annotate lib/c-stack.c @ 16511:2074f2bf7216

math code: Add comments. * lib/acosl.c: Add comment about related glibc source files. * lib/asinl.c: Likewise. * lib/atanl.c: Likewise. * lib/expl.c: Likewise. * lib/logl.c: Likewise. * lib/sincosl.c: Likewise. * lib/sinl.c: Likewise. * lib/tanl.c: Likewise. * lib/trigl.c: Likewise. * lib/cosl.c: Likewise. Fix comments.
author Bruno Haible <bruno@clisp.org>
date Wed, 29 Feb 2012 12:30:07 +0100
parents a712776b11ce
children e542fd46ad6f
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 /* Stack overflow handling.
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2
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3 Copyright (C) 2002, 2004, 2006, 2008-2012 Free Software Foundation, Inc.
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4
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5 This program is free software: you can redistribute it and/or modify
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6 it under the terms of the GNU General Public License as published by
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7 the Free Software Foundation; either version 3 of the License, or
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8 (at your option) any later version.
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9
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10 This program is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 GNU General Public License for more details.
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14
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15 You should have received a copy of the GNU General Public License
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16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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17
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18 /* Written by Paul Eggert. */
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19
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20 /* NOTES:
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21
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22 A program that uses alloca, dynamic arrays, or large local
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23 variables may extend the stack by more than a page at a time. If
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24 so, when the stack overflows the operating system may not detect
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25 the overflow until the program uses the array, and this module may
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26 incorrectly report a program error instead of a stack overflow.
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27
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28 To avoid this problem, allocate only small objects on the stack; a
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29 program should be OK if it limits single allocations to a page or
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30 less. Allocate larger arrays in static storage, or on the heap
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31 (e.g., with malloc). Yes, this is a pain, but we don't know of any
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32 better solution that is portable.
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33
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34 No attempt has been made to deal with multithreaded applications. */
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35
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36 #include <config.h>
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37
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38 #ifndef __attribute__
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39 # if __GNUC__ < 3
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40 # define __attribute__(x)
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41 # endif
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42 #endif
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43
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44 #include "gettext.h"
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45 #define _(msgid) gettext (msgid)
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46
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47 #include <errno.h>
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48
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49 #include <signal.h>
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50 #if ! HAVE_STACK_T && ! defined stack_t
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51 typedef struct sigaltstack stack_t;
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52 #endif
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53 #ifndef SIGSTKSZ
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54 # define SIGSTKSZ 16384
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55 #elif HAVE_LIBSIGSEGV && SIGSTKSZ < 16384
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56 /* libsigsegv 2.6 through 2.8 have a bug where some architectures use
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57 more than the Linux default of an 8k alternate stack when deciding
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58 if a fault was caused by stack overflow. */
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59 # undef SIGSTKSZ
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60 # define SIGSTKSZ 16384
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61 #endif
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62
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63 #include <stdlib.h>
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64 #include <string.h>
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65
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66 /* Posix 2001 declares ucontext_t in <ucontext.h>, Posix 200x in
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67 <signal.h>. */
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68 #if HAVE_UCONTEXT_H
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69 # include <ucontext.h>
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70 #endif
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71
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72 #include <unistd.h>
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73
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74 #if HAVE_LIBSIGSEGV
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75 # include <sigsegv.h>
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76 #endif
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77
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78 #include "c-stack.h"
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79 #include "exitfail.h"
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80 #include "ignore-value.h"
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81
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82 #if defined SA_ONSTACK && defined SA_SIGINFO
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83 # define SIGINFO_WORKS 1
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84 #else
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85 # define SIGINFO_WORKS 0
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86 # ifndef SA_ONSTACK
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87 # define SA_ONSTACK 0
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88 # endif
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89 #endif
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90
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91 extern char *program_name;
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92
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93 /* The user-specified action to take when a SEGV-related program error
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94 or stack overflow occurs. */
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95 static void (* volatile segv_action) (int);
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96
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97 /* Translated messages for program errors and stack overflow. Do not
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98 translate them in the signal handler, since gettext is not
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99 async-signal-safe. */
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100 static char const * volatile program_error_message;
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101 static char const * volatile stack_overflow_message;
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102
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103 /* Output an error message, then exit with status EXIT_FAILURE if it
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104 appears to have been a stack overflow, or with a core dump
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105 otherwise. This function is async-signal-safe. */
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106
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107 static _Noreturn void
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108 die (int signo)
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109 {
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110 char const *message;
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111 #if !SIGINFO_WORKS && !HAVE_LIBSIGSEGV
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112 /* We can't easily determine whether it is a stack overflow; so
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113 assume that the rest of our program is perfect (!) and that
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114 this segmentation violation is a stack overflow. */
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115 signo = 0;
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116 #endif /* !SIGINFO_WORKS && !HAVE_LIBSIGSEGV */
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117 segv_action (signo);
