1 /* Stack overflow handling.
3 Copyright (C) 2002, 2004, 2006, 2008, 2009, 2010 Free Software Foundation,
6 This program is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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. */
41 # define __attribute__(x)
46 #define _(msgid) gettext (msgid)
51 #if ! HAVE_STACK_T && ! defined stack_t
52 typedef struct sigaltstack stack_t;
55 # define SIGSTKSZ 16384
56 #elif HAVE_LIBSIGSEGV && SIGSTKSZ < 16384
57 /* libsigsegv 2.6 through 2.8 have a bug where some architectures use
58 more than the Linux default of an 8k alternate stack when deciding
59 if a fault was caused by stack overflow. */
61 # define SIGSTKSZ 16384
67 /* Posix 2001 declares ucontext_t in <ucontext.h>, Posix 200x in
70 # include <ucontext.h>
81 #include "ignore-value.h"
83 #if defined SA_ONSTACK && defined SA_SIGINFO
84 # define SIGACTION_WORKS 1
86 # define SIGACTION_WORKS 0
92 extern char *program_name;
94 /* The user-specified action to take when a SEGV-related program error
95 or stack overflow occurs. */
96 static void (* volatile segv_action) (int);
98 /* Translated messages for program errors and stack overflow. Do not
99 translate them in the signal handler, since gettext is not
100 async-signal-safe. */
101 static char const * volatile program_error_message;
102 static char const * volatile stack_overflow_message;
104 /* Output an error message, then exit with status EXIT_FAILURE if it
105 appears to have been a stack overflow, or with a core dump
106 otherwise. This function is async-signal-safe. */
108 static void die (int) __attribute__ ((noreturn));
114 message = signo ? program_error_message : stack_overflow_message;
115 ignore_value (write (STDERR_FILENO, program_name, strlen (program_name)));
116 ignore_value (write (STDERR_FILENO, ": ", 2));
117 ignore_value (write (STDERR_FILENO, message, strlen (message)));
118 ignore_value (write (STDERR_FILENO, "\n", 1));
120 _exit (exit_failure);
125 #if (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK \
126 && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV
128 /* Storage for the alternate signal stack. */
131 char buffer[SIGSTKSZ];
133 /* These other members are for proper alignment. There's no
134 standard way to guarantee stack alignment, but this seems enough
139 } alternate_signal_stack;
142 null_action (int signo __attribute__ ((unused)))
146 #endif /* SIGALTSTACK || LIBSIGSEGV */
148 /* Only use libsigsegv if we need it; platforms like Solaris can
149 detect stack overflow without the overhead of an external
151 #if HAVE_LIBSIGSEGV && ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
153 /* Nonzero if general segv handler could not be installed. */
154 static volatile int segv_handler_missing;
156 /* Handle a segmentation violation and exit if it cannot be stack
157 overflow. This function is async-signal-safe. */
159 static int segv_handler (void *address __attribute__ ((unused)),
165 sprintf (buf, "segv_handler serious=%d\n", serious);
166 write (STDERR_FILENO, buf, strlen (buf));
170 /* If this fault is not serious, return 0 to let the stack overflow
171 handler take a shot at it. */
177 /* Handle a segmentation violation that is likely to be a stack
178 overflow and exit. This function is async-signal-safe. */
180 static void overflow_handler (int, stackoverflow_context_t)
181 __attribute__ ((noreturn));
183 overflow_handler (int emergency,
184 stackoverflow_context_t context __attribute__ ((unused)))
189 sprintf (buf, "overflow_handler emergency=%d segv_handler_missing=%d\n",
190 emergency, segv_handler_missing);
191 write (STDERR_FILENO, buf, strlen (buf));
195 die ((!emergency || segv_handler_missing) ? 0 : SIGSEGV);
199 c_stack_action (void (*action) (int))
201 segv_action = action ? action : null_action;
202 program_error_message = _("program error");
203 stack_overflow_message = _("stack overflow");
205 /* Always install the overflow handler. */
206 if (stackoverflow_install_handler (overflow_handler,
207 alternate_signal_stack.buffer,
208 sizeof alternate_signal_stack.buffer))
213 /* Try installing a general handler; if it fails, then treat all
214 segv as stack overflow. */
215 segv_handler_missing = sigsegv_install_handler (segv_handler);
219 #elif HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK && HAVE_STACK_OVERFLOW_HANDLING
221 /* Direction of the C runtime stack. This function is
222 async-signal-safe. */
225 # define find_stack_direction(ptr) STACK_DIRECTION
227 # if ! SIGACTION_WORKS || HAVE_XSI_STACK_OVERFLOW_HEURISTIC
229 find_stack_direction (char const *addr)
232 return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
239 /* Handle a segmentation violation and exit. This function is
240 async-signal-safe. */
242 static void segv_handler (int, siginfo_t *, void *) __attribute__((noreturn));
244 segv_handler (int signo, siginfo_t *info,
245 void *context __attribute__ ((unused)))
247 /* Clear SIGNO if it seems to have been a stack overflow. */
248 # if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
249 /* We can't easily determine whether it is a stack overflow; so
250 assume that the rest of our program is perfect (!) and that
251 this segmentation violation is a stack overflow.
253 Note that although both Linux and Solaris provide
254 sigaltstack, SA_ONSTACK, and SA_SIGINFO, currently only
255 Solaris satisfies the XSI heueristic. This is because
256 Solaris populates uc_stack with the details of the
257 interrupted stack, while Linux populates it with the details
258 of the current stack. */
261 if (0 < info->si_code)
263 /* If the faulting address is within the stack, or within one
264 page of the stack end, assume that it is a stack
266 ucontext_t const *user_context = context;
267 char const *stack_base = user_context->uc_stack.ss_sp;
268 size_t stack_size = user_context->uc_stack.ss_size;
269 char const *faulting_address = info->si_addr;
270 size_t s = faulting_address - stack_base;
271 size_t page_size = sysconf (_SC_PAGESIZE);
272 if (find_stack_direction (NULL) < 0)
274 if (s < stack_size + page_size)
281 "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
282 faulting_address, stack_base, (unsigned long) stack_size,
283 (unsigned long) page_size, signo);
284 write (STDERR_FILENO, buf, strlen (buf));
295 c_stack_action (void (*action) (int))
299 struct sigaction act;
301 # if SIGALTSTACK_SS_REVERSED
302 /* Irix mistakenly treats ss_sp as the upper bound, rather than
303 lower bound, of the alternate stack. */
304 st.ss_sp = alternate_signal_stack.buffer + SIGSTKSZ - sizeof (void *);
305 st.ss_size = sizeof alternate_signal_stack.buffer - sizeof (void *);
307 st.ss_sp = alternate_signal_stack.buffer;
308 st.ss_size = sizeof alternate_signal_stack.buffer;
310 r = sigaltstack (&st, NULL);
314 segv_action = action ? action : null_action;
315 program_error_message = _("program error");
316 stack_overflow_message = _("stack overflow");
318 sigemptyset (&act.sa_mask);
321 /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
322 this is not true on Solaris 8 at least. It doesn't hurt to use
323 SA_NODEFER here, so leave it in. */
324 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
325 act.sa_sigaction = segv_handler;
327 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND;
328 act.sa_handler = die;
331 # if FAULT_YIELDS_SIGBUS
332 if (sigaction (SIGBUS, &act, NULL) < 0)
335 return sigaction (SIGSEGV, &act, NULL);
338 #else /* ! ((HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
339 && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV) */
342 c_stack_action (void (*action) (int) __attribute__ ((unused)))