libc_init_common.cpp revision cef3faec0ea40fdfe58e425fd0be64f00de6a26d 
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 "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"
48
49extern "C" abort_msg_t** __abort_message_ptr;
50extern "C" uintptr_t __get_sp(void);
51extern "C" int __system_properties_init(void);
52extern "C" int __set_tls(void* ptr);
53extern "C" int __set_tid_address(int* tid_address);
54
55// Not public, but well-known in the BSDs.
56const char* __progname;
57
58// Declared in <unistd.h>.
59char** environ;
60
61// Declared in "private/bionic_ssp.h".
62uintptr_t __stack_chk_guard = 0;
63
64static 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}
74
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 */
86void __libc_init_tls(KernelArgumentBlock& args) {
87  __libc_auxv = args.auxv;
88
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;
92
93  static void* tls[BIONIC_TLS_SLOTS];
94  static pthread_internal_t main_thread;
95  main_thread.tls = tls;
96
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);
99
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;
105
106  __init_thread(&main_thread, false);
107  __init_tls(&main_thread);
108  __set_tls(main_thread.tls);
109  tls[TLS_SLOT_BIONIC_PREINIT] = &args;
110
111  __init_alternate_signal_stack(&main_thread);
112}
113
114void __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;
121
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));
124
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);
128
129  __system_properties_init(); // Requires 'environ'.
130}
131
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 */
139void __libc_fini(void* array) {
140  void** fini_array = reinterpret_cast<void**>(array);
141  const size_t minus1 = ~(size_t)0; /* ensure proper sign extension */
142
143  /* Sanity check - first entry must be -1 */
144  if (array == NULL || (size_t)fini_array[0] != minus1) {
145    return;
146  }
147
148  /* skip over it */
149  fini_array += 1;
150
151  /* Count the number of destructors. */
152  int count = 0;
153  while (fini_array[count] != NULL) {
154    ++count;
155  }
156
157  /* Now call each destructor in reverse order. */
158  while (count > 0) {
159    void (*func)() = (void (*)()) fini_array[--count];
160
161    /* Sanity check, any -1 in the list is ignored */
162    if ((size_t)func == minus1) {
163      continue;
164    }
165
166    func();
167  }
168
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}
178