sigsegv: New module.

* lib/sigsegv.in.h: New file, from GNU libsigsegv with modifications. * lib/sigsegv.c: Likewise. * lib/stackvma.h: Likewise. * lib/stackvma.c: Likewise. * m4/sigaltstack.m4: Likewise. * m4/stack-direction.m4: Likewise. * modules/sigsegv: New file.
2026-05-13 15:13:36 +00:00 · 2021-05-16 15:20:12 +02:00
parent 1a72950760
commit e54aa61969
8 changed files with 4143 additions and 0 deletions
--- a/11
+++ b/11
@@ -1,3 +1,14 @@
+2021-05-16  Bruno Haible  <bruno@clisp.org>
+
+	sigsegv: New module.
+	* lib/sigsegv.in.h: New file, from GNU libsigsegv with modifications.
+	* lib/sigsegv.c: Likewise.
+	* lib/stackvma.h: Likewise.
+	* lib/stackvma.c: Likewise.
+	* m4/sigaltstack.m4: Likewise.
+	* m4/stack-direction.m4: Likewise.
+	* modules/sigsegv: New file.
+
 2021-05-15  Pádraig Brady  <P@draigBrady.com>

 	realloc-gnu: avoid glibc MALLOC_CHECK_ issue
--- a/lib/sigsegv.c
+++ b/lib/sigsegv.c
--- a/lib/sigsegv.in.h
+++ b/lib/sigsegv.in.h
@@ -0,0 +1,233 @@
+/* Page fault handling library.
+   Copyright (C) 1998-2021  Bruno Haible <bruno@clisp.org>
+
+   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 of the License, 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, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SIGSEGV_H
+#define _SIGSEGV_H
+
+/* Get size_t.  */
+#include <stddef.h>
+
+/* Define the fault context structure.  */
+#if defined __linux__ || defined __ANDROID__ \
+    || (defined __FreeBSD__ && (defined __arm__ || defined __armhf__ || defined __arm64__)) \
+    || defined __NetBSD__ \
+    || defined _AIX || defined __sun \
+    || defined __CYGWIN__
+/* Linux, FreeBSD, NetBSD, AIX, Solaris, Cygwin */
+# include <ucontext.h>
+#elif (defined __APPLE__ && defined __MACH__)
+/* macOS */
+# include <sys/ucontext.h>
+#elif defined __HAIKU__
+/* Haiku */
+# include <signal.h>
+#endif
+
+/* Correct the value of SIGSTKSZ on some systems.
+   AIX 64-bit: original value 4096 is too small.
+   HP-UX: original value 8192 is too small.
+   Solaris 11/x86_64: original value 8192 is too small.  */
+#if defined _AIX && defined _ARCH_PPC64
+# include <signal.h>
+# undef SIGSTKSZ
+# define SIGSTKSZ 8192
+#endif
+#if defined __hpux || (defined __sun && (defined __x86_64__ || defined __amd64__))
+# include <signal.h>
+# undef SIGSTKSZ
+# define SIGSTKSZ 16384
+#endif
+
+/* HAVE_SIGSEGV_RECOVERY
+   is defined if the system supports catching SIGSEGV.  */
+#if defined __linux__ || defined __ANDROID__ || defined __GNU__ \
+    || defined __FreeBSD_kernel__ || (defined __FreeBSD__ && !(defined __sparc__ || defined __sparc64__)) || defined __DragonFly__ \
+    || defined __NetBSD__ \
+    || defined __OpenBSD__ \
+    || (defined __APPLE__ && defined __MACH__) \
+    || defined _AIX || defined __sgi || defined __sun \
+    || defined __CYGWIN__ || defined __HAIKU__
+/* Linux, Hurd, GNU/kFreeBSD, FreeBSD, NetBSD, OpenBSD, macOS, AIX, IRIX, Solaris, Cygwin, Haiku */
+# define HAVE_SIGSEGV_RECOVERY 1
+#endif
+
+/* HAVE_STACK_OVERFLOW_RECOVERY
+   is defined if stack overflow can be caught.  */
+#if defined __linux__ || defined __ANDROID__ || defined __GNU__ \
+    || defined __FreeBSD_kernel__ || (defined __FreeBSD__ && !(defined __sparc__ || defined __sparc64__)) || defined __DragonFly__ \
+    || (defined __NetBSD__ && !(defined __sparc__ || defined __sparc64__)) \
+    || defined __OpenBSD__ \
+    || (defined __APPLE__ && defined __MACH__) \
+    || defined _AIX || defined __sgi || defined __sun \
+    || defined __CYGWIN__ || defined __HAIKU__
+/* Linux, Hurd, GNU/kFreeBSD, FreeBSD, NetBSD, OpenBSD, macOS, AIX, IRIX, Solaris, Cygwin, Haiku */
+# define HAVE_STACK_OVERFLOW_RECOVERY 1
+#endif
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define LIBSIGSEGV_VERSION 0x020D    /* version number: (major<<8) + minor */
+extern int libsigsegv_version;       /* Likewise */
+
+/* -------------------------------------------------------------------------- */
+
+#if 1 /* really only HAVE_SIGSEGV_RECOVERY */
+
+/*
+ * The mask of bits that are set to zero in a fault address that gets passed
+ * to a global SIGSEGV handler.
