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