contrib/diffutils-2.8/lib/c-stack.c

   1 /* Stack overflow handling.
   2
   3    Copyright (C) 2002, 2004 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 /* NOTES:
  22
  23    A program that uses alloca, dynamic arrays, or large local
  24    variables may extend the stack by more than a page at a time.  If
  25    so, when the stack overflows the operating system may not detect
  26    the overflow until the program uses the array, and this module may
  27    incorrectly report a program error instead of a stack overflow.
  28
  29    To avoid this problem, allocate only small objects on the stack; a
  30    program should be OK if it limits single allocations to a page or
  31    less.  Allocate larger arrays in static storage, or on the heap
  32    (e.g., with malloc).  Yes, this is a pain, but we don't know of any
  33    better solution that is portable.
  34
  35    No attempt has been made to deal with multithreaded applications.  */
  36
  37 #if HAVE_CONFIG_H
  38 # include <config.h>
  39 #endif
  40
  41 #ifndef __attribute__
  42 # if __GNUC__ < 3 || __STRICT_ANSI__
  43 #  define __attribute__(x)
  44 # endif
  45 #endif
  46
  47 #include "gettext.h"
  48 #define _(msgid) gettext (msgid)
  49
  50 #include <errno.h>
  51 #ifndef ENOTSUP
  52 # define ENOTSUP EINVAL
  53 #endif
  54 #ifndef EOVERFLOW
  55 # define EOVERFLOW EINVAL
  56 #endif
  57
  58 #include <signal.h>
  59 #if ! HAVE_STACK_T && ! defined stack_t
  60 typedef struct sigaltstack stack_t;
  61 #endif
  62
  63 #include <stdlib.h>
  64 #include <string.h>
  65
  66 #if HAVE_SYS_RESOURCE_H
  67 /* Include sys/time.h here, because...
  68    SunOS-4.1.x <sys/resource.h> fails to include <sys/time.h>.
  69    This gives "incomplete type" errors for ru_utime and tu_stime.  */
  70 # if HAVE_SYS_TIME_H
  71 #  include <sys/time.h>
  72 # endif
  73 # include <sys/resource.h>
  74 #endif
  75
  76 #if HAVE_UCONTEXT_H
  77 # include <ucontext.h>
  78 #endif
  79
  80 #if HAVE_UNISTD_H
  81 # include <unistd.h>
  82 #endif
  83 #ifndef STDERR_FILENO
  84 # define STDERR_FILENO 2
  85 #endif
  86
  87 #if DEBUG
  88 # include <stdio.h>
  89 #endif
  90
  91 #include "c-stack.h"
  92 #include "exitfail.h"
  93
  94 #if (HAVE_STRUCT_SIGACTION_SA_SIGACTION && defined SA_NODEFER \
  95      && defined SA_ONSTACK && defined SA_RESETHAND && defined SA_SIGINFO)
  96 # define SIGACTION_WORKS 1
  97 #else
  98 # define SIGACTION_WORKS 0
  99 #endif
 100
 101 extern char *program_name;
 102
 103 /* The user-specified action to take when a SEGV-related program error
 104    or stack overflow occurs.  */
 105 static void (* volatile segv_action) (int);
 106
 107 /* Translated messages for program errors and stack overflow.  Do not
 108    translate them in the signal handler, since gettext is not
 109    async-signal-safe.  */
 110 static char const * volatile program_error_message;
 111 static char const * volatile stack_overflow_message;
 112
 113 /* Output an error message, then exit with status EXIT_FAILURE if it
 114    appears to have been a stack overflow, or with a core dump
 115    otherwise.  This function is async-signal-safe.  */
 116
 117 static void die (int) __attribute__ ((noreturn));
 118 static void
 119 die (int signo)
 120 {
 121   char const *message;
 122   segv_action (signo);
 123   message = signo ? program_error_message : stack_overflow_message;
 124   write (STDERR_FILENO, program_name, strlen (program_name));
 125   write (STDERR_FILENO, ": ", 2);
 126   write (STDERR_FILENO, message, strlen (message));
 127   write (STDERR_FILENO, "\n", 1);
 128   if (! signo)
 129     _exit (exit_failure);
 130   kill (getpid (), signo);
 131   abort ();
 132 }
 133
 134 #if HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
 135
 136 /* Direction of the C runtime stack.  This function is
 137    async-signal-safe.  */
 138
 139 # if STACK_DIRECTION
 140 #  define find_stack_direction(ptr) STACK_DIRECTION
 141 # else
 142 static int
 143 find_stack_direction (char const *addr)
 144 {
 145   char dummy;
 146   return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
 147 }
 148 # endif
 149
 150 /* Storage for the alternate signal stack.  */
 151 static union
 152 {
 153   char buffer[SIGSTKSZ];
 154
 155   /* These other members are for proper alignment.  There's no
 156      standard way to guarantee stack alignment, but this seems enough
 157      in practice.  */
 158   long double ld;
 159   long l;
 160   void *p;
 161 } alternate_signal_stack;
 162
 163 # if SIGACTION_WORKS
 164
