/* Copyright (c) 2014-2020, 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"

#ifdef __linux__
#include <sys/prctl.h>
#ifdef HAVE_PRCTL_SECCOMP
#include <linux/seccomp.h>
#endif
#endif

#include "alcove_prctl_constants.h"

typedef struct {
  u_char type;
  unsigned long arg;
  char data[MAXMSGLEN];
  size_t len;
} alcove_prctl_arg_t;

enum { ALCOVE_PRARG_UNSIGNED_LONG, ALCOVE_PRARG_CSTRUCT, ALCOVE_PRARG_BINARY };

#define PRARG(x) (((x).type) ? (unsigned long)(x).data : (x).arg)

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

  int option = 0;
  alcove_alloc_t *elem[4] = {0};
  ssize_t nelem[4] = {0};
  int i = 0;

  alcove_prctl_arg_t prarg[4] = {0};

  int rv = 0;

  UNUSED(ap);

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

  /* arg2, arg3, arg4, arg5 */
  for (i = 0; i < 4; i++) {
    if (alcove_get_type(arg, len, &index, &type, &arity) < 0)
      return -1;

    switch (type) {
    case ERL_SMALL_INTEGER_EXT:
    case ERL_INTEGER_EXT:
      if (alcove_decode_ulong(arg, len, &index, &prarg[i].arg) < 0)
        return -1;

      break;

    case ERL_ATOM_EXT: {
      char define[MAXATOMLEN] = {0};
      long long val = 0;
      unsigned long constant = 0;

      if (alcove_decode_atom(arg, len, &index, define) < 0)
        return -1;

      if (alcove_lookup_constant(define, &val, alcove_prctl_constants) < 0)
        return alcove_mk_error(reply, rlen, "enotsup");

      if (val < 0 || val > INT32_MAX)
        return -1;

      constant = val;

      prarg[i].arg = constant;
    }

    break;

    case ERL_LIST_EXT:
      prarg[i].type = ALCOVE_PRARG_CSTRUCT;
      prarg[i].len = sizeof(prarg[i].data);
      if (alcove_decode_cstruct(arg, len, &index, prarg[i].data,
                                &(prarg[i].len), &(elem[i]), &(nelem[i])) < 0)
        return -1;

      break;

    case ERL_BINARY_EXT:
      prarg[i].type = ALCOVE_PRARG_BINARY;
      if (arity > sizeof(prarg[i].data))
        return -1;
      if (alcove_decode_binary(arg, len, &index, prarg[i].data,
                               &(prarg[i].len)) < 0)
        return -1;

      break;

    case ERL_NIL_EXT:
      if (alcove_decode_list_header(arg, len, &index, &arity) < 0 || arity != 0)
        return -1;

      break;

    default:
      return -1;
    }
  }

  rv = prctl(option, PRARG(prarg[0]), PRARG(prarg[1]), PRARG(prarg[2]),
             PRARG(prarg[3]));

  if (rv < 0)
    return alcove_mk_errno(reply, rlen, errno);

  ALCOVE_ERR(alcove_encode_version(reply, rlen, &rindex));
  ALCOVE_ERR(alcove_encode_tuple_header(reply, rlen, &rindex, 6));
  ALCOVE_ERR(alcove_encode_atom(reply, rlen, &rindex, "ok"));
  ALCOVE_ERR(alcove_encode_long(reply, rlen, &rindex, rv));

  for (i = 0; i < 4; i++) {
    switch (prarg[i].type) {
    case ALCOVE_PRARG_UNSIGNED_LONG:
      ALCOVE_ERR(alcove_encode_ulonglong(reply, rlen, &rindex, prarg[i].arg));
      break;
    case ALCOVE_PRARG_CSTRUCT:
      ALCOVE_ERR(alcove_encode_cstruct(reply, rlen, &rindex, prarg[i].data,
                                       prarg[i].len, elem[i], nelem[i]));
      break;
    case ALCOVE_PRARG_BINARY:
      ALCOVE_ERR(alcove_encode_binary(reply, rlen, &rindex, prarg[i].data,
                                      prarg[i].len));
      break;
    default:
      return -1;
    }
  }

  return rindex;
#else
  UNUSED(ap);
  UNUSED(arg);
  UNUSED(len);

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