#include <unistd.h>
#include <errno.h>
#include "syscall.h"
#include "libc.h"
#include "pthread_impl.h"

struct ctx {
  int id, eid, sid;
  int nr, err;
};

static void do_setxid(void* p) {
  struct ctx* c = p;
  if (c->err > 0)
    return;
  int ret = -__syscall(c->nr, c->id, c->eid, c->sid);
  if (ret && !c->err) {
    /* If one thread fails to set ids after another has already
     * succeeded, forcibly killing the process is the only safe
     * thing to do. State is inconsistent and dangerous. Use
     * SIGKILL because it is uncatchable. */
    __block_all_sigs(0);
    __syscall(SYS_kill, __syscall(SYS_getpid), SIGKILL);
  }
  c->err = ret;
}

int __setxid(int nr, int id, int eid, int sid) {
  /* err is initially nonzero so that failure of the first thread does not
   * trigger the safety kill above. */
  struct ctx c = {.nr = nr, .id = id, .eid = eid, .sid = sid, .err = -1};
  __synccall(do_setxid, &c);
  if (c.err) {
    if (c.err > 0)
      errno = c.err;
    return -1;
  }
  return 0;
}