/* Copyright (c) 2016-2017, 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"

#if defined(__linux__)
#include <sys/ptrace.h>
#ifndef PTRACE_TRACEME
#include <linux/ptrace.h>
#endif
#include "alcove_ptrace_constants.h"

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

enum {
  ALCOVE_PTRACEARG_INT,
  ALCOVE_PTRACEARG_CSTRUCT,
  ALCOVE_PTRACEARG_BINARY
};
#endif

#define PRTRACEARG(x) (((x).type) ? (x).data : (void *)(x).arg)

/*
 * ptrace(2)
 *
 */
ssize_t alcove_sys_ptrace(alcove_state_t *ap, const char *arg, size_t len,
                          char *reply, size_t rlen) {
#if defined(__linux__)
  int index = 0;
  int rindex = 0;
  int type = 0;
  int arity = 0;

  int request = 0;
  pid_t pid = 0;
  alcove_ptrace_arg_t addr = {0};
  alcove_ptrace_arg_t data = {0};
  alcove_alloc_t *elem = NULL;
  ssize_t nelem = 0;

  long rv = 0;

  UNUSED(ap);

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

  /* pid */
  if (alcove_decode_int(arg, len, &index, &pid) < 0)
    return -1;

  /* addr */
  if (alcove_get_type(arg, len, &index, &type, &arity) < 0)
    return -1;

  switch (type) {
  case ERL_SMALL_INTEGER_EXT:
  case ERL_INTEGER_EXT:
    addr.type = ALCOVE_PTRACEARG_INT;
    if (alcove_decode_ulong(arg, len, &index, &addr.arg) < 0)
      return -1;

    break;

  case ERL_LIST_EXT:
    addr.type = ALCOVE_PTRACEARG_CSTRUCT;
    addr.len = sizeof(addr.data);
    if (alcove_decode_cstruct(arg, len, &index, addr.data, &(addr.len), &elem,
                              &nelem) < 0)
      return -1;

    break;

  case ERL_BINARY_EXT:
    addr.type = ALCOVE_PTRACEARG_BINARY;
    if (arity > sizeof(addr.data))
      return -1;
    if (alcove_decode_binary(arg, len, &index, addr.data, &addr.len) < 0)
      return -1;

    break;

  default:
    return -1;
  }

  /* data */
  if (alcove_get_type(arg, len, &index, &type, &arity) < 0)
    return -1;

  switch (type) {
  case ERL_SMALL_INTEGER_EXT:
  case ERL_INTEGER_EXT:
    data.type = ALCOVE_PTRACEARG_INT;
    if (alcove_decode_ulong(arg, len, &index, &data.arg) < 0)
      return -1;

    break;

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

    break;

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

    break;

  default:
    return -1;
  }

  errno = 0;
  rv = ptrace(request, pid, PRTRACEARG(addr), PRTRACEARG(data));

  if (errno)
    return alcove_mk_errno(reply, rlen, errno);

  ALCOVE_ERR(alcove_encode_version(reply, rlen, &rindex));
  ALCOVE_ERR(alcove_encode_tuple_header(reply, rlen, &rindex, 4));
  ALCOVE_ERR(alcove_encode_atom(reply, rlen, &rindex, "ok"));
  ALCOVE_ERR(alcove_encode_long(reply, rlen, &rindex, rv));

  switch (addr.type) {
  case ALCOVE_PTRACEARG_CSTRUCT:
    ALCOVE_ERR(alcove_encode_cstruct(reply, rlen, &rindex, addr.data, addr.len,
                                     elem, nelem));
    break;
  case ALCOVE_PTRACEARG_INT: /* return an empty binary */
  case ALCOVE_PTRACEARG_BINARY:
    ALCOVE_ERR(alcove_encode_binary(reply, rlen, &rindex, addr.data, addr.len));
    break;
  default:
    return -1;
  }

  switch (data.type) {
  case ALCOVE_PTRACEARG_CSTRUCT:
    ALCOVE_ERR(alcove_encode_cstruct(reply, rlen, &rindex, data.data, data.len,
                                     elem, nelem));
    break;
  case ALCOVE_PTRACEARG_INT: /* return an empty binary */
  case ALCOVE_PTRACEARG_BINARY:
    ALCOVE_ERR(alcove_encode_binary(reply, rlen, &rindex, data.data, data.len));
    break;
  default:
    return -1;
  }

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

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