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annotate lib/c-stack.c @ 10470:9867f4fee019

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c-stack: work around Irix sigaltstack bug * m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Check whether sigaltstack uses wrong end of stack_t (copied in part from libsigsegv). * lib/c-stack.c (c_stack_action) [!HAVE_LIBSIGSEGV]: Work around Irix bug, without requiring an over-allocation. * doc/posix-functions/sigaltstack.texi (sigaltstack): Document the bug. Signed-off-by: Eric Blake <ebb9@byu.net>
author Eric Blake <ebb9@byu.net>
date Tue, 23 Sep 2008 08:47:26 -0600
parents 37fd490ee38d
children d31da80e6c50
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1 /* Stack overflow handling.
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2
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3 Copyright (C) 2002, 2004, 2006, 2008 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 #ifndef ENOTSUP
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49 # define ENOTSUP EINVAL
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50 #endif
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51
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52 #include <signal.h>
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53 #if ! HAVE_STACK_T && ! defined stack_t
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54 typedef struct sigaltstack stack_t;
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55 #endif
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56 #ifndef SIGSTKSZ
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57 # define SIGSTKSZ 16384
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58 #endif
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59
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60 #include <stdlib.h>
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61 #include <string.h>
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62
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63 /* Posix 2001 declares ucontext_t in <ucontext.h>, Posix 200x in
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64 <signal.h>. */
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65 #if HAVE_UCONTEXT_H
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66 # include <ucontext.h>
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67 #endif
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68
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69 #include <unistd.h>
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70 #ifndef STDERR_FILENO
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71 # define STDERR_FILENO 2
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72 #endif
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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
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81 #if defined SA_ONSTACK && defined SA_SIGINFO
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82 # define SIGACTION_WORKS 1
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83 #else
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84 # define SIGACTION_WORKS 0
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85 #endif
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86
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87 extern char *program_name;
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88
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89 /* The user-specified action to take when a SEGV-related program error
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90 or stack overflow occurs. */
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91 static void (* volatile segv_action) (int);
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92
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93 /* Translated messages for program errors and stack overflow. Do not
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94 translate them in the signal handler, since gettext is not
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95 async-signal-safe. */
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96 static char const * volatile program_error_message;
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97 static char const * volatile stack_overflow_message;
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98
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99 /* Output an error message, then exit with status EXIT_FAILURE if it
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100 appears to have been a stack overflow, or with a core dump
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101 otherwise. This function is async-signal-safe. */
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102
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103 static void die (int) __attribute__ ((noreturn));
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104 static void
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105 die (int signo)
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106 {
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107 char const *message;
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108 segv_action (signo);
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109 message = signo ? program_error_message : stack_overflow_message;
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110 write (STDERR_FILENO, program_name, strlen (program_name));
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111 write (STDERR_FILENO, ": ", 2);
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112 write (STDERR_FILENO, message, strlen (message));
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113 write (STDERR_FILENO, "\n", 1);
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114 if (! signo)
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115 _exit (exit_failure);
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116 raise (signo);
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117 abort ();
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118 }
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119
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120 #if (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK \
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121 && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV
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122
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123 /* Storage for the alternate signal stack. */
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124 static union
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125 {
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126 char buffer[SIGSTKSZ];
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127
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128 /* These other members are for proper alignment. There's no
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129 standard way to guarantee stack alignment, but this seems enough
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130 in practice. */
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131 long double ld;
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132 long l;
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133 void *p;
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134 } alternate_signal_stack;
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135
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136 static void
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137 null_action (int signo __attribute__ ((unused)))
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138 {
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139 }
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140
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141 #endif /* SIGALTSTACK || LIBSIGSEGV */
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142
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143 /* Only use libsigsegv if we need it; platforms like Solaris can
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144 detect stack overflow without the overhead of an external
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145 library. */
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146 #if HAVE_LIBSIGSEGV && ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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147
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148 /* Nonzero if general segv handler could not be installed. */