+ * On some platforms, the precise fault address is not known, only the memory
+ * page into which the fault address falls. This is apparently allowed by POSIX:
+ * <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/signal.h.html>
+ * says: "For some implementations, the value of si_addr may be inaccurate."
+ * In this case, the returned fault address is rounded down to a multiple of
+ * getpagesize() = sysconf(_SC_PAGESIZE).
+ * On such platforms, we define SIGSEGV_FAULT_ADDRESS_ALIGNMENT to be an upper
+ * bound for getpagesize() (and, like getpagesize(), also a power of 2).
+ * On the platforms where the returned fault address is the precise one, we
+ * define SIGSEGV_FAULT_ADDRESS_ALIGNMENT to 1.
+ */
+# if defined __NetBSD__ && (defined __sparc__ || defined __sparc64__)
+  /* getpagesize () is 0x1000 or 0x2000, depending on hardware.  */
+#  define SIGSEGV_FAULT_ADDRESS_ALIGNMENT 0x2000UL
+# elif defined __linux__ && (defined __s390__ || defined __s390x__)
+  /* getpagesize () is 0x1000.  */
+#  define SIGSEGV_FAULT_ADDRESS_ALIGNMENT 0x1000UL
+# else
+#  define SIGSEGV_FAULT_ADDRESS_ALIGNMENT 1UL
+# endif
+
+/*
+ * The type of a global SIGSEGV handler.
+ * The fault address, with the bits (SIGSEGV_FAULT_ADDRESS_ALIGNMENT - 1)
+ * cleared, is passed as argument.
+ * The access type (read access or write access) is not passed; your handler
+ * has to know itself how to distinguish these two cases.
+ * The second argument is 0, meaning it could also be a stack overflow, or 1,
+ * meaning the handler should seriously try to fix the fault.
+ * The return value should be nonzero if the handler has done its job
+ * and no other handler should be called, or 0 if the handler declines
+ * responsibility for the given address.
+ *
+ * The handler is run at a moment when nothing about the global state of the
+ * program is known. Therefore it cannot use facilities that manipulate global
+ * variables or locks. In particular, it cannot use malloc(); use mmap()
+ * instead. It cannot use fopen(); use open() instead. Etc. All global
+ * variables that are accessed by the handler should be marked 'volatile'.
+ */
+typedef int (*sigsegv_handler_t) (void* fault_address, int serious);
+
+/*
+ * Installs a global SIGSEGV handler.
+ * This should be called once only, and it ignores any previously installed
+ * SIGSEGV handler.
+ * Returns 0 on success, or -1 if the system doesn't support catching SIGSEGV.
+ */
+extern int sigsegv_install_handler (sigsegv_handler_t handler);
+
+/*
+ * Deinstalls the global SIGSEGV handler.
+ * This goes back to the state where no SIGSEGV handler is installed.
+ */
+extern void sigsegv_deinstall_handler (void);
+
+/*
+ * Prepares leaving a SIGSEGV handler (through longjmp or similar means).
+ * Control is transferred by calling CONTINUATION with CONT_ARG1, CONT_ARG2,
+ * CONT_ARG3 as arguments.
+ * CONTINUATION must not return.
+ * The sigsegv_leave_handler function may return if called from a SIGSEGV
+ * handler; its return value should be used as the handler's return value.
