libc_init_common.cpp revision 38778e3b6c89689bbdd01f4a52ac88f02bf59783 
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 "libc_init_common.h"
30
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>
41
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"
47
48extern "C" abort_msg_t** __abort_message_ptr;
49extern "C" uintptr_t __get_sp(void);
50extern "C" int __system_properties_init(void);
51extern "C" int __set_tls(void* ptr);
52extern "C" int __set_tid_address(int* tid_address);
53
54// Not public, but well-known in the BSDs.
55const char* __progname;
56
57// Declared in <unistd.h>.
58char** environ;
59
60// Declared in "private/bionic_ssp.h".
61uintptr_t __stack_chk_guard = 0;
62
63static size_t get_main_thread_stack_size() {
64  rlimit stack_limit;
65  int rlimit_result = getrlimit(RLIMIT_STACK, &stack_limit);
66  if ((rlimit_result == 0) &&
67      (stack_limit.rlim_cur != RLIM_INFINITY) &&
68      (stack_limit.rlim_cur > PTHREAD_STACK_MIN)) {
69    return (stack_limit.rlim_cur & ~(PAGE_SIZE - 1));
70  }
71  return PTHREAD_STACK_SIZE_DEFAULT;
72}
73
74/* Init TLS for the initial thread. Called by the linker _before_ libc is mapped
75 * in memory. Beware: all writes to libc globals from this function will
76 * apply to linker-private copies and will not be visible from libc later on.
77 *
78 * Note: this function creates a pthread_internal_t for the initial thread and
79 * stores the pointer in TLS, but does not add it to pthread's thread list. This
80 * has to be done later from libc itself (see __libc_init_common).
81 *
82 * This function also stores a pointer to the kernel argument block in a TLS slot to be
83 * picked up by the libc constructor.
84 */
85void __libc_init_tls(KernelArgumentBlock& args) {
86  __libc_auxv = args.auxv;
87
88  static void* tls[BIONIC_TLS_SLOTS];
89  static pthread_internal_t main_thread;
90  main_thread.tls = tls;
91
92  // Tell the kernel to clear our tid field when we exit, so we're like any other pthread.
93  // As a side-effect, this tells us our pid (which is the same as the main thread's tid).
94  main_thread.tid = __set_tid_address(&main_thread.tid);
95  main_thread.set_cached_pid(main_thread.tid);
96
97  // Work out the extent of the main thread's stack.
98  uintptr_t stack_top = (__get_sp() & ~(PAGE_SIZE - 1)) + PAGE_SIZE;
99  size_t stack_size = get_main_thread_stack_size();
100  void* stack_bottom = reinterpret_cast<void*>(stack_top - stack_size);
101
102  // We don't want to free the main thread's stack even when the main thread exits
103  // because things like environment variables with global scope live on it.
104  pthread_attr_init(&main_thread.attr);
105  pthread_attr_setstack(&main_thread.attr, stack_bottom, stack_size);
106  main_thread.attr.flags = PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK | PTHREAD_ATTR_FLAG_MAIN_THREAD;
107
108  __init_thread(&main_thread, false);
109  __init_tls(&main_thread);
110  __set_tls(main_thread.tls);
111  tls[TLS_SLOT_BIONIC_PREINIT] = &args;
112
113  __init_alternate_signal_stack(&main_thread);
114}
115
116void __libc_init_common(KernelArgumentBlock& args) {
117  // Initialize various globals.
118  environ = args.envp;
119  errno = 0;
120  __libc_auxv = args.auxv;
121  __progname = args.argv[0] ? args.argv[0] : "<unknown>";
122  __abort_message_ptr = args.abort_message_ptr;
123
124  // AT_RANDOM is a pointer to 16 bytes of randomness on the stack.
125  __stack_chk_guard = *reinterpret_cast<uintptr_t*>(getauxval(AT_RANDOM));
126
127  // Get the main thread from TLS and add it to the thread list.
128  pthread_internal_t* main_thread = __get_thread();
129  _pthread_internal_add(main_thread);
130
131  __system_properties_init(); // Requires 'environ'.
132}
133
134/* This function will be called during normal program termination
135 * to run the destructors that are listed in the .fini_array section
136 * of the executable, if any.
137 *
138 * 'fini_array' points to a list of function addresses. The first
139 * entry in the list has value -1, the last one has value 0.
140 */
141void __libc_fini(void* array) {
142  void** fini_array = reinterpret_cast<void**>(array);
143  const size_t minus1 = ~(size_t)0; /* ensure proper sign extension */
144
145  /* Sanity check - first entry must be -1 */
146  if (array == NULL || (size_t)fini_array[0] != minus1) {
147    return;
148  }
149
150  /* skip over it */
151  fini_array += 1;
152
153  /* Count the number of destructors. */
154  int count = 0;
155  while (fini_array[count] != NULL) {
156    ++count;
157  }
158
159  /* Now call each destructor in reverse order. */
160  while (count > 0) {
161    void (*func)() = (void (*)()) fini_array[--count];
162
163    /* Sanity check, any -1 in the list is ignored */
164    if ((size_t)func == minus1) {
165      continue;
166    }
167
168    func();
169  }
170
171#ifndef LIBC_STATIC
172  {
173    extern void __libc_postfini(void) __attribute__((weak));
174    if (__libc_postfini) {
175      __libc_postfini();
176    }
177  }
178#endif
179}
180