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 */
29 #include "libc_init_common.h"
31 #include <elf.h>
32 #include <errno.h>
33 #include <stddef.h>
34 #include <stdint.h>
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include <sys/auxv.h>
38 #include <sys/time.h>
39 #include <sys/resource.h>
40 #include <unistd.h>
42 #include "atexit.h"
43 #include "private/bionic_auxv.h"
44 #include "private/bionic_ssp.h"
45 #include "private/bionic_tls.h"
46 #include "private/KernelArgumentBlock.h"
47 #include "pthread_internal.h"
49 extern "C" abort_msg_t** __abort_message_ptr;
50 extern "C" uintptr_t __get_sp(void);
51 extern "C" int __system_properties_init(void);
52 extern "C" int __set_tls(void* ptr);
53 extern "C" int __set_tid_address(int* tid_address);
55 // Not public, but well-known in the BSDs.
56 const char* __progname;
58 // Declared in <unistd.h>.
59 char** environ;
61 // Declared in "private/bionic_ssp.h".
62 uintptr_t __stack_chk_guard = 0;
64 static size_t get_main_thread_stack_size() {
65 rlimit stack_limit;
66 int rlimit_result = getrlimit(RLIMIT_STACK, &stack_limit);
67 if ((rlimit_result == 0) &&
68 (stack_limit.rlim_cur != RLIM_INFINITY) &&
69 (stack_limit.rlim_cur > PTHREAD_STACK_MIN)) {
70 return (stack_limit.rlim_cur & ~(PAGE_SIZE - 1));
71 }
72 return PTHREAD_STACK_SIZE_DEFAULT;
73 }
75 /* Init TLS for the initial thread. Called by the linker _before_ libc is mapped
76 * in memory. Beware: all writes to libc globals from this function will
77 * apply to linker-private copies and will not be visible from libc later on.
78 *
79 * Note: this function creates a pthread_internal_t for the initial thread and
80 * stores the pointer in TLS, but does not add it to pthread's gThreadList. This
81 * has to be done later from libc itself (see __libc_init_common).
82 *
83 * This function also stores a pointer to the kernel argument block in a TLS slot to be
84 * picked up by the libc constructor.
85 */
86 void __libc_init_tls(KernelArgumentBlock& args) {
87 __libc_auxv = args.auxv;
89 uintptr_t stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
90 size_t stack_size = get_main_thread_stack_size();
91 uintptr_t stack_bottom = stack_top - stack_size;
93 static void* tls[BIONIC_TLS_SLOTS];
94 static pthread_internal_t main_thread;
95 main_thread.tls = tls;
97 // Tell the kernel to clear our tid field when we exit, so we're like any other pthread.
98 main_thread.tid = __set_tid_address(&main_thread.tid);
100 // We already have a stack, and we don't want to free it up on exit (because things like
101 // environment variables with global scope live on it).
102 pthread_attr_init(&main_thread.attr);
103 pthread_attr_setstack(&main_thread.attr, (void*) stack_bottom, stack_size);
104 main_thread.attr.flags = PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK | PTHREAD_ATTR_FLAG_MAIN_THREAD;
106 __init_thread(&main_thread, false);
107 __init_tls(&main_thread);
108 __set_tls(main_thread.tls);
109 tls[TLS_SLOT_BIONIC_PREINIT] = &args;
111 __init_alternate_signal_stack(&main_thread);
112 }
114 void __libc_init_common(KernelArgumentBlock& args) {
115 // Initialize various globals.
116 environ = args.envp;
117 errno = 0;
118 __libc_auxv = args.auxv;
119 __progname = args.argv[0] ? args.argv[0] : "<unknown>";
120 __abort_message_ptr = args.abort_message_ptr;
122 // AT_RANDOM is a pointer to 16 bytes of randomness on the stack.
123 __stack_chk_guard = *reinterpret_cast<uintptr_t*>(getauxval(AT_RANDOM));
125 // Get the main thread from TLS and add it to the thread list.
126 pthread_internal_t* main_thread = __get_thread();
127 _pthread_internal_add(main_thread);
129 __system_properties_init(); // Requires 'environ'.
130 }
132 /* This function will be called during normal program termination
133 * to run the destructors that are listed in the .fini_array section
134 * of the executable, if any.
135 *
136 * 'fini_array' points to a list of function addresses. The first
137 * entry in the list has value -1, the last one has value 0.
138 */
139 void __libc_fini(void* array) {
140 void** fini_array = reinterpret_cast<void**>(array);
141 const size_t minus1 = ~(size_t)0; /* ensure proper sign extension */
143 /* Sanity check - first entry must be -1 */
144 if (array == NULL || (size_t)fini_array[0] != minus1) {
145 return;
146 }
148 /* skip over it */
149 fini_array += 1;
151 /* Count the number of destructors. */
152 int count = 0;
153 while (fini_array[count] != NULL) {
154 ++count;
155 }
157 /* Now call each destructor in reverse order. */
158 while (count > 0) {
159 void (*func)() = (void (*)()) fini_array[--count];
161 /* Sanity check, any -1 in the list is ignored */
162 if ((size_t)func == minus1) {
163 continue;
164 }
166 func();
167 }
169 #ifndef LIBC_STATIC
170 {
171 extern void __libc_postfini(void) __attribute__((weak));
172 if (__libc_postfini) {
173 __libc_postfini();
174 }
175 }
176 #endif
177 }