+ * The sigsegv_leave_handler function does not return if called from a
+ * stack overflow handler.
+ */
+extern int sigsegv_leave_handler (void (*continuation) (void*, void*, void*), void* cont_arg1, void* cont_arg2, void* cont_arg3);
+
+#endif /* HAVE_SIGSEGV_RECOVERY */
+
+#if 1 /* really only HAVE_STACK_OVERFLOW_RECOVERY */
+
+/*
+ * The type of a context passed to a stack overflow handler.
+ * This type is system dependent; on some platforms it is an 'ucontext_t *',
+ * on some platforms it is a 'struct sigcontext *', on others merely an
+ * opaque 'void *'.
+ */
+# if defined __linux__ || defined __ANDROID__ \
+     || (defined __FreeBSD__ && (defined __arm__ || defined __armhf__ || defined __arm64__)) \
+     || defined __NetBSD__ \
+     || (defined __APPLE__ && defined __MACH__) \
+     || defined _AIX || defined __sun \
+     || defined __CYGWIN__ || defined __HAIKU__
+typedef ucontext_t *stackoverflow_context_t;
+# elif defined __GNU__ \
+       || defined __FreeBSD_kernel__ || (defined __FreeBSD__ && !(defined __sparc__ || defined __sparc64__)) \
+       || defined __OpenBSD__ || defined __sgi
+typedef struct sigcontext *stackoverflow_context_t;
+# else
+typedef void *stackoverflow_context_t;
+# endif
+
+/*
+ * The type of a stack overflow handler.
+ * Such a handler should perform a longjmp call in order to reduce the amount
+ * of stack needed. It must not return.
+ * The emergency argument is 0 when the stack could be repared, or 1 if the
+ * application should better save its state and exit now.
+ *
+ * The handler is run at a moment when nothing about the global state of the
+ * program is known. Therefore it cannot use facilities that manipulate global
+ * variables or locks. In particular, it cannot use malloc(); use mmap()
+ * instead. It cannot use fopen(); use open() instead. Etc. All global
+ * variables that are accessed by the handler should be marked 'volatile'.
+ */
+typedef void (*stackoverflow_handler_t) (int emergency, stackoverflow_context_t scp);
+
+/*
+ * Installs a stack overflow handler.
+ * The extra_stack argument is a pointer to a pre-allocated area used as a
+ * stack for executing the handler. It typically comes from a static variable
+ * or from heap-allocated memoty; placing it on the main stack may fail on
+ * some operating systems.
+ * Its size, passed in extra_stack_size, should be sufficiently large.  The
+ * following code determines an appropriate size:
+ *   #include <signal.h>
+ *   #ifndef SIGSTKSZ         / * glibc defines SIGSTKSZ for this purpose * /
+ *   # define SIGSTKSZ 16384  / * on most platforms, 16 KB are sufficient * /
+ *   #endif
+ * Returns 0 on success, or -1 if the system doesn't support catching stack
+ * overflow.
+ */
+extern int stackoverflow_install_handler (stackoverflow_handler_t handler,
+                                          void* extra_stack, size_t extra_stack_size);
+
+/*
+ * Deinstalls the stack overflow handler.
+ */
+extern void stackoverflow_deinstall_handler (void);
+
+#endif /* HAVE_STACK_OVERFLOW_RECOVERY */
+
+/* -------------------------------------------------------------------------- */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _SIGSEGV_H */
--- a/lib/stackvma.c
+++ b/lib/stackvma.c
--- a/lib/stackvma.h
+++ b/lib/stackvma.h
@@ -0,0 +1,60 @@
+/* Determine the virtual memory area of a given address.
+   Copyright (C) 2002-2021  Bruno Haible <bruno@clisp.org>
+   Copyright (C) 2003-2006  Paolo Bonzini <bonzini@gnu.org>
+
+   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 of the License, 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, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _STACKVMA_H
+#define _STACKVMA_H
+
+#include <stdint.h>
+
+/* Describes a virtual memory area, with some info about the gap between
+   it and the next or previous virtual memory area.  */
+struct vma_struct
+{
+  uintptr_t start;
+  uintptr_t end;
+#if STACK_DIRECTION < 0
+  /* Info about the gap between this VMA and the previous one.
