1/*
2 * Copyright (c) 2012 The Chromium Authors. All rights reserved.
3 * Use of this source code is governed by a BSD-style license that can be
4 * found in the LICENSE file.
5 */
6
7#include "native_client/src/include/elf32.h"
8#include "native_client/src/include/elf_auxv.h"
9#include "native_client/src/include/nacl_macros.h"
10#include "native_client/src/untrusted/nacl/nacl_startup.h"
11#include "ppapi/native_client/src/untrusted/pnacl_irt_shim/shim_ppapi.h"
12
13
14/*
15 * This is the true entry point for untrusted code.
16 * See nacl_startup.h for the layout at the argument pointer.
17 */
18void _pnacl_wrapper_start(uint32_t *info) {
19  Elf32_auxv_t *auxv = nacl_startup_auxv(info);
20
21  Elf32_auxv_t *entry = NULL;
22  for (Elf32_auxv_t *av = auxv; av->a_type != AT_NULL; ++av) {
23    if (av->a_type == AT_SYSINFO) {
24      entry = av;
25      break;
26    }
27  }
28
29  if (entry != NULL) {
30    /*
31     * Save the real irt interface query function.
32     */
33    __pnacl_real_irt_query_func = (TYPE_nacl_irt_query) entry->a_un.a_val;
34
35    /*
36     * Overwrite the auxv slot with the pnacl IRT shim query function.
37     */
38    entry->a_type = AT_SYSINFO;
39    entry->a_un.a_val = (uintptr_t) __pnacl_wrap_irt_query_func;
40  }
41
42  /* If entry is NULL still allow startup to continue.  It may be the case
43   * that the IRT was not actually used (e.g., for some commandline tests).
44   * For newlib, we can tell that the IRT isn't used when libnacl_sys_private.a
45   * is in the bitcode link line. However, glibc does not use
46   * libnacl_sys_private, so that would not work. We could look for -lppapi
47   * in the bitcode link line, but looking at the bitcode link line
48   * seems brittle (what if the bitcode link was separated from translation).
49   * Thus we always wrap _start, even if there is no IRT auxv entry.
50   */
51
52  /*
53   * Call the user entry point function.  It should not return.
54   * TODO(sehr): Find a way to ensure this is invoked via a tail call.
55   */
56  _start(info);
57}
58