 165 /* Handle a segmentation violation and exit.  This function is
 166    async-signal-safe.  */
 167
 168 static void segv_handler (int, siginfo_t *, void *) __attribute__((noreturn));
 169 static void
 170 segv_handler (int signo, siginfo_t *info,
 171               void *context __attribute__ ((unused)))
 172 {
 173   /* Clear SIGNO if it seems to have been a stack overflow.  */
 174   if (0 < info->si_code)
 175     {
 176 #  if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
 177       /* We can't easily determine whether it is a stack overflow; so
 178          assume that the rest of our program is perfect (!) and that
 179          this segmentation violation is a stack overflow.  */
 180       signo = 0;
 181 #  else
 182       /* If the faulting address is within the stack, or within one
 183          page of the stack end, assume that it is a stack
 184          overflow.  */
 185       ucontext_t const *user_context = context;
 186       char const *stack_base = user_context->uc_stack.ss_sp;
 187       size_t stack_size = user_context->uc_stack.ss_size;
 188       char const *faulting_address = info->si_addr;
 189       size_t s = faulting_address - stack_base;
 190       size_t page_size = sysconf (_SC_PAGESIZE);
 191       if (find_stack_direction (0) < 0)
 192         s += page_size;
 193       if (s < stack_size + page_size)
 194         signo = 0;
 195
 196 #   if DEBUG
 197       {
 198         char buf[1024];
 199         sprintf (buf,
 200                  "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
 201                  faulting_address, stack_base, (unsigned long) stack_size,
 202                  (unsigned long) page_size, signo);
 203         write (STDERR_FILENO, buf, strlen (buf));
 204       }
 205 #   endif
 206 #  endif
 207     }
 208
 209   die (signo);
 210 }
 211 # endif
 212
 213 static void
 214 null_action (int signo __attribute__ ((unused)))
 215 {
 216 }
 217
 218 /* Set up ACTION so that it is invoked on C stack overflow.  Return -1
 219    (setting errno) if this cannot be done.
 220
 221    When ACTION is called, it is passed an argument equal to SIGSEGV
 222    for a segmentation violation that does not appear related to stack
 223    overflow, and is passed zero otherwise.  On many platforms it is
 224    hard to tell; when in doubt, zero is passed.
 225
 226    A null ACTION acts like an action that does nothing.
 227
 228    ACTION must be async-signal-safe.  ACTION together with its callees
 229    must not require more than SIGSTKSZ bytes of stack space.  */
 230
 231 int
 232 c_stack_action (void (*action) (int))
 233 {
 234   int r;
 235   stack_t st;
 236   st.ss_flags = 0;
 237   st.ss_sp = alternate_signal_stack.buffer;
 238   st.ss_size = sizeof alternate_signal_stack.buffer;
 239   r = sigaltstack (&st, 0);
 240   if (r != 0)
 241     return r;
 242
 243   segv_action = action ? action : null_action;
 244   program_error_message = _("program error");
 245   stack_overflow_message = _("stack overflow");
 246
 247   {
 248 # if SIGACTION_WORKS
 249     struct sigaction act;
 250     sigemptyset (&act.sa_mask);
 251
 252     /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
 253        this is not true on Solaris 8 at least.  It doesn't hurt to use
 254        SA_NODEFER here, so leave it in.  */
 255     act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
 256
 257     act.sa_sigaction = segv_handler;
 258
 259     return sigaction (SIGSEGV, &act, 0);
 260 # else
 261     return signal (SIGSEGV, die) == SIG_ERR ? -1 : 0;
 262 # endif
 263   }
 264 }
 265
 266 #else /* ! (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) */
 267
 268 int
 269 c_stack_action (void (*action) (int)  __attribute__ ((unused)))
 270 {
 271   errno = ENOTSUP;
 272   return -1;
 273 }
 274
 275 #endif
 276
 277 \f
 278
 279 #if DEBUG
 280
 281 int volatile exit_failure;
 282
 283 static long
 284 recurse (char *p)
 285 {
 286   char array[500];
 287   array[0] = 1;
 288   return *p + recurse (array);
 289 }
 290
 291 char *program_name;
 292
 293 int
 294 main (int argc __attribute__ ((unused)), char **argv)
 295 {
 296   program_name = argv[0];
 297   fprintf (stderr,
 298            "The last output line should contain \"stack overflow\".\n");
 299   if (c_stack_action (0) == 0)
 300     return recurse ("\1");
 301   perror ("c_stack_action");
 302   return 1;
 303 }
 304
 305 #endif /* DEBUG */
 306 \f
 307 /*
 308 Local Variables:
 309 compile-command: "gcc -DDEBUG -DHAVE_CONFIG_H -I.. -g -O -Wall -W c-stack.c"
 310 End:
 311 */