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118 message = signo ? program_error_message : stack_overflow_message;
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119 ignore_value (write (STDERR_FILENO, program_name, strlen (program_name)));
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120 ignore_value (write (STDERR_FILENO, ": ", 2));
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121 ignore_value (write (STDERR_FILENO, message, strlen (message)));
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122 ignore_value (write (STDERR_FILENO, "\n", 1));
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123 if (! signo)
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124 _exit (exit_failure);
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125 raise (signo);
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126 abort ();
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127 }
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128
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129 #if (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK \
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130 && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV
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131
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132 /* Storage for the alternate signal stack. */
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133 static union
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134 {
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135 char buffer[SIGSTKSZ];
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136
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137 /* These other members are for proper alignment. There's no
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138 standard way to guarantee stack alignment, but this seems enough
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139 in practice. */
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140 long double ld;
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141 long l;
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142 void *p;
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143 } alternate_signal_stack;
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144
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145 static void
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146 null_action (int signo __attribute__ ((unused)))
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147 {
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148 }
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149
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150 #endif /* SIGALTSTACK || LIBSIGSEGV */
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151
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152 /* Only use libsigsegv if we need it; platforms like Solaris can
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153 detect stack overflow without the overhead of an external
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154 library. */
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155 #if HAVE_LIBSIGSEGV && ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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156
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157 /* Nonzero if general segv handler could not be installed. */
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158 static volatile int segv_handler_missing;
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159
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160 /* Handle a segmentation violation and exit if it cannot be stack
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161 overflow. This function is async-signal-safe. */
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162
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163 static int segv_handler (void *address __attribute__ ((unused)),
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164 int serious)
10276
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165 {
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166 # if DEBUG
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167 {
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168 char buf[1024];
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169 sprintf (buf, "segv_handler serious=%d\n", serious);
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170 write (STDERR_FILENO, buf, strlen (buf));
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171 }
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172 # endif
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173
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174 /* If this fault is not serious, return 0 to let the stack overflow
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175 handler take a shot at it. */
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176 if (!serious)
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177 return 0;
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178 die (SIGSEGV);
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179 }
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180
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181 /* Handle a segmentation violation that is likely to be a stack
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diff changeset
182 overflow and exit. This function is async-signal-safe. */
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183
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184 static _Noreturn void
10276
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185 overflow_handler (int emergency,
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186 stackoverflow_context_t context __attribute__ ((unused)))
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187 {
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188 # if DEBUG
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189 {
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190 char buf[1024];
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191 sprintf (buf, "overflow_handler emergency=%d segv_handler_missing=%d\n",
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192 emergency, segv_handler_missing);
10276
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193 write (STDERR_FILENO, buf, strlen (buf));
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194 }
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195 # endif
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196
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197 die ((!emergency || segv_handler_missing) ? 0 : SIGSEGV);
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198 }
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199
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200 int
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201 c_stack_action (void (*action) (int))
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202 {
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203 segv_action = action ? action : null_action;
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204 program_error_message = _("program error");
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205 stack_overflow_message = _("stack overflow");
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206
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207 /* Always install the overflow handler. */
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208 if (stackoverflow_install_handler (overflow_handler,
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209 alternate_signal_stack.buffer,
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210 sizeof alternate_signal_stack.buffer))
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211 {
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212 errno = ENOTSUP;
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213 return -1;
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214 }
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215 /* Try installing a general handler; if it fails, then treat all
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diff changeset
216 segv as stack overflow. */
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217 segv_handler_missing = sigsegv_install_handler (segv_handler);
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218 return 0;
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219 }
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220
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221 #elif HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK && HAVE_STACK_OVERFLOW_HANDLING
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222
14184
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223 # if SIGINFO_WORKS
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224
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225 /* Handle a segmentation violation and exit. This function is
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226 async-signal-safe. */
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227
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228 static _Noreturn void
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229 segv_handler (int signo, siginfo_t *info,
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230 void *context __attribute__ ((unused)))
3902
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diff changeset
231 {
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232 /* Clear SIGNO if it seems to have been a stack overflow. */
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233 # if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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234 /* We can't easily determine whether it is a stack overflow; so
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diff changeset
235 assume that the rest of our program is perfect (!) and that
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diff changeset
236 this segmentation violation is a stack overflow.
