initfini.c revision 1.16 
1/* 	$NetBSD: initfini.c,v 1.16 2023/07/18 11:44:32 riastradh 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 1.16 2023/07/18 11:44:32 riastradh 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 "csu-common.h"
44
45void	_libc_init(void) __attribute__((__constructor__, __used__));
46
47void	__guard_setup(void);
48void	__libc_thr_init(void);
49void	__libc_atomic_init(void);
50void	__libc_atexit_init(void);
51void	__libc_env_init(void);
52
53#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
54__dso_hidden void	__libc_static_tls_setup(void);
55#endif
56
57#ifdef __weak_alias
58__weak_alias(_dlauxinfo,___dlauxinfo)
59static void *__libc_dlauxinfo;
60
61void *___dlauxinfo(void) __pure;
62__weakref_visible void * real_dlauxinfo(void) __weak_reference(_dlauxinfo);
63
64void *
65___dlauxinfo(void)
66{
67	return __libc_dlauxinfo;
68}
69#endif
70
71static bool libc_initialised;
72
73void _libc_init(void);
74
75/*
76 * Declare as common symbol to allow new libc with older binaries to
77 * not trigger an undefined reference.
78 */
79struct ps_strings *__ps_strings __common;
80char *__progname __common;
81char **environ __common;
82
83/*
84 * _libc_init is called twice.  One call comes explicitly from crt0.o
85 * (for newer versions) and the other is via global constructor handling.
86 *
87 * In static binaries the explicit call is first; in dynamically linked
88 * binaries the global constructors of libc are called from ld.elf_so
89 * before crt0.o is reached.
90 *
91 * Note that __ps_strings is set by crt0.o. So in the dynamic case, it
92 * hasn't been set yet when we get here, and __libc_dlauxinfo is not
93 * (ever) assigned. But this is ok because __libc_dlauxinfo is only
94 * used in static binaries, because it's there to substitute for the
95 * dynamic linker. In static binaries __ps_strings will have been set
96 * up when we get here and we get a valid __libc_dlauxinfo.
97 *
98 * This code causes problems for Emacs because Emacs's undump
99 * mechanism saves the __ps_strings value from the startup execution;
100 * then running the resulting binary it gets here before crt0 has
101 * assigned the current execution's value to __ps_strings, and in an
102 * environment with ASLR this can cause the assignment of
103 * __libc_dlauxinfo to receive SIGSEGV.
104 */
105void __section(".text.startup")
106_libc_init(void)
107{
108
109	if (libc_initialised)
110		return;
111
112	libc_initialised = 1;
113
114	/* Only initialize _dlauxinfo for static binaries. */
115	if (__ps_strings != NULL && real_dlauxinfo == ___dlauxinfo)
116		__libc_dlauxinfo = __ps_strings->ps_argvstr +
117		    __ps_strings->ps_nargvstr + __ps_strings->ps_nenvstr + 2;
118
119	/* For -fstack-protector */
120	__guard_setup();
121
122	/* Atomic operations */
123	__libc_atomic_init();
124
125#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
126	/* Initialize TLS for statically linked programs. */
127	__libc_static_tls_setup();
128#endif
129
130	/* Threads */
131	__libc_thr_init();
132
133	/* Initialize the atexit mutexes */
134	__libc_atexit_init();
135}
136