# Check prerequisites for compiling lib/c-stack.c. # Copyright (C) 2002 Free Software Foundation, Inc. # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2, or (at your option) # any later version. # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA # 02111-1307, USA. AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC], [# for STACK_DIRECTION AC_REQUIRE([AC_FUNC_ALLOCA]) AC_CACHE_CHECK([for working C stack overflow detection], ac_cv_sys_xsi_stack_overflow_heuristic, [AC_TRY_RUN( [ #include #include static union { char buffer[SIGSTKSZ]; long double ld; uintmax_t u; void *p; } alternate_signal_stack; #if STACK_DIRECTION # define find_stack_direction(ptr) STACK_DIRECTION #else static int find_stack_direction (char const *addr) { char dummy; return (! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1); } #endif static void segv_handler (int signo, siginfo_t *info, void *context) { if (0 < info->si_code) { ucontext_t const *user_context = context; char const *stack_min = user_context->uc_stack.ss_sp; size_t stack_size = user_context->uc_stack.ss_size; char const *faulting_address = info->si_addr; size_t s = faulting_address - stack_min; size_t page_size = sysconf (_SC_PAGESIZE); if (find_stack_direction (0) < 0) s += page_size; if (s < stack_size + page_size) _exit (0); } _exit (1); } static int c_stack_action (void) { stack_t st; struct sigaction act; int r; st.ss_flags = 0; st.ss_sp = alternate_signal_stack.buffer; st.ss_size = sizeof alternate_signal_stack.buffer; r = sigaltstack (&st, 0); if (r != 0) return r; sigemptyset (&act.sa_mask); act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO; act.sa_sigaction = segv_handler; return sigaction (SIGSEGV, &act, 0); } static int recurse (char *p) { char array[500]; array[0] = 1; return *p + recurse (array); } int main (void) { c_stack_action (); return recurse ("\1"); } ], [ac_cv_sys_xsi_stack_overflow_heuristic=yes], [ac_cv_sys_xsi_stack_overflow_heuristic=no], [ac_cv_sys_xsi_stack_overflow_heuristic=cross-compiling])]) if test $ac_cv_sys_xsi_stack_overflow_heuristic = yes; then AC_DEFINE(HAVE_XSI_STACK_OVERFLOW_HEURISTIC, 1, [Define to 1 if extending the stack slightly past the limit causes a SIGSEGV, and an alternate stack can be established with sigaltstack, and the signal handler is passed a context that specifies the run time stack. This behavior is defined by POSIX 1003.1-2001 with the X/Open System Interface (XSI) option and is a standardized way to implement a SEGV-based stack overflow detection heuristic.]) fi]) AC_DEFUN([jm_PREREQ_C_STACK], [AC_REQUIRE([jm_AC_TYPE_UINTMAX_T]) AC_REQUIRE([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC]) # for STACK_DIRECTION AC_REQUIRE([AC_FUNC_ALLOCA]) AC_CHECK_HEADERS(unistd.h) AC_CHECK_TYPES([siginfo_t, stack_t], , , [#include ])])