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149 static volatile int segv_handler_missing;
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150
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151 /* Handle a segmentation violation and exit if it cannot be stack
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152 overflow. This function is async-signal-safe. */
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153
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154 static int segv_handler (void *address __attribute__ ((unused)),
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155 int serious)
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156 {
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157 # if DEBUG
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158 {
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159 char buf[1024];
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160 sprintf (buf, "segv_handler serious=%d\n", serious);
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161 write (STDERR_FILENO, buf, strlen (buf));
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162 }
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163 # endif
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164
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165 /* If this fault is not serious, return 0 to let the stack overflow
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166 handler take a shot at it. */
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167 if (!serious)
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168 return 0;
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169 die (SIGSEGV);
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170 }
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171
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172 /* Handle a segmentation violation that is likely to be a stack
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173 overflow and exit. This function is async-signal-safe. */
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174
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175 static void overflow_handler (int, stackoverflow_context_t)
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176 __attribute__ ((noreturn));
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177 static void
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178 overflow_handler (int emergency,
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179 stackoverflow_context_t context __attribute__ ((unused)))
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180 {
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181 # if DEBUG
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182 {
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183 char buf[1024];
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184 sprintf (buf, "overflow_handler emergency=%d segv_handler_missing=%d\n",
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185 emergency, segv_handler_missing);
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186 write (STDERR_FILENO, buf, strlen (buf));
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187 }
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188 # endif
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189
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190 die ((!emergency || segv_handler_missing) ? 0 : SIGSEGV);
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191 }
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192
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193 int
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194 c_stack_action (void (*action) (int))
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195 {
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196 segv_action = action ? action : null_action;
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197 program_error_message = _("program error");
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198 stack_overflow_message = _("stack overflow");
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199
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200 /* Always install the overflow handler. */
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201 if (stackoverflow_install_handler (overflow_handler,
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202 alternate_signal_stack.buffer,
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Eric Blake <ebb9@byu.net>
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203 sizeof alternate_signal_stack.buffer))
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204 {
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205 errno = ENOTSUP;
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206 return -1;
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207 }
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208 /* Try installing a general handler; if it fails, then treat all
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209 segv as stack overflow. */
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210 segv_handler_missing = sigsegv_install_handler (segv_handler);
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211 return 0;
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212 }
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213
10358
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214 #elif HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK && HAVE_STACK_OVERFLOW_HANDLING
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215
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216 /* Direction of the C runtime stack. This function is
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217 async-signal-safe. */
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218
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219 # if STACK_DIRECTION
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220 # define find_stack_direction(ptr) STACK_DIRECTION
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221 # else
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222 static int
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223 find_stack_direction (char const *addr)
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224 {
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225 char dummy;
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226 return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
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227 }
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228 # endif
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229
4969
0db24850c598 Fix c-stack.c portability bug on IRIX 5.3.
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diff changeset
230 # if SIGACTION_WORKS
3902
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231
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232 /* Handle a segmentation violation and exit. This function is
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diff changeset
233 async-signal-safe. */
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234
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diff changeset
235 static void segv_handler (int, siginfo_t *, void *) __attribute__((noreturn));
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diff changeset
236 static void
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diff changeset
237 segv_handler (int signo, siginfo_t *info,
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diff changeset
238 void *context __attribute__ ((unused)))
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diff changeset
239 {
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diff changeset
240 /* Clear SIGNO if it seems to have been a stack overflow. */
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Jim Meyering <jim@meyering.net>
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diff changeset
241 if (0 < info->si_code)
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diff changeset
242 {
4915
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parents: 3921
diff changeset
243 # if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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244 /* We can't easily determine whether it is a stack overflow; so
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diff changeset
245 assume that the rest of our program is perfect (!) and that
10276
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diff changeset
246 this segmentation violation is a stack overflow.