+     addr must be < vma->start.  */
+  int (*is_near_this) (uintptr_t addr, struct vma_struct *vma);
+  /* Private field, not provided by all sigsegv_get_vma implementations.  */
+  uintptr_t prev_end;
+#endif
+#if STACK_DIRECTION > 0
+  /* Info about the gap between this VMA and the next one.
+     addr must be > vma->end - 1.  */
+  int (*is_near_this) (uintptr_t addr, struct vma_struct *vma);
+  /* Private field, not provided by all sigsegv_get_vma implementations.  */
+  uintptr_t next_start;
+#endif
+};
+
+/* Determines the virtual memory area to which a given address belongs,
+   and returns 0.  Returns -1 if it cannot be determined.
+   This function is used to determine the stack extent when a fault occurs.  */
+extern int sigsegv_get_vma (uintptr_t address, struct vma_struct *vma);
+
+/* Defined if sigsegv_get_vma actually works (i.e. does not always fail).  */
+#if defined __linux__ || defined __ANDROID__ \
+    || defined __FreeBSD_kernel__ || defined __FreeBSD__ || defined __DragonFly__ \
+    || defined __NetBSD__ || defined __OpenBSD__ \
+    || (defined __APPLE__ && defined __MACH__) \
+    || defined _AIX || defined __sgi || defined __sun \
+    || defined __CYGWIN__ || defined __HAIKU__
+# define HAVE_STACKVMA 1
+#endif
+
+#endif /* _STACKVMA_H */
--- a/m4/sigaltstack.m4
+++ b/m4/sigaltstack.m4
@@ -0,0 +1,198 @@
+# sigaltstack.m4 serial 12
+dnl Copyright (C) 2002-2021 Bruno Haible <bruno@clisp.org>
+dnl Copyright (C) 2008 Eric Blake <ebb9@byu.net>
+dnl This file is free software, distributed under the terms of the GNU
+dnl General Public License.  As a special exception to the GNU General
+dnl Public License, this file may be distributed as part of a program
+dnl that contains a configuration script generated by Autoconf, under
+dnl the same distribution terms as the rest of that program.
+
+AC_DEFUN([SV_SIGALTSTACK],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+
+  AC_CHECK_FUNCS_ONCE([sigaltstack setrlimit])
+
+  if test "$ac_cv_func_sigaltstack" = yes; then
+    AC_CHECK_TYPE([stack_t], ,
+      [AC_DEFINE(stack_t, [struct sigaltstack],
+         [Define to 'struct sigaltstack' if that's the type of the argument to sigaltstack])
+      ],
+      [
+#include <signal.h>
+#if HAVE_SYS_SIGNAL_H
+# include <sys/signal.h>
+#endif
+      ])
+  fi
+
+  AC_CACHE_CHECK([for working sigaltstack], [sv_cv_sigaltstack], [
+    if test "$ac_cv_func_sigaltstack" = yes; then
+      case "$host_os" in
+        macos* | darwin[[6-9]]* | darwin[[1-9]][[0-9]]*)
+          # On MacOS X 10.2 or newer, just assume that if it compiles, it will
+          # work. If we were to perform the real test, 1 Crash Report dialog
+          # window would pop up.
