1 /* Stack overflow handling.
3 Copyright (C) 2002, 2004, 2006 Free Software Foundation, Inc.
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)
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.
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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
19 /* Written by Paul Eggert. */
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.
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.
35 No attempt has been made to deal with multithreaded applications. */
40 # if __GNUC__ < 3 || __STRICT_ANSI__
41 # define __attribute__(x)
46 #define _(msgid) gettext (msgid)
50 # define ENOTSUP EINVAL
53 # define EOVERFLOW EINVAL
57 #if ! HAVE_STACK_T && ! defined stack_t
58 typedef struct sigaltstack stack_t;
64 #if HAVE_SYS_RESOURCE_H
65 /* Include sys/time.h here, because...
66 SunOS-4.1.x <sys/resource.h> fails to include <sys/time.h>.
67 This gives "incomplete type" errors for ru_utime and tu_stime. */
69 # include <sys/time.h>
71 # include <sys/resource.h>
75 # include <ucontext.h>
80 # define STDERR_FILENO 2
90 #if (HAVE_STRUCT_SIGACTION_SA_SIGACTION && defined SA_NODEFER \
91 && defined SA_ONSTACK && defined SA_RESETHAND && defined SA_SIGINFO)
92 # define SIGACTION_WORKS 1
94 # define SIGACTION_WORKS 0
97 extern char *program_name;
99 /* The user-specified action to take when a SEGV-related program error
100 or stack overflow occurs. */
101 static void (* volatile segv_action) (int);
103 /* Translated messages for program errors and stack overflow. Do not
104 translate them in the signal handler, since gettext is not
105 async-signal-safe. */
106 static char const * volatile program_error_message;
107 static char const * volatile stack_overflow_message;
109 /* Output an error message, then exit with status EXIT_FAILURE if it
110 appears to have been a stack overflow, or with a core dump
111 otherwise. This function is async-signal-safe. */
113 static void die (int) __attribute__ ((noreturn));
119 message = signo ? program_error_message : stack_overflow_message;
120 write (STDERR_FILENO, program_name, strlen (program_name));
121 write (STDERR_FILENO, ": ", 2);
122 write (STDERR_FILENO, message, strlen (message));
123 write (STDERR_FILENO, "\n", 1);
125 _exit (exit_failure);
126 kill (getpid (), signo);
130 #if HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
132 /* Direction of the C runtime stack. This function is
133 async-signal-safe. */
136 # define find_stack_direction(ptr) STACK_DIRECTION
139 find_stack_direction (char const *addr)
142 return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
146 /* Storage for the alternate signal stack. */
149 char buffer[SIGSTKSZ];
151 /* These other members are for proper alignment. There's no
152 standard way to guarantee stack alignment, but this seems enough
157 } alternate_signal_stack;
161 /* Handle a segmentation violation and exit. This function is
162 async-signal-safe. */
164 static void segv_handler (int, siginfo_t *, void *) __attribute__((noreturn));
166 segv_handler (int signo, siginfo_t *info,
167 void *context __attribute__ ((unused)))
169 /* Clear SIGNO if it seems to have been a stack overflow. */
170 if (0 < info->si_code)
172 # if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
173 /* We can't easily determine whether it is a stack overflow; so
174 assume that the rest of our program is perfect (!) and that
175 this segmentation violation is a stack overflow. */
178 /* If the faulting address is within the stack, or within one
179 page of the stack end, assume that it is a stack
181 ucontext_t const *user_context = context;
182 char const *stack_base = user_context->uc_stack.ss_sp;
183 size_t stack_size = user_context->uc_stack.ss_size;
184 char const *faulting_address = info->si_addr;
185 size_t s = faulting_address - stack_base;
186 size_t page_size = sysconf (_SC_PAGESIZE);
187 if (find_stack_direction (0) < 0)
189 if (s < stack_size + page_size)
196 "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
197 faulting_address, stack_base, (unsigned long) stack_size,
198 (unsigned long) page_size, signo);
199 write (STDERR_FILENO, buf, strlen (buf));
210 null_action (int signo __attribute__ ((unused)))
214 /* Set up ACTION so that it is invoked on C stack overflow. Return -1
215 (setting errno) if this cannot be done.
217 When ACTION is called, it is passed an argument equal to SIGSEGV
218 for a segmentation violation that does not appear related to stack
219 overflow, and is passed zero otherwise. On many platforms it is
220 hard to tell; when in doubt, zero is passed.
222 A null ACTION acts like an action that does nothing.
224 ACTION must be async-signal-safe. ACTION together with its callees
225 must not require more than SIGSTKSZ bytes of stack space. */
228 c_stack_action (void (*action) (int))
233 st.ss_sp = alternate_signal_stack.buffer;
234 st.ss_size = sizeof alternate_signal_stack.buffer;
235 r = sigaltstack (&st, 0);
239 segv_action = action ? action : null_action;
240 program_error_message = _("program error");
241 stack_overflow_message = _("stack overflow");
245 struct sigaction act;
246 sigemptyset (&act.sa_mask);
248 /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
249 this is not true on Solaris 8 at least. It doesn't hurt to use
250 SA_NODEFER here, so leave it in. */
251 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
253 act.sa_sigaction = segv_handler;
255 return sigaction (SIGSEGV, &act, 0);
257 return signal (SIGSEGV, die) == SIG_ERR ? -1 : 0;
262 #else /* ! (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) */
265 c_stack_action (void (*action) (int) __attribute__ ((unused)))
277 int volatile exit_failure;
284 return *p + recurse (array);
290 main (int argc __attribute__ ((unused)), char **argv)
292 program_name = argv[0];
294 "The last output line should contain \"stack overflow\".\n");
295 if (c_stack_action (0) == 0)
296 return recurse ("\1");
297 perror ("c_stack_action");
305 compile-command: "gcc -DDEBUG -g -O -Wall -W c-stack.c"