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237
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238 Note that although both Linux and Solaris provide
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diff changeset
239 sigaltstack, SA_ONSTACK, and SA_SIGINFO, currently only
16358
a712776b11ce maint: spelling fixes
Paul Eggert <eggert@cs.ucla.edu>
parents: 16201
diff changeset
240 Solaris satisfies the XSI heuristic. This is because
11077
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diff changeset
241 Solaris populates uc_stack with the details of the
ddb65537c2d0 On HP-UX, don't pretend it was a SIGSEGV when it was a stack overflow.
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diff changeset
242 interrupted stack, while Linux populates it with the details
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diff changeset
243 of the current stack. */
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244 signo = 0;
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diff changeset
245 # else
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diff changeset
246 if (0 < info->si_code)
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diff changeset
247 {
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diff changeset
248 /* If the faulting address is within the stack, or within one
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Paul Eggert <eggert@cs.ucla.edu>
parents: 14225
diff changeset
249 page of the stack, assume that it is a stack overflow. */
3902
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250 ucontext_t const *user_context = context;
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diff changeset
251 char const *stack_base = user_context->uc_stack.ss_sp;
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parents:
diff changeset
252 size_t stack_size = user_context->uc_stack.ss_size;
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parents:
diff changeset
253 char const *faulting_address = info->si_addr;
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diff changeset
254 size_t page_size = sysconf (_SC_PAGESIZE);
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parents: 14225
diff changeset
255 size_t s = faulting_address - stack_base + page_size;
5fa23c9b72d6 c-stack: stop worrying about stack direction
Paul Eggert <eggert@cs.ucla.edu>
parents: 14225
diff changeset
256 if (s < stack_size + 2 * page_size)
12421
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diff changeset
257 signo = 0;
3902
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diff changeset
258
4915
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parents: 3921
diff changeset
259 # if DEBUG
3902
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diff changeset
260 {
12421
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diff changeset
261 char buf[1024];
e8d2c6fc33ad Use spaces for indentation, not tabs.
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diff changeset
262 sprintf (buf,
e8d2c6fc33ad Use spaces for indentation, not tabs.
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diff changeset
263 "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
e8d2c6fc33ad Use spaces for indentation, not tabs.
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parents: 12335
diff changeset
264 faulting_address, stack_base, (unsigned long) stack_size,
e8d2c6fc33ad Use spaces for indentation, not tabs.
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diff changeset
265 (unsigned long) page_size, signo);
e8d2c6fc33ad Use spaces for indentation, not tabs.
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diff changeset
266 write (STDERR_FILENO, buf, strlen (buf));
3902
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diff changeset
267 }
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diff changeset
268 # endif
11077
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269 }
3902
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270 # endif
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271
f26afed46772 New file, from diffutils-2.8.2.
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diff changeset
272 die (signo);
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273 }
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diff changeset
274 # endif
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275
f26afed46772 New file, from diffutils-2.8.2.
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parents:
diff changeset
276 int
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277 c_stack_action (void (*action) (int))
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278 {
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279 int r;
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280 stack_t st;
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281 struct sigaction act;
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282 st.ss_flags = 0;
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283 # if SIGALTSTACK_SS_REVERSED
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284 /* Irix mistakenly treats ss_sp as the upper bound, rather than
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285 lower bound, of the alternate stack. */
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286 st.ss_sp = alternate_signal_stack.buffer + SIGSTKSZ - sizeof (void *);
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287 st.ss_size = sizeof alternate_signal_stack.buffer - sizeof (void *);
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288 # else
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289 st.ss_sp = alternate_signal_stack.buffer;
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290 st.ss_size = sizeof alternate_signal_stack.buffer;
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291 # endif
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292 r = sigaltstack (&st, NULL);
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293 if (r != 0)
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294 return r;
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295
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296 segv_action = action ? action : null_action;
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297 program_error_message = _("program error");
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298 stack_overflow_message = _("stack overflow");
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299
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300 sigemptyset (&act.sa_mask);
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301
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302 # if SIGINFO_WORKS
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303 /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
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304 this is not true on Solaris 8 at least. It doesn't hurt to use
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305 SA_NODEFER here, so leave it in. */
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306 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
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307 act.sa_sigaction = segv_handler;
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308 # else
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309 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND;
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310 act.sa_handler = die;
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311 # endif
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312
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313 # if FAULT_YIELDS_SIGBUS
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314 if (sigaction (SIGBUS, &act, NULL) < 0)
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315 return -1;
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316 # endif
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317 return sigaction (SIGSEGV, &act, NULL);
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318 }
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319
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320 #else /* ! ((HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
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321 && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV) */
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322
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323 int
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324 c_stack_action (void (*action) (int) __attribute__ ((unused)))
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325 {
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326 errno = ENOTSUP;
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327 return -1;
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328 }
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329
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330 #endif