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247
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diff changeset
248 Note that although both Linux and Solaris provide
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diff changeset
249 sigaltstack, SA_ONSTACK, and SA_SIGINFO, currently only
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diff changeset
250 Solaris satisfies the XSI heueristic. This is because
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diff changeset
251 Solaris populates uc_stack with the details of the
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diff changeset
252 interrupted stack, while Linux populates it with the details
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diff changeset
253 of the current stack. */
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254 signo = 0;
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diff changeset
255 # else
3902
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diff changeset
256 /* If the faulting address is within the stack, or within one
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diff changeset
257 page of the stack end, assume that it is a stack
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diff changeset
258 overflow. */
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diff changeset
259 ucontext_t const *user_context = context;
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diff changeset
260 char const *stack_base = user_context->uc_stack.ss_sp;
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diff changeset
261 size_t stack_size = user_context->uc_stack.ss_size;
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diff changeset
262 char const *faulting_address = info->si_addr;
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diff changeset
263 size_t s = faulting_address - stack_base;
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parents:
diff changeset
264 size_t page_size = sysconf (_SC_PAGESIZE);
10230
54813304edd2 Use sigaction module rather than signal().
Eric Blake <ebb9@byu.net>
parents: 10214
diff changeset
265 if (find_stack_direction (NULL) < 0)
3902
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diff changeset
266 s += page_size;
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parents:
diff changeset
267 if (s < stack_size + page_size)
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diff changeset
268 signo = 0;
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diff changeset
269
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diff changeset
270 # if DEBUG
3902
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diff changeset
271 {
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diff changeset
272 char buf[1024];
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diff changeset
273 sprintf (buf,
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diff changeset
274 "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
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parents:
diff changeset
275 faulting_address, stack_base, (unsigned long) stack_size,
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parents:
diff changeset
276 (unsigned long) page_size, signo);
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diff changeset
277 write (STDERR_FILENO, buf, strlen (buf));
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parents:
diff changeset
278 }
4915
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diff changeset
279 # endif
3902
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diff changeset
280 # endif
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diff changeset
281 }
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282
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parents:
diff changeset
283 die (signo);
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284 }
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285 # endif
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286
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287 int
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288 c_stack_action (void (*action) (int))
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289 {
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290 int r;
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291 stack_t st;
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292 struct sigaction act;
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293 st.ss_flags = 0;
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294 # if SIGALTSTACK_SS_REVERSED
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295 /* Irix mistakenly treats ss_sp as the upper bound, rather than
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296 lower bound, of the alternate stack. */
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297 st.ss_sp = alternate_signal_stack.buffer + SIGSTKSZ - sizeof (void *);
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298 st.ss_size = sizeof alternate_signal_stack.buffer - sizeof (void *);
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299 # else
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300 st.ss_sp = alternate_signal_stack.buffer;
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301 st.ss_size = sizeof alternate_signal_stack.buffer;
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302 # endif
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303 r = sigaltstack (&st, NULL);
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304 if (r != 0)
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305 return r;
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306
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307 segv_action = action ? action : null_action;
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308 program_error_message = _("program error");
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309 stack_overflow_message = _("stack overflow");
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310
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311 sigemptyset (&act.sa_mask);
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312
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313 # if SIGACTION_WORKS
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314 /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
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315 this is not true on Solaris 8 at least. It doesn't hurt to use
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316 SA_NODEFER here, so leave it in. */
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317 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
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318 act.sa_sigaction = segv_handler;
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319 # else
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320 act.sa_flags = SA_NODEFER | SA_RESETHAND;
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321 act.sa_handler = die;
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322 # endif
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323
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324 return sigaction (SIGSEGV, &act, NULL);
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325 }
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326
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327 #else /* ! ((HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
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328 && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV) */
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329
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330 int
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331 c_stack_action (void (*action) (int) __attribute__ ((unused)))
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332 {
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333 errno = ENOTSUP;
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334 return -1;
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335 }
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336
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337 #endif