# Check prerequisites for compiling lib/c-stack.c. # Copyright (C) 2002, 2003, 2004, 2008 Free Software Foundation, Inc. # This file is free software; the Free Software Foundation # gives unlimited permission to copy and/or distribute it, # with or without modifications, as long as this notice is preserved. # Written by Paul Eggert. # serial 6 AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC], [# for STACK_DIRECTION AC_REQUIRE([AC_FUNC_ALLOCA]) AC_CHECK_FUNCS_ONCE([setrlimit]) AC_CHECK_HEADERS_ONCE([ucontext.h]) AC_CACHE_CHECK([for working C stack overflow detection], [ac_cv_sys_stack_overflow_works], [AC_TRY_RUN( [ #include #include #if HAVE_SETRLIMIT # include # include # include #endif #ifndef SIGSTKSZ # define SIGSTKSZ 16384 #endif static union { char buffer[SIGSTKSZ]; long double ld; long u; void *p; } alternate_signal_stack; static void segv_handler (int signo) { _exit (0); } static int c_stack_action () { 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; act.sa_handler = segv_handler; return sigaction (SIGSEGV, &act, 0); } static int recurse (char *p) { char array[500]; array[0] = 1; return *p + recurse (array); } int main () { #if HAVE_SETRLIMIT && defined RLIMIT_STACK /* Before starting the endless recursion, try to be friendly to the user's machine. On some Linux 2.2.x systems, there is no stack limit for user processes at all. We don't want to kill such systems. */ struct rlimit rl; rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */ setrlimit (RLIMIT_STACK, &rl); #endif return c_stack_action () || recurse ("\1"); } ], [ac_cv_sys_stack_overflow_works=yes], [ac_cv_sys_stack_overflow_works=no], [ac_cv_sys_stack_overflow_works=cross-compiling])]) if test $ac_cv_sys_stack_overflow_works = yes; then AC_DEFINE([HAVE_STACK_OVERFLOW_HANDLING], [1], [Define to 1 if extending the stack slightly past the limit causes a SIGSEGV which can be handled on an alternate stack established with sigaltstack.]) AC_CACHE_CHECK([for precise C stack overflow detection], ac_cv_sys_xsi_stack_overflow_heuristic, [AC_TRY_RUN( [ #include #include #if HAVE_UCONTEXT_H # include #endif #if HAVE_SETRLIMIT # include # include # include #endif #ifndef SIGSTKSZ # define SIGSTKSZ 16384 #endif static union { char buffer[SIGSTKSZ]; long double ld; long 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) { /* For XSI heuristics to work, we need uc_stack to describe the interrupted stack (as on Solaris), and not the currently executing stack (as on Linux). */ 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 () { 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 () { #if HAVE_SETRLIMIT && defined RLIMIT_STACK /* Before starting the endless recursion, try to be friendly to the user's machine. On some Linux 2.2.x systems, there is no stack limit for user processes at all. We don't want to kill such systems. */ struct rlimit rl; rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */ setrlimit (RLIMIT_STACK, &rl); #endif return c_stack_action () || 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 $ac_cv_sys_xsi_stack_overflow_heuristic = yes; then AC_DEFINE(HAVE_XSI_STACK_OVERFLOW_HEURISTIC, 1, [Define to 1 if extending the stack slightly past the limit causes a SIGSEGV, and an alternate stack can be established with sigaltstack, and the signal handler is passed a context that specifies the run time stack. This behavior is defined by POSIX 1003.1-2001 with the X/Open System Interface (XSI) option and is a standardized way to implement a SEGV-based stack overflow detection heuristic.]) fi fi]) AC_DEFUN([gl_PREREQ_C_STACK], [AC_REQUIRE([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC]) AC_REQUIRE([gl_LIBSIGSEGV]) # for STACK_DIRECTION AC_REQUIRE([AC_FUNC_ALLOCA]) AC_CHECK_FUNCS_ONCE([sigaltstack]) AC_CHECK_DECLS([sigaltstack], , , [#include ]) AC_CHECK_HEADERS_ONCE([unistd.h ucontext.h]) AC_CHECK_TYPES([stack_t], , , [#include ]) dnl c-stack does not need -lsigsegv if the system has XSI heuristics. if test "$gl_cv_lib_sigsegv" = yes \ && test $"ac_cv_sys_xsi_stack_overflow_heuristic" != yes ; then AC_SUBST([LIBCSTACK], [$LIBSIGSEGV]) AC_SUBST([LTLIBCSTACK], [$LTLIBSIGSEGV]) fi ]) AC_DEFUN([gl_C_STACK], [ dnl Prerequisites of lib/c-stack.c. gl_PREREQ_C_STACK ])