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# 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 5
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 <unistd.h>
#include <signal.h>
#if HAVE_SETRLIMIT
# include <sys/types.h>
# include <sys/time.h>
# include <sys/resource.h>
#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
c_stack_action ();
return 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 <unistd.h>
#include <signal.h>
#if HAVE_UCONTEXT_H
# include <ucontext.h>
#endif
#if HAVE_SETRLIMIT
# include <sys/types.h>
# include <sys/time.h>
# include <sys/resource.h>
#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
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 $ac_cv_sys_xsi_stack_overflow_heuristic = yes; then
AC_DEFINE(HAVE_XSI_STACK_OVERFLOW_HEURISTIC, 1,
[Define to 1 if extending the stack slightly past the limit causes
a SIGSEGV, and an alternate stack can be established with sigaltstack,
and the signal handler is passed a context that specifies the
run time stack. This behavior is defined by POSIX 1003.1-2001
with the X/Open System Interface (XSI) option
and is a standardized way to implement a SEGV-based stack
overflow detection heuristic.])
fi
fi])
AC_DEFUN([gl_PREREQ_C_STACK],
[AC_REQUIRE([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC])
AC_REQUIRE([gl_LIBSIGSEGV])
# for STACK_DIRECTION
AC_REQUIRE([AC_FUNC_ALLOCA])
AC_CHECK_FUNCS_ONCE([sigaltstack])
AC_CHECK_DECLS([sigaltstack], , , [#include <signal.h>])
AC_CHECK_HEADERS_ONCE([unistd.h ucontext.h])
AC_CHECK_TYPES([stack_t], , , [#include <signal.h>])
dnl c-stack does not need -lsigsegv if the system has XSI heuristics.
if test "$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
])
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