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