+          AC_LINK_IFELSE([
+            AC_LANG_PROGRAM([[#include <signal.h>]],
+              [[int x = SA_ONSTACK; stack_t ss; sigaltstack ((stack_t*)0, &ss);]])],
+            [sv_cv_sigaltstack="guessing yes"],
+            [sv_cv_sigaltstack=no])
+          ;;
+        *)
+          AC_RUN_IFELSE([
+            AC_LANG_SOURCE([[
+#include <stdlib.h>
+#include <signal.h>
+#if HAVE_SYS_SIGNAL_H
+# include <sys/signal.h>
+#endif
+#if HAVE_SETRLIMIT
+# include <sys/types.h>
+# include <sys/time.h>
+# include <sys/resource.h>
+#endif
+#ifndef SIGSTKSZ
+# define SIGSTKSZ 16384
+#endif
+void stackoverflow_handler (int sig)
+{
+  /* If we get here, the stack overflow was caught.  */
+  exit (0);
+}
+volatile int * recurse_1 (volatile int n, volatile int *p)
+{
+  if (n >= 0)
+    *recurse_1 (n + 1, p) += n;
+  return p;
+}
+int recurse (volatile int n)
+{
+  int sum = 0;
+  return *recurse_1 (n, &sum);
+}
+char mystack[2 * SIGSTKSZ];
+int main ()
+{
+  stack_t altstack;
+  struct sigaction action;
+#if defined 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
+  /* Install the alternate stack.  Use the midpoint of mystack, to guard
+     against a buggy interpretation of ss_sp on IRIX.  */
+  altstack.ss_sp = mystack + SIGSTKSZ;
+  altstack.ss_size = SIGSTKSZ;
+  altstack.ss_flags = 0; /* no SS_DISABLE */
+  if (sigaltstack (&altstack, NULL) < 0)
+    exit (1);
+  /* Install the SIGSEGV handler.  */
+  sigemptyset (&action.sa_mask);
+  action.sa_handler = &stackoverflow_handler;
+  action.sa_flags = SA_ONSTACK;
+  sigaction (SIGSEGV, &action, (struct sigaction *) NULL);
+  sigaction (SIGBUS, &action, (struct sigaction *) NULL);
+  /* Provoke a stack overflow.  */
+  recurse (0);
+  exit (2);
+}]])],
+            [sv_cv_sigaltstack=yes],
+            [sv_cv_sigaltstack=no],
+            [
+              dnl FIXME: Put in some more known values here.
+              case "$host_os" in
+                *)
+                  AC_LINK_IFELSE([
+                    AC_LANG_PROGRAM([[#include <signal.h>]],
+                      [[int x = SA_ONSTACK; stack_t ss; sigaltstack ((stack_t*)0, &ss);]])],
+                    [sv_cv_sigaltstack="guessing yes"],
+                    [sv_cv_sigaltstack=no])
+                  ;;
+              esac
+            ])
+          ;;
+      esac
+    else
+      sv_cv_sigaltstack=no
+    fi
+  ])
+  if test "$sv_cv_sigaltstack" != no; then
+    AC_DEFINE([HAVE_WORKING_SIGALTSTACK], [1],
+      [Define if you have the sigaltstack() function and it works.])
+
+    dnl The ss_sp field of a stack_t is, according to POSIX, the lowest address
+    dnl of the memory block designated as an alternate stack. But IRIX 5.3
+    dnl interprets it as the highest address!
+    AC_CACHE_CHECK([for correct stack_t interpretation],
+      [sv_cv_sigaltstack_low_base], [
+      AC_RUN_IFELSE([
+        AC_LANG_SOURCE([[
+#include <stdlib.h>
+#include <signal.h>
+#if HAVE_SYS_SIGNAL_H
+# include <sys/signal.h>
+#endif
+#ifndef SIGSTKSZ
+# define SIGSTKSZ 16384
+#endif
+volatile char *stack_lower_bound;
+volatile char *stack_upper_bound;
+static void check_stack_location (volatile char *addr)
+{
+  if (addr >= stack_lower_bound && addr <= stack_upper_bound)
+    exit (0);
+  else
+    exit (1);
+}
+static void stackoverflow_handler (int sig)
+{
+  char dummy;
+  check_stack_location (&dummy);
+}
+int main ()
+{
+  char mystack[2 * SIGSTKSZ];
+  stack_t altstack;
+  struct sigaction action;
+  /* Install the alternate stack.  */
+  altstack.ss_sp = mystack + SIGSTKSZ;
+  altstack.ss_size = SIGSTKSZ;
+  stack_lower_bound = (char *) altstack.ss_sp;
+  stack_upper_bound = (char *) altstack.ss_sp + altstack.ss_size - 1;
+  altstack.ss_flags = 0; /* no SS_DISABLE */
+  if (sigaltstack (&altstack, NULL) < 0)
+    exit (2);
+  /* Install the SIGSEGV handler.  */
+  sigemptyset (&action.sa_mask);
+  action.sa_handler = &stackoverflow_handler;
+  action.sa_flags = SA_ONSTACK;
+  if (sigaction (SIGSEGV, &action, (struct sigaction *) NULL) < 0)
+    exit(3);
+  /* Provoke a SIGSEGV.  */
+  raise (SIGSEGV);
+  exit (3);
+}]])],
+      [sv_cv_sigaltstack_low_base=yes],
+      [sv_cv_sigaltstack_low_base=no],
+      [
+        dnl FIXME: Put in some more known values here.
