1 /* Stack overflow handling.
3 Copyright (C) 2002, 2004, 2006, 2008-2011 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 3 of the License, or
8 (at your option) any later version.
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, see <http://www.gnu.org/licenses/>. */
18 /* Written by Paul Eggert. */
22 A program that uses alloca, dynamic arrays, or large local
23 variables may extend the stack by more than a page at a time. If
24 so, when the stack overflows the operating system may not detect
25 the overflow until the program uses the array, and this module may
26 incorrectly report a program error instead of a stack overflow.
28 To avoid this problem, allocate only small objects on the stack; a
29 program should be OK if it limits single allocations to a page or
30 less. Allocate larger arrays in static storage, or on the heap
31 (e.g., with malloc). Yes, this is a pain, but we don't know of any
32 better solution that is portable.
34 No attempt has been made to deal with multithreaded applications. */
40 # define __attribute__(x)
45 #define _(msgid) gettext (msgid)
50 #if ! HAVE_STACK_T && ! defined stack_t
51 typedef struct sigaltstack stack_t;
54 # define SIGSTKSZ 16384
55 #elif HAVE_LIBSIGSEGV && SIGSTKSZ < 16384
56 /* libsigsegv 2.6 through 2.8 have a bug where some architectures use
57 more than the Linux default of an 8k alternate stack when deciding
58 if a fault was caused by stack overflow. */
60 # define SIGSTKSZ 16384
66 /* Posix 2001 declares ucontext_t in <ucontext.h>, Posix 200x in
69 # include <ucontext.h>
80 #include "ignore-value.h"
82 #if defined SA_ONSTACK && defined SA_SIGINFO
83 # define SIGINFO_WORKS 1
85 # define SIGINFO_WORKS 0
91 extern char *program_name;
93 /* The user-specified action to take when a SEGV-related program error
94 or stack overflow occurs. */
95 static void (* volatile segv_action) (int);
97 /* Translated messages for program errors and stack overflow. Do not
98 translate them in the signal handler, since gettext is not
100 static char const * volatile program_error_message;
101 static char const * volatile stack_overflow_message;
103 /* Output an error message, then exit with status EXIT_FAILURE if it
104 appears to have been a stack overflow, or with a core dump
105 otherwise. This function is async-signal-safe. */
107 static _Noreturn void
111 #if !SIGINFO_WORKS && !HAVE_LIBSIGSEGV
112 /* We can't easily determine whether it is a stack overflow; so
113 assume that the rest of our program is perfect (!) and that
114 this segmentation violation is a stack overflow. */
116 #endif /* !SIGINFO_WORKS && !HAVE_LIBSIGSEGV */
118 message = signo ? program_error_message : stack_overflow_message;
119 ignore_value (write (STDERR_FILENO, program_name, strlen (program_name)));
120 ignore_value (write (STDERR_FILENO, ": ", 2));
121 ignore_value (write (STDERR_FILENO, message, strlen (message)));
122 ignore_value (write (STDERR_FILENO, "\n", 1));
124 _exit (exit_failure);
129 #if (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK \
130 && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV
132 /* Storage for the alternate signal stack. */
135 char buffer[SIGSTKSZ];
137 /* These other members are for proper alignment. There's no
138 standard way to guarantee stack alignment, but this seems enough
143 } alternate_signal_stack;
146 null_action (int signo __attribute__ ((unused)))
150 #endif /* SIGALTSTACK || LIBSIGSEGV */
152 /* Only use libsigsegv if we need it; platforms like Solaris can
153 detect stack overflow without the overhead of an external
155 #if HAVE_LIBSIGSEGV && ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
157 /* Nonzero if general segv handler could not be installed. */
158 static volatile int segv_handler_missing;
160 /* Handle a segmentation violation and exit if it cannot be stack
161 overflow. This function is async-signal-safe. */
163 static int segv_handler (void *address __attribute__ ((unused)),
169 sprintf (buf, "segv_handler serious=%d\n", serious);
170 write (STDERR_FILENO, buf, strlen (buf));
