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      1 /* 	$NetBSD: initfini.c,v 1.17 2024/01/20 14:52:48 christos 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 1.17 2024/01/20 14:52:48 christos 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 #include "extern.h"
     44 #include "csu-common.h"
     45 
     46 void	__guard_setup(void);
     47 void	__libc_thr_init(void);
     48 void	__libc_atexit_init(void);
     49 void	__libc_env_init(void);
     50 
     51 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
     52 __dso_hidden void	__libc_static_tls_setup(void);
     53 #endif
     54 
     55 #ifdef __weak_alias
     56 __weak_alias(_dlauxinfo,___dlauxinfo)
     57 static void *__libc_dlauxinfo;
     58 
     59 void *___dlauxinfo(void) __pure;
     60 __weakref_visible void * real_dlauxinfo(void) __weak_reference(_dlauxinfo);
     61 
     62 void *
     63 ___dlauxinfo(void)
     64 {
     65 	return __libc_dlauxinfo;
     66 }
     67 #endif
     68 
     69 static bool libc_initialised;
     70 
     71 /*
     72  * Declare as common symbol to allow new libc with older binaries to
     73  * not trigger an undefined reference.
     74  */
     75 struct ps_strings *__ps_strings __common;
     76 char *__progname __common;
     77 char **environ __common;
     78 
     79 /*
     80  * _libc_init is called twice.  One call comes explicitly from crt0.o
     81  * (for newer versions) and the other is via global constructor handling.
     82  *
     83  * In static binaries the explicit call is first; in dynamically linked
     84  * binaries the global constructors of libc are called from ld.elf_so
     85  * before crt0.o is reached.
     86  *
     87  * Note that __ps_strings is set by crt0.o. So in the dynamic case, it
     88  * hasn't been set yet when we get here, and __libc_dlauxinfo is not
     89  * (ever) assigned. But this is ok because __libc_dlauxinfo is only
     90  * used in static binaries, because it's there to substitute for the
     91  * dynamic linker. In static binaries __ps_strings will have been set
     92  * up when we get here and we get a valid __libc_dlauxinfo.
     93  *
     94  * This code causes problems for Emacs because Emacs's undump
     95  * mechanism saves the __ps_strings value from the startup execution;
     96  * then running the resulting binary it gets here before crt0 has
     97  * assigned the current execution's value to __ps_strings, and in an
     98  * environment with ASLR this can cause the assignment of
     99  * __libc_dlauxinfo to receive SIGSEGV.
    100  */
    101 void __section(".text.startup")
    102 _libc_init(void)
    103 {
    104 
    105 	if (libc_initialised)
    106 		return;
    107 
    108 	libc_initialised = 1;
    109 
    110 	/* Only initialize _dlauxinfo for static binaries. */
    111 	if (__ps_strings != NULL && real_dlauxinfo == ___dlauxinfo)
    112 		__libc_dlauxinfo = __ps_strings->ps_argvstr +
    113 		    __ps_strings->ps_nargvstr + __ps_strings->ps_nenvstr + 2;
    114 
    115 	/* For -fstack-protector */
    116 	__guard_setup();
    117 
    118 	/* Atomic operations */
    119 	__libc_atomic_init();
    120 
    121 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
    122 	/* Initialize TLS for statically linked programs. */
    123 	__libc_static_tls_setup();
    124 #endif
    125 
    126 	/* Threads */
    127 	__libc_thr_init();
    128 
    129 	/* Initialize the atexit mutexes */
    130 	__libc_atexit_init();
    131 }
    132