gnu/dist/diffutils/lib/c-stack.c

   1 /*      $NetBSD$        */
   2
   3 /* Stack overflow handling.
   4
   5    Copyright (C) 2002 Free Software Foundation, Inc.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2, or (at your option)
  10    any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software Foundation,
  19    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  20
  21 /* Written by Paul Eggert.  */
  22
  23 /* This module assumes that each stack frame is smaller than a page.
  24    If you use alloca, dynamic arrays, or large local variables, your
  25    program may extend the stack by more than a page at a time.  If so,
  26    the code below may incorrectly report a program error, or worse
  27    yet, may not detect the overflow at all.  To avoid this problem,
  28    don't use large local arrays.  */
  29
  30 #if HAVE_CONFIG_H
  31 # include <config.h>
  32 #endif
  33
  34 #include "gettext.h"
  35 #define _(msgid) gettext (msgid)
  36
  37 #include <errno.h>
  38 #ifndef ENOTSUP
  39 # define ENOTSUP EINVAL
  40 #endif
  41
  42 #if HAVE_INTTYPES_H
  43 # include <inttypes.h>
  44 #else
  45 # if HAVE_STDINT_H
  46 #  include <stdint.h>
  47 # endif
  48 #endif
  49
  50 #include <signal.h>
  51 #include <stdlib.h>
  52 #include <string.h>
  53
  54 #if HAVE_UNISTD_H
  55 # include <unistd.h>
  56 #endif
  57 #ifndef STDERR_FILENO
  58 # define STDERR_FILENO 2
  59 #endif
  60
  61 #include "c-stack.h"
  62 #include "exitfail.h"
  63
  64 extern char *program_name;
  65
  66 #if HAVE_XSI_STACK_OVERFLOW_HEURISTIC
  67
  68 # include <ucontext.h>
  69
  70
  71 /* Storage for the alternate signal stack.  */
  72 static union
  73 {
  74   char buffer[SIGSTKSZ];
  75
  76   /* These other members are for proper alignment.  There's no
  77      standard way to guarantee stack alignment, but this seems enough
  78      in practice.  */
  79   long double ld;
  80   uintmax_t u;
  81   void *p;
  82 } alternate_signal_stack;
  83
  84
  85 /* Direction of the C runtime stack.  This function is
  86    async-signal-safe.  */
  87
  88 # if STACK_DIRECTION
  89 #  define find_stack_direction(ptr) STACK_DIRECTION
  90 # else
  91 static int
  92 find_stack_direction (char const *addr)
  93 {
  94   char dummy;
  95   return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
  96 }
  97 # endif
  98
  99 /* The SIGSEGV handler.  */
 100 static void (* volatile segv_action) (int, siginfo_t *, void *);
 101
 102 /* Handle a segmentation violation and exit.  This function is
 103    async-signal-safe.  */
 104
 105 static void
 106 segv_handler (int signo, siginfo_t *info, void *context)
 107 {
 108   /* Clear SIGNO if it seems to have been a stack overflow.  */
 109   if (0 < info->si_code)
 110     {
 111       /* If the faulting address is within the stack, or within one
 112          page of the stack end, assume that it is a stack
 113          overflow.  */
 114       ucontext_t const *user_context = context;
 115       char const *stack_min = user_context->uc_stack.ss_sp;
 116       size_t stack_size = user_context->uc_stack.ss_size;
 117       char const *faulting_address = info->si_addr;
 118       size_t s = faulting_address - stack_min;
 119       size_t page_size = sysconf (_SC_PAGESIZE);
 120       if (find_stack_direction (0) < 0)
 121         s += page_size;
 122       if (s < stack_size + page_size)
 123         signo = 0;
 124     }
 125
 126   segv_action (signo, info, context);
 127 }
 128
 129 #endif /* HAVE_XSI_STACK_OVERFLOW_HEURISTIC */
 130
 131
 132 /* Translated messages for program errors and stack overflow.  Do not
 133    translate them in the signal handler, since gettext is not
 134    async-signal-safe.  */
 135 static char const * volatile program_error_message;
 136 static char const * volatile stack_overflow_message;
 137
 138 /* Output an error message, then exit with status EXIT_FAILURE if it
 139    appears to have been a stack overflow, or with a core dump
 140    otherwise.  This function is async-signal-safe.  */
 141
 142 void
 143 c_stack_die (int signo, siginfo_t *info, void *context)
 144 {
 145   char const *message =
 146     signo ? program_error_message : stack_overflow_message;
 147   write (STDERR_FILENO, program_name, strlen (program_name));
 148   write (STDERR_FILENO, ": ", 2);
 149   write (STDERR_FILENO, message, strlen (message));
 150   write (STDERR_FILENO, "\n", 1);
 151   if (! signo)
 152     _exit (exit_failure);
 153 #if HAVE_SIGINFO_T
 154   if (context && info && 0 <= info->si_code)
 155     {
 156       /* Re-raise the exception at the same address.  */
 157       char *addr = info->si_addr;
 158       *addr = 0;
 159     }
 160 #endif
 161   kill (getpid (), signo);
 162 }
 163
 164
 165 /* Set up ACTION so that it is invoked on C stack overflow.  Return -1
 166    (setting errno) if this cannot be done.
 167
 168    ACTION must invoke only async-signal-safe functions.  ACTION
 169    together with its callees must not require more than SIGSTKSZ bytes
 170    of stack space.  */
 171
 172 int
 173 c_stack_action (void (*action) (int, siginfo_t *, void *))
 174 {
 175 #if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
 176   errno = ENOTSUP;
 177   return -1;
 178 #else
 179   struct sigaction act;
 180   stack_t st;
 181   int r;
 182
 183   st.ss_flags = 0;
 184   st.ss_sp = alternate_signal_stack.buffer;
 185   st.ss_size = sizeof alternate_signal_stack.buffer;
 186   r = sigaltstack (&st, 0);
 187   if (r != 0)
 188     return r;
 189
 190   program_error_message = _("program error");
 191   stack_overflow_message = _("stack overflow");
 192   segv_action = action;
 193
 194   sigemptyset (&act.sa_mask);
 195
 196   /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but this
 197      is not true on Solaris 8 at least.  It doesn't hurt to use
 198      SA_NODEFER here, so leave it in.  */
 199   act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
 200
 201   act.sa_sigaction = segv_handler;
 202   return sigaction (SIGSEGV, &act, 0);
 203 #endif
 204 }
 205 \f
 206 #if DEBUG
 207
 208 #include <stdio.h>
 209
 210 int volatile exit_failure;
 211
 212 static long
 213 recurse (char *p)
 214 {
 215   char array[500];
 216   array[0] = 1;
 217   return *p + recurse (array);
 218 }
 219
 220 char *program_name;
 221
 222 int
 223 main (int argc, char **argv)
 224 {
 225   program_name = argv[0];
 226   c_stack_action (c_stack_die);
 227   return recurse ("\1");
 228 }
 229
 230 #endif /* DEBUG */
 231 \f
 232 /*
 233 Local Variables:
 234 compile-command: "gcc -D_GNU_SOURCE -DDEBUG \
 235   -DHAVE_INTTYPES_H -DHAVE_SIGINFO_T \
 236   -DHAVE_XSI_STACK_OVERFLOW_HEURISTIC -DHAVE_UNISTD_H \
 237   -Wall -W -g c-stack.c -o c-stack"
 238 End:
 239 */