174 /* If this fault is not serious, return 0 to let the stack overflow
175 handler take a shot at it. */
181 /* Handle a segmentation violation that is likely to be a stack
182 overflow and exit. This function is async-signal-safe. */
184 static _Noreturn void
185 overflow_handler (int emergency,
186 stackoverflow_context_t context __attribute__ ((unused)))
191 sprintf (buf, "overflow_handler emergency=%d segv_handler_missing=%d\n",
192 emergency, segv_handler_missing);
193 write (STDERR_FILENO, buf, strlen (buf));
197 die ((!emergency || segv_handler_missing) ? 0 : SIGSEGV);
201 c_stack_action (void (*action) (int))
203 segv_action = action ? action : null_action;
204 program_error_message = _("program error");
205 stack_overflow_message = _("stack overflow");
207 /* Always install the overflow handler. */
208 if (stackoverflow_install_handler (overflow_handler,
209 alternate_signal_stack.buffer,
210 sizeof alternate_signal_stack.buffer))
215 /* Try installing a general handler; if it fails, then treat all
216 segv as stack overflow. */
217 segv_handler_missing = sigsegv_install_handler (segv_handler);
221 #elif HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK && HAVE_STACK_OVERFLOW_HANDLING
225 /* Handle a segmentation violation and exit. This function is
226 async-signal-safe. */
228 static _Noreturn void
229 segv_handler (int signo, siginfo_t *info,
230 void *context __attribute__ ((unused)))
232 /* Clear SIGNO if it seems to have been a stack overflow. */
233 # if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
234 /* We can't easily determine whether it is a stack overflow; so
235 assume that the rest of our program is perfect (!) and that
236 this segmentation violation is a stack overflow.
238 Note that although both Linux and Solaris provide
239 sigaltstack, SA_ONSTACK, and SA_SIGINFO, currently only
240 Solaris satisfies the XSI heueristic. This is because
241 Solaris populates uc_stack with the details of the
242 interrupted stack, while Linux populates it with the details
243 of the current stack. */
246 if (0 < info->si_code)
248 /* If the faulting address is within the stack, or within one
249 page of the stack, assume that it is a stack overflow. */
250 ucontext_t const *user_context = context;
251 char const *stack_base = user_context->uc_stack.ss_sp;
252 size_t stack_size = user_context->uc_stack.ss_size;
253 char const *faulting_address = info->si_addr;
254 size_t page_size = sysconf (_SC_PAGESIZE);
255 size_t s = faulting_address - stack_base + page_size;
256 if (s < stack_size + 2 * page_size)
263 "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
264 faulting_address, stack_base, (unsigned long) stack_size,
265 (unsigned long) page_size, signo);
266 write (STDERR_FILENO, buf, strlen (buf));
277 c_stack_action (void (*action) (int))
281 struct sigaction act;
283 # if SIGALTSTACK_SS_REVERSED
284 /* Irix mistakenly treats ss_sp as the upper bound, rather than
285 lower bound, of the alternate stack. */
286 st.ss_sp = alternate_signal_stack.buffer + SIGSTKSZ - sizeof (void *);
287 st.ss_size = sizeof alternate_signal_stack.buffer - sizeof (void *);
289 st.ss_sp = alternate_signal_stack.buffer;
290 st.ss_size = sizeof alternate_signal_stack.buffer;
292 r = sigaltstack (&st, NULL);
296 segv_action = action ? action : null_action;
297 program_error_message = _("program error");
298 stack_overflow_message = _("stack overflow");
300 sigemptyset (&act.sa_mask);
303 /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
304 this is not true on Solaris 8 at least. It doesn't hurt to use
305 SA_NODEFER here, so leave it in. */
306 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
307 act.sa_sigaction = segv_handler;
309 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND;
310 act.sa_handler = die;
313 # if FAULT_YIELDS_SIGBUS
314 if (sigaction (SIGBUS, &act, NULL) < 0)
317 return sigaction (SIGSEGV, &act, NULL);
320 #else /* ! ((HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
321 && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV) */
324 c_stack_action (void (*action) (int) __attribute__ ((unused)))