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 * libc_init_dynamic.c
30 *
31 * This source files provides two important functions for dynamic
32 * executables:
33 *
34 * - a C runtime initializer (__libc_preinit), which is called by
35 *   the dynamic linker when libc.so is loaded. This happens before
36 *   any other initializer (e.g. static C++ constructors in other
37 *   shared libraries the program depends on).
38 *
39 * - a program launch function (__libc_init), which is called after
40 *   all dynamic linking has been performed. Technically, it is called
41 *   from arch-$ARCH/bionic/crtbegin_dynamic.S which is itself called
42 *   by the dynamic linker after all libraries have been loaded and
43 *   initialized.
44 */
45
46#include <stddef.h>
47#include <stdio.h>
48#include <stdlib.h>
49#include <stdint.h>
50#include <elf.h>
51#include "atexit.h"
52#include "libc_init_common.h"
53#include <bionic_tls.h>
54
55/* We flag the __libc_preinit function as a constructor to ensure
56 * that its address is listed in libc.so's .init_array section.
57 * This ensures that the function is called by the dynamic linker
58 * as soon as the shared library is loaded.
59 */
60void __attribute__((constructor)) __libc_preinit(void);
61
62void __libc_preinit(void)
63{
64    /* Read the ELF data pointer from a special slot of the
65     * TLS area, then call __libc_init_common with it.
66     *
67     * Note that:
68     * - we clear the slot so no other initializer sees its value.
69     * - __libc_init_common() will change the TLS area so the old one
70     *   won't be accessible anyway.
71     */
72    void**      tls_area = (void**)__get_tls();
73    unsigned*   elfdata   = tls_area[TLS_SLOT_BIONIC_PREINIT];
74
75    tls_area[TLS_SLOT_BIONIC_PREINIT] = NULL;
76
77    __libc_init_common(elfdata);
78
79    /* Setup pthread routines accordingly to the environment.
80     * Requires system properties
81     */
82    extern void pthread_debug_init(void);
83    pthread_debug_init();
84
85    /* Setup malloc routines accordingly to the environment.
86     * Requires system properties
87     */
88    extern void malloc_debug_init(void);
89    malloc_debug_init();
90}
91
92void __libc_postfini(void)
93{
94    extern void malloc_debug_fini(void);
95    malloc_debug_fini();
96}
97
98/* This function is called from the executable's _start entry point
99 * (see arch-$ARCH/bionic/crtbegin_dynamic.S), which is itself
100 * called by the dynamic linker after it has loaded all shared
101 * libraries the executable depends on.
102 *
103 * Note that the dynamic linker has also run all constructors in the
104 * executable at this point.
105 */
106__noreturn void __libc_init(uintptr_t *elfdata,
107                       void (*onexit)(void),
108                       int (*slingshot)(int, char**, char**),
109                       structors_array_t const * const structors)
110{
111    int     argc = (int)*elfdata;
112    char**  argv = (char**)(elfdata + 1);
113    char**  envp = argv + argc + 1;
114
115    /* Several Linux ABIs don't pass the onexit pointer, and the ones that
116     * do never use it.  Therefore, we ignore it.
117     */
118
119    /* The executable may have its own destructors listed in its .fini_array
120     * so we need to ensure that these are called when the program exits
121     * normally.
122     */
123    if (structors->fini_array)
124        __cxa_atexit(__libc_fini,structors->fini_array,NULL);
125
126    exit(slingshot(argc, argv, envp));
127}
128