+        case "$host_os" in
+          irix5*) sv_cv_sigaltstack_low_base="no" ;;
+          *)      sv_cv_sigaltstack_low_base="guessing yes" ;;
+        esac
+      ])
+    ])
+    if test "$sv_cv_sigaltstack_low_base" = no; then
+      AC_DEFINE([SIGALTSTACK_SS_REVERSED], [1],
+        [Define if sigaltstack() interprets the stack_t.ss_sp field incorrectly,
+         as the highest address of the alternate stack range rather than as the
+         lowest address.])
+    fi
+  fi
+])
--- a/m4/stack-direction.m4
+++ b/m4/stack-direction.m4
@@ -0,0 +1,104 @@
+# stack-direction.m4 serial 6
+dnl Copyright (C) 2002-2021 Bruno Haible <bruno@clisp.org>
+dnl Copyright (C) 2002-2021 Free Software Foundation, Inc.
+dnl This file is free software, distributed under the terms of the GNU
+dnl General Public License.  As a special exception to the GNU General
+dnl Public License, this file may be distributed as part of a program
+dnl that contains a configuration script generated by Autoconf, under
+dnl the same distribution terms as the rest of that program.
+
+# Determine the stack direction. Define the C macro STACK_DIRECTION.
+AC_DEFUN([SV_STACK_DIRECTION],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_CACHE_CHECK([for stack direction], [sv_cv_stack_direction_msg], [
+    case "$host_cpu" in
+      dnl See the #define STACK_GROWS_DOWNWARD in gcc-3.1/gcc/config/*/*.h.
+      a29k | \
+      aarch64* | \
+      alpha* | \
+      arc | \
+      arm* | strongarm* | xscale* | \
+      avr | avr32 | \
+      bfin | \
+      c1 | c2 | c32 | c34 | c38 | \
+      clipper | \
+      cris | \
+      d30v | \
+      elxsi | \
+      fr30 | \
+      h8300 | \
+      i?86 | x86_64 | \
+      i860 | \
+      ia64 | \
+      m32r | \
+      m68* | \
+      m88k | \
+      mcore | \
+      microblaze | \
+      mips* | \
+      mmix | \
+      mn10200 | \
+      mn10300 | \
+      nios2 | \
+      nds32* | \
+      ns32k | \
+      pdp11 | \
+      pj* | \
+      powerpc* | rs6000 | \
+      riscv* | \
+      romp | \
+      s390* | \
+      sh* | \
+      sparc* | \
+      v850 | \
+      vax | \
+      xtensa)
+        sv_cv_stack_direction=-1 ;;
+      c4x | \
+      dsp16xx | \
+      i960 | \
+      hppa* | parisc* | \
+      stormy16 | \
+      we32k)
+        sv_cv_stack_direction=1 ;;
+      *)
+        if test $cross_compiling = no; then
+          cat > conftest.c <<EOF
+#include <stdio.h>
+int
+find_stack_direction (int *addr, int depth)
+{
+  int dir, dummy = 0;
+  if (! addr)
+    addr = &dummy;
+  *addr = addr < &dummy ? 1 : addr == &dummy ? 0 : -1;
+  dir = depth ? find_stack_direction (addr, depth - 1) : 0;
+  return dir + dummy;
+}
+int
+main (int argc, char *argv[])
+{
+  printf ("%d\n", find_stack_direction (NULL, argc + 20));
+  return 0;
+}
+EOF
+          AC_TRY_EVAL([ac_link])
+          sv_cv_stack_direction=`./conftest`
+        else
+          sv_cv_stack_direction=0
+        fi
+        ;;
+    esac
+    case $sv_cv_stack_direction in
+      1)  sv_cv_stack_direction_msg="grows up";;
+      -1) sv_cv_stack_direction_msg="grows down";;
+      *)  sv_cv_stack_direction_msg="unknown";;
+    esac
+  ])
+  AC_DEFINE_UNQUOTED([STACK_DIRECTION], [$sv_cv_stack_direction],
+    [Define as the direction of stack growth for your system.
