1 /* $NetBSD: initfini.c,v 1.14 2017/06/17 15:26:44 joerg Exp $ */ 2 3 /*- 4 * Copyright (c) 2007 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Andrew Doran. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 __RCSID("$NetBSD: initfini.c,v 1.14 2017/06/17 15:26:44 joerg Exp $"); 34 35 #ifdef _LIBC 36 #include "namespace.h" 37 #endif 38 39 #include <sys/param.h> 40 #include <sys/exec.h> 41 #include <sys/tls.h> 42 #include <stdbool.h> 43 44 void _libc_init(void) __attribute__((__constructor__, __used__)); 45 46 void __guard_setup(void); 47 void __libc_thr_init(void); 48 void __libc_atomic_init(void); 49 void __libc_atexit_init(void); 50 void __libc_env_init(void); 51 52 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 53 __dso_hidden void __libc_static_tls_setup(void); 54 #endif 55 56 #ifdef __weak_alias 57 __weak_alias(_dlauxinfo,___dlauxinfo) 58 static void *__libc_dlauxinfo; 59 60 void *___dlauxinfo(void) __pure; 61 __weakref_visible void * real_dlauxinfo(void) __weak_reference(_dlauxinfo); 62 63 void * 64 ___dlauxinfo(void) 65 { 66 return __libc_dlauxinfo; 67 } 68 #endif 69 70 static bool libc_initialised; 71 72 void _libc_init(void); 73 74 /* 75 * Declare as common symbol to allow new libc with older binaries to 76 * not trigger an undefined reference. 77 */ 78 struct ps_strings *__ps_strings; 79 80 /* 81 * _libc_init is called twice. One call comes explicitly from crt0.o 82 * (for newer versions) and the other is via global constructor handling. 83 * 84 * In static binaries the explicit call is first; in dynamically linked 85 * binaries the global constructors of libc are called from ld.elf_so 86 * before crt0.o is reached. 87 * 88 * Note that __ps_strings is set by crt0.o. So in the dynamic case, it 89 * hasn't been set yet when we get here, and __libc_dlauxinfo is not 90 * (ever) assigned. But this is ok because __libc_dlauxinfo is only 91 * used in static binaries, because it's there to substitute for the 92 * dynamic linker. In static binaries __ps_strings will have been set 93 * up when we get here and we get a valid __libc_dlauxinfo. 94 * 95 * This code causes problems for Emacs because Emacs's undump 96 * mechanism saves the __ps_strings value from the startup execution; 97 * then running the resulting binary it gets here before crt0 has 98 * assigned the current execution's value to __ps_strings, and in an 99 * environment with ASLR this can cause the assignment of 100 * __libc_dlauxinfo to receive SIGSEGV. 101 */ 102 void __section(".text.startup") 103 _libc_init(void) 104 { 105 106 if (libc_initialised) 107 return; 108 109 libc_initialised = 1; 110 111 /* Only initialize _dlauxinfo for static binaries. */ 112 if (__ps_strings != NULL && real_dlauxinfo == ___dlauxinfo) 113 __libc_dlauxinfo = __ps_strings->ps_argvstr + 114 __ps_strings->ps_nargvstr + __ps_strings->ps_nenvstr + 2; 115 116 /* For -fstack-protector */ 117 __guard_setup(); 118 119 /* Atomic operations */ 120 __libc_atomic_init(); 121 122 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II) 123 /* Initialize TLS for statically linked programs. */ 124 __libc_static_tls_setup(); 125 #endif 126 127 /* Threads */ 128 __libc_thr_init(); 129 130 /* Initialize the atexit mutexes */ 131 __libc_atexit_init(); 132 133 /* Initialize environment memory RB tree. */ 134 __libc_env_init(); 135 } 136