/* Copyright (c) 2014-2021, Michael Santos <michael.santos@gmail.com>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include "alcove.h"
#include "alcove_call.h"

#include "alcove_fork.h"

#include "alcove_clone_constants.h"

/*
 * clone(2)
 *
 */
ssize_t alcove_sys_clone(alcove_state_t *ap, const char *arg, size_t len,
                         char *reply, size_t rlen) {
#ifdef __linux__
  int index = 0;
  int rindex = 0;

  alcove_arg_t child_arg = {0};
  alcove_stdio_t fd = {0};
  struct rlimit stack_size = {0};
  char *child_stack;
  int flags = 0;
  pid_t pid;
  int errnum;
  sigset_t oldset;
  sigset_t set;

  if (ap->depth >= ap->maxforkdepth)
    return alcove_mk_errno(reply, rlen, EAGAIN);

  if (pid_foreach(ap, 0, NULL, NULL, pid_equal, avail_pid) != 0)
    return alcove_mk_errno(reply, rlen, EAGAIN);

  /* flags */
  switch (alcove_decode_constant_list(arg, len, &index, &flags,
                                      alcove_clone_constants)) {
  case 0:
    break;
  case 1:
    return alcove_mk_error(reply, rlen, "enotsup");
  default:
    return -1;
  }

  if (getrlimit(RLIMIT_STACK, &stack_size) < 0)
    return alcove_mk_errno(reply, rlen, errno);

  child_stack = calloc(stack_size.rlim_cur, 1);
  if (child_stack == NULL)
    return alcove_mk_errno(reply, rlen, errno);

  if (alcove_stdio(&fd) < 0)
    goto ERROR;

  (void)sigfillset(&set);
  (void)sigemptyset(&oldset);

  if (sigprocmask(SIG_BLOCK, &set, &oldset) < 0)
    goto ERROR;

  child_arg.ap = ap;
  child_arg.fd = &fd;
  child_arg.sigset = &oldset;

  pid = clone(alcove_child_fun, child_stack + stack_size.rlim_cur,
              flags | SIGCHLD, &child_arg);

  if (sigprocmask(SIG_SETMASK, &oldset, NULL) < 0)
    goto ERROR;

  if (pid < 0)
    goto ERROR;

  free(child_stack);

  if (alcove_parent_fd(ap, &fd, pid) < 0)
    return alcove_mk_errno(reply, rlen, errno);

  ALCOVE_OK(reply, rlen, &rindex,
            alcove_encode_long(reply, rlen, &rindex, pid));

  return rindex;

ERROR:
  errnum = errno;
  free(child_stack);
  return alcove_mk_errno(reply, rlen, errnum);
#else
  UNUSED(ap);
  UNUSED(arg);
  UNUSED(len);

  return alcove_mk_atom(reply, rlen, "undef");
#endif
}