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 64extern 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. */ 72static 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 91static int 92find_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. */ 100static void (* volatile segv_action) (int, siginfo_t *, void *); 101 102/* Handle a segmentation violation and exit. This function is 103 async-signal-safe. */ 104 105static void 106segv_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. */ 135static char const * volatile program_error_message; 136static 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 142void 143c_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 172int 173c_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} 205 206#if DEBUG 207 208#include <stdio.h> 209 210int volatile exit_failure; 211 212static long 213recurse (char *p) 214{ 215 char array[500]; 216 array[0] = 1; 217 return *p + recurse (array); 218} 219 220char *program_name; 221 222int 223main (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 */ 231 232/* 233Local Variables: 234compile-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" 238End: 239*/ 240