contrib/diffutils-2.8.1/lib/c-stack.c

   1 /* Stack overflow handling.
   2
   3    Copyright (C) 2002 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 /* Written by Paul Eggert.  */
  20
  21 /* This module assumes that each stack frame is smaller than a page.
  22    If you use alloca, dynamic arrays, or large local variables, your
  23    program may extend the stack by more than a page at a time.  If so,
  24    the code below may incorrectly report a program error, or worse
  25    yet, may not detect the overflow at all.  To avoid this problem,
  26    don't use large local arrays.  */
  27
  28 #if HAVE_CONFIG_H
  29 # include <config.h>
  30 #endif
  31
  32 #include "gettext.h"
  33 #define _(msgid) gettext (msgid)
  34
  35 #include <errno.h>
  36 #ifndef ENOTSUP
  37 # define ENOTSUP EINVAL
  38 #endif
  39
  40 #if HAVE_INTTYPES_H
  41 # include <inttypes.h>
  42 #else
  43 # if HAVE_STDINT_H
  44 #  include <stdint.h>
  45 # endif
  46 #endif
  47
  48 #include <signal.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51
  52 #if HAVE_UNISTD_H
  53 # include <unistd.h>
  54 #endif
  55 #ifndef STDERR_FILENO
  56 # define STDERR_FILENO 2
  57 #endif
  58
  59 #include "c-stack.h"
  60 #include "exitfail.h"
  61
  62 extern char *program_name;
  63
  64 #if HAVE_XSI_STACK_OVERFLOW_HEURISTIC
  65
  66 # include <ucontext.h>
  67
  68
  69 /* Storage for the alternate signal stack.  */
  70 static union
  71 {
  72   char buffer[SIGSTKSZ];
  73
  74   /* These other members are for proper alignment.  There's no
  75      standard way to guarantee stack alignment, but this seems enough
  76      in practice.  */
  77   long double ld;
  78   uintmax_t u;
  79   void *p;
  80 } alternate_signal_stack;
  81
  82
  83 /* Direction of the C runtime stack.  This function is
  84    async-signal-safe.  */
  85
  86 # if STACK_DIRECTION
  87 #  define find_stack_direction(ptr) STACK_DIRECTION
  88 # else
  89 static int
  90 find_stack_direction (char const *addr)
  91 {
  92   char dummy;
  93   return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
  94 }
  95 # endif
  96
  97 /* The SIGSEGV handler.  */
  98 static void (* volatile segv_action) (int, siginfo_t *, void *);
  99
 100 /* Handle a segmentation violation and exit.  This function is
 101    async-signal-safe.  */
 102
 103 static void
 104 segv_handler (int signo, siginfo_t *info, void *context)
 105 {
 106   /* Clear SIGNO if it seems to have been a stack overflow.  */
 107   if (0 < info->si_code)
 108     {
 109       /* If the faulting address is within the stack, or within one
 110          page of the stack end, assume that it is a stack
 111          overflow.  */
 112       ucontext_t const *user_context = context;
 113       char const *stack_min = user_context->uc_stack.ss_sp;
 114       size_t stack_size = user_context->uc_stack.ss_size;
 115       char const *faulting_address = info->si_addr;
 116       size_t s = faulting_address - stack_min;
 117       size_t page_size = sysconf (_SC_PAGESIZE);
 118       if (find_stack_direction (0) < 0)
 119         s += page_size;
 120       if (s < stack_size + page_size)
 121         signo = 0;
 122     }
 123
 124   segv_action (signo, info, context);
 125 }
 126
 127 #endif /* HAVE_XSI_STACK_OVERFLOW_HEURISTIC */
 128
 129
 130 /* Translated messages for program errors and stack overflow.  Do not
 131    translate them in the signal handler, since gettext is not
 132    async-signal-safe.  */
 133 static char const * volatile program_error_message;
 134 static char const * volatile stack_overflow_message;
 135
 136 /* Output an error message, then exit with status EXIT_FAILURE if it
 137    appears to have been a stack overflow, or with a core dump
 138    otherwise.  This function is async-signal-safe.  */
 139
 140 void
 141 c_stack_die (int signo, siginfo_t *info, void *context)
 142 {
 143   char const *message =
 144     signo ? program_error_message : stack_overflow_message;
 145   write (STDERR_FILENO, program_name, strlen (program_name));
 146   write (STDERR_FILENO, ": ", 2);
 147   write (STDERR_FILENO, message, strlen (message));
 148   write (STDERR_FILENO, "\n", 1);
 149   if (! signo)
 150     _exit (exit_failure);
 151 #if HAVE_SIGINFO_T
 152   if (context && info && 0 <= info->si_code)
 153     {
 154       /* Re-raise the exception at the same address.  */
 155       char *addr = info->si_addr;
 156       *addr = 0;
 157     }
 158 #endif
 159   kill (getpid (), signo);
 160 }
 161
 162
 163 /* Set up ACTION so that it is invoked on C stack overflow.  Return -1
 164    (setting errno) if this cannot be done.
 165
 166    ACTION must invoke only async-signal-safe functions.  ACTION
 167    together with its callees must not require more than SIGSTKSZ bytes
 168    of stack space.  */
 169
 170 int
 171 c_stack_action (void (*action) (int, siginfo_t *, void *))
 172 {
 173 #if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
 174   errno = ENOTSUP;
 175   return -1;
 176 #else
 177   struct sigaction act;
 178   stack_t st;
 179   int r;
 180
 181   st.ss_flags = 0;
 182   st.ss_sp = alternate_signal_stack.buffer;
 183   st.ss_size = sizeof alternate_signal_stack.buffer;
 184   r = sigaltstack (&st, 0);
 185   if (r != 0)
 186     return r;
 187
 188   program_error_message = _("program error");
 189   stack_overflow_message = _("stack overflow");
 190   segv_action = action;
 191
 192   sigemptyset (&act.sa_mask);
 193
 194   /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but this
 195      is not true on Solaris 8 at least.  It doesn't hurt to use
 196      SA_NODEFER here, so leave it in.  */
 197   act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
 198
 199   act.sa_sigaction = segv_handler;
 200   return sigaction (SIGSEGV, &act, 0);
 201 #endif
 202 }
 203 \f
 204 #if DEBUG
 205
 206 #include <stdio.h>
 207
 208 int volatile exit_failure;
 209
 210 static long
 211 recurse (char *p)
 212 {
 213   char array[500];
 214   array[0] = 1;
 215   return *p + recurse (array);
 216 }
 217
 218 char *program_name;
 219
 220 int
 221 main (int argc, char **argv)
 222 {
 223   program_name = argv[0];
 224   c_stack_action (c_stack_die);
 225   return recurse ("\1");
 226 }
 227
 228 #endif /* DEBUG */
 229 \f
 230 /*
 231 Local Variables:
 232 compile-command: "gcc -D_GNU_SOURCE -DDEBUG \
 233   -DHAVE_INTTYPES_H -DHAVE_SIGINFO_T \
 234   -DHAVE_XSI_STACK_OVERFLOW_HEURISTIC -DHAVE_UNISTD_H \
 235   -Wall -W -g c-stack.c -o c-stack"
 236 End:
 237 */