*)malloc(sizeof(uint64_t)*2);

  buf2[0] = 1;
  buf2[1] = 0;

  printf("syscall: %d\n", mac_syscall("shill", 1, buf2));
  printf("real error num %d\n", errno);
  perror("foo");

  if (0 != (err = mac_from_text(&init, "shill/init")))
    return err;

  printf("set_proc: %d\n", mac_set_proc(init));

  printf("syscall: %d\n", mac_syscall("shill", 1, buf2));
  printf("real error num %d\n", errno);
  perror("foo");
  return 0;
}