1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <android/api-level.h>
30 #include <elf.h>
31 #include <errno.h>
32 #include <stddef.h>
33 #include <stdint.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <sys/auxv.h>
37 #include <sys/mman.h>
38
39 #include "libc_init_common.h"
40 #include "pthread_internal.h"
41
42 #include "private/bionic_globals.h"
43 #include "private/bionic_page.h"
44 #include "private/bionic_tls.h"
45 #include "private/KernelArgumentBlock.h"
46
47 extern "C" int __cxa_atexit(void (*)(void *), void *, void *);
48
call_array(void (** list)())49 static void call_array(void(**list)()) {
50 // First element is -1, list is null-terminated
51 while (*++list) {
52 (*list)();
53 }
54 }
55
apply_gnu_relro()56 static void apply_gnu_relro() {
57 ElfW(Phdr)* phdr_start = reinterpret_cast<ElfW(Phdr)*>(getauxval(AT_PHDR));
58 unsigned long int phdr_ct = getauxval(AT_PHNUM);
59
60 for (ElfW(Phdr)* phdr = phdr_start; phdr < (phdr_start + phdr_ct); phdr++) {
61 if (phdr->p_type != PT_GNU_RELRO) {
62 continue;
63 }
64
65 ElfW(Addr) seg_page_start = PAGE_START(phdr->p_vaddr);
66 ElfW(Addr) seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz);
67
68 // Check return value here? What do we do if we fail?
69 mprotect(reinterpret_cast<void*>(seg_page_start), seg_page_end - seg_page_start, PROT_READ);
70 }
71 }
72
73 // The program startup function __libc_init() defined here is
74 // used for static executables only (i.e. those that don't depend
75 // on shared libraries). It is called from arch-$ARCH/bionic/crtbegin_static.S
76 // which is directly invoked by the kernel when the program is launched.
77 //
78 // The 'structors' parameter contains pointers to various initializer
79 // arrays that must be run before the program's 'main' routine is launched.
80
__libc_init(void * raw_args,void (* onexit)(void)__unused,int (* slingshot)(int,char **,char **),structors_array_t const * const structors)81 __noreturn void __libc_init(void* raw_args,
82 void (*onexit)(void) __unused,
83 int (*slingshot)(int, char**, char**),
84 structors_array_t const * const structors) {
85 KernelArgumentBlock args(raw_args);
86 __libc_init_main_thread(args);
87
88 // Initializing the globals requires TLS to be available for errno.
89 __init_thread_stack_guard(__get_thread());
90 __libc_init_globals(args);
91
92 __libc_init_AT_SECURE(args);
93 __libc_init_common(args);
94
95 apply_gnu_relro();
96
97 // Several Linux ABIs don't pass the onexit pointer, and the ones that
98 // do never use it. Therefore, we ignore it.
99
100 call_array(structors->preinit_array);
101 call_array(structors->init_array);
102
103 // The executable may have its own destructors listed in its .fini_array
104 // so we need to ensure that these are called when the program exits
105 // normally.
106 if (structors->fini_array != NULL) {
107 __cxa_atexit(__libc_fini,structors->fini_array,NULL);
108 }
109
110 exit(slingshot(args.argc, args.argv, args.envp));
111 }
112
bionic_get_application_target_sdk_version()113 uint32_t bionic_get_application_target_sdk_version() {
114 return __ANDROID_API__;
115 }
116