+     STACK_DIRECTION > 0 => grows toward higher addresses
+     STACK_DIRECTION < 0 => grows toward lower addresses
+     STACK_DIRECTION = 0 => spaghetti stack.])
+])
--- a/modules/sigsegv
+++ b/modules/sigsegv
@@ -0,0 +1,101 @@
+Description:
+A simplified variant of GNU libsigsegv.
+It implements the most important features of GNU libsigsegv: catching SIGSEGV
+and catching stack overflow. It does *not* implement the 'sigsegv_dispatcher'
+type (which is not multithread-safe).
+It supports all modern Unix-like platforms: Linux, Hurd, FreeBSD, NetBSD,
+OpenBSD, macOS, AIX, Solaris, Cygwin, Haiku, even IRIX. It does *not* support
+HP-UX, Minix, native Windows; on these platforms the module compiles and
+provides a <sigsegv.h> header file, but it does not define HAVE_SIGSEGV_RECOVERY
+and HAVE_STACK_OVERFLOW_RECOVERY.
+Unlike GNU libsigsegv, which consists of many .h and .c files, this module
+compiles to just two object files, rather than a library.
+
+Files:
+lib/sigsegv.in.h
+lib/sigsegv.c
+lib/stackvma.h
+lib/stackvma.c
+m4/mmap-anon.m4
+m4/sigaltstack.m4
+m4/stack-direction.m4
+m4/libsigsegv.m4
+
+Depends-on:
+havelib
+host-cpu-c-abi
+stdint
+getpagesize
+
+configure.ac:
+AC_ARG_WITH([libsigsegv],
+  [AS_HELP_STRING([--with-libsigsegv],
+     [use the GNU libsigsegv library, when present, instead of the gnulib module 'sigsegv'])])
+SIGSEGV_H=sigsegv.h
+if test "$with_libsigsegv" = yes; then
+  gl_LIBSIGSEGV
+  if test "$gl_cv_lib_sigsegv" = yes; then
+    SIGSEGV_H=
+  fi
+fi
+AC_SUBST([SIGSEGV_H])
+AM_CONDITIONAL([GL_GENERATE_SIGSEGV_H], [test -n "$SIGSEGV_H"])
+if test -n "$SIGSEGV_H"; then
+  dnl Persuade glibc <sys/ucontext.h> to declare macros designating register
+  dnl indices: REG_RSP on x86_64, REG_ESP on i386.
+  dnl Persuade Solaris OpenIndiana <ucontext.h> to include <sys/regset.h>,
+  dnl which declares macros designating register indices, such as ESP on i386.
+  dnl Persuade Solaris OpenIndiana <unistd.h> to declare mincore().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  case "$host_os" in
+    solaris2.11)
+      AC_DEFINE([SOLARIS11], [1], [Define on Solaris 11 and its derivates.])
+      ;;
+  esac
+
+  gl_FUNC_MMAP_ANON
+
+  dnl Stack direction.
+  SV_STACK_DIRECTION
+
+  dnl Catching stack overflow requires an alternate signal stack.
+  dnl The old "install a guard page" trick would be unreliable, because
+  dnl we don't know where exactly to place the guard page.
+  SV_SIGALTSTACK
+
+  AC_CHECK_FUNCS_ONCE([getrlimit])
+fi
+
+Makefile.am:
+BUILT_SOURCES += $(SIGSEGV_H)
+
+if GL_GENERATE_SIGSEGV_H
+sigsegv.h: sigsegv.in.h $(top_builddir)/config.status
+	$(AM_V_GEN)rm -f $@-t $@ && \
+	{ echo '/* DO NOT EDIT! GENERATED AUTOMATICALLY! */'; \
+	  cat $(srcdir)/sigsegv.in.h; \
+	} > $@-t && \
+	mv $@-t $@
+else
+sigsegv.h: $(top_builddir)/config.status
+	rm -f $@
+endif
+MOSTLYCLEANFILES += sigsegv.h sigsegv.h-t
+
+if GL_GENERATE_SIGSEGV_H
+lib_SOURCES += sigsegv.c stackvma.c
+endif
+
+Include:
+<sigsegv.h>
+
+Link:
+$(LTLIBSIGSEGV) when linking with libtool, $(LIBSIGSEGV) otherwise
+
+License:
+GPLv2+
+
+Maintainer:
+Bruno Haible