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 "private/bionic_auxv.h"
43 #include "private/bionic_ssp.h"
44 #include "private/bionic_tls.h"
45 #include "private/KernelArgumentBlock.h"
46 #include "pthread_internal.h"
48 extern "C" abort_msg_t** __abort_message_ptr;
49 extern "C" uintptr_t __get_sp(void);
50 extern "C" int __system_properties_init(void);
51 extern "C" int __set_tls(void* ptr);
52 extern "C" int __set_tid_address(int* tid_address);
54 __LIBC_HIDDEN__ void __libc_init_vdso();
56 // Not public, but well-known in the BSDs.
57 const char* __progname;
59 // Declared in <unistd.h>.
60 char** environ;
62 // Declared in "private/bionic_ssp.h".
63 uintptr_t __stack_chk_guard = 0;
65 static size_t get_main_thread_stack_size() {
66 rlimit stack_limit;
67 int rlimit_result = getrlimit(RLIMIT_STACK, &stack_limit);
68 if ((rlimit_result == 0) &&
69 (stack_limit.rlim_cur != RLIM_INFINITY) &&
70 (stack_limit.rlim_cur > PTHREAD_STACK_MIN)) {
71 return (stack_limit.rlim_cur & ~(PAGE_SIZE - 1));
72 }
73 return PTHREAD_STACK_SIZE_DEFAULT;
74 }
76 /* Init TLS for the initial thread. Called by the linker _before_ libc is mapped
77 * in memory. Beware: all writes to libc globals from this function will
78 * apply to linker-private copies and will not be visible from libc later on.
79 *
80 * Note: this function creates a pthread_internal_t for the initial thread and
81 * stores the pointer in TLS, but does not add it to pthread's thread list. This
82 * has to be done later from libc itself (see __libc_init_common).
83 *
84 * This function also stores a pointer to the kernel argument block in a TLS slot to be
85 * picked up by the libc constructor.
86 */
87 void __libc_init_tls(KernelArgumentBlock& args) {
88 __libc_auxv = args.auxv;
90 static void* tls[BIONIC_TLS_SLOTS];
91 static pthread_internal_t main_thread;
92 main_thread.tls = tls;
94 // Tell the kernel to clear our tid field when we exit, so we're like any other pthread.
95 // As a side-effect, this tells us our pid (which is the same as the main thread's tid).
96 main_thread.tid = __set_tid_address(&main_thread.tid);
97 main_thread.set_cached_pid(main_thread.tid);
99 // Work out the extent of the main thread's stack.
100 uintptr_t stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
101 size_t stack_size = get_main_thread_stack_size();
102 void* stack_bottom = reinterpret_cast<void*>(stack_top - stack_size);
104 // We don't want to free the main thread's stack even when the main thread exits
105 // because things like environment variables with global scope live on it.
106 pthread_attr_init(&main_thread.attr);
107 pthread_attr_setstack(&main_thread.attr, stack_bottom, stack_size);
108 main_thread.attr.flags = PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK | PTHREAD_ATTR_FLAG_MAIN_THREAD;
110 __init_thread(&main_thread, false);
111 __init_tls(&main_thread);
112 __set_tls(main_thread.tls);
113 tls[TLS_SLOT_BIONIC_PREINIT] = &args;
115 __init_alternate_signal_stack(&main_thread);
116 }
118 void __libc_init_common(KernelArgumentBlock& args) {
119 // Initialize various globals.
120 environ = args.envp;
121 errno = 0;
122 __libc_auxv = args.auxv;
123 __progname = args.argv[0] ? args.argv[0] : "<unknown>";
124 __abort_message_ptr = args.abort_message_ptr;
126 // AT_RANDOM is a pointer to 16 bytes of randomness on the stack.
127 __stack_chk_guard = *reinterpret_cast<uintptr_t*>(getauxval(AT_RANDOM));
129 // Get the main thread from TLS and add it to the thread list.
130 pthread_internal_t* main_thread = __get_thread();
131 _pthread_internal_add(main_thread);
133 __system_properties_init(); // Requires 'environ'.
135 __libc_init_vdso();
136 }
138 /* This function will be called during normal program termination
139 * to run the destructors that are listed in the .fini_array section
140 * of the executable, if any.
141 *
142 * 'fini_array' points to a list of function addresses. The first
143 * entry in the list has value -1, the last one has value 0.
144 */
145 void __libc_fini(void* array) {
146 void** fini_array = reinterpret_cast<void**>(array);
147 const size_t minus1 = ~(size_t)0; /* ensure proper sign extension */
149 /* Sanity check - first entry must be -1 */
150 if (array == NULL || (size_t)fini_array[0] != minus1) {
151 return;
152 }
154 /* skip over it */
155 fini_array += 1;
157 /* Count the number of destructors. */
158 int count = 0;
159 while (fini_array[count] != NULL) {
160 ++count;
161 }
163 /* Now call each destructor in reverse order. */
164 while (count > 0) {
165 void (*func)() = (void (*)()) fini_array[--count];
167 /* Sanity check, any -1 in the list is ignored */
168 if ((size_t)func == minus1) {
169 continue;
170 }
172 func();
173 }
175 #ifndef LIBC_STATIC
176 {
177 extern void __libc_postfini(void) __attribute__((weak));
178 if (__libc_postfini) {
179 __libc_postfini();
180 }
181 }
182 #endif
183 }