Re: c-stack and Irix - libsigsegv

[Eric Blake]

Bruno Haible <bruno <at> clisp.org> writes:

> > Here's the minimal patch needed to CVS libsigsegv to expose the bug, as
> > well as work around it for Irix 5.3.
> 
> Nice work! I'm applying this only slightly modified version.
>   - In the configuration test, keep room to both sides of the ss_sp value.
>     On IRIX, we don't want the test to crash. We want it to exit(1) 
reasonably.

We need to do this consistently, then.  The subsequent configure check (whether 
longjmp works from a stack overflow handler) is needlessly falling foul of the 
Irix sigaltstack bug.

2008-09-23  Eric Blake  <address@hidden>

        Use 2 * SIGSTKSZ consistently in m4 checks.
        * m4/sigaltstack.m4 (SV_SIGALTSTACK): Work around Irix sigaltstack
        bug.
        * m4/sigaltstack-longjmp.m4 (SV_TRY_LEAVE_HANDLER_LONGJMP):
        Likewise.
        * m4/sigaltstack-siglongjmp.m4 (SV_TRY_LEAVE_HANDLER_SIGLONGJMP):
        Likewise.

Index: m4/sigaltstack-longjmp.m4
===================================================================
RCS file: /sources/libsigsegv/libsigsegv/m4/sigaltstack-longjmp.m4,v
retrieving revision 1.7
diff -u -p -r1.7 sigaltstack-longjmp.m4
--- m4/sigaltstack-longjmp.m4   24 Aug 2008 20:55:16 -0000      1.7
+++ m4/sigaltstack-longjmp.m4   23 Sep 2008 14:13:21 -0000
@@ -1,4 +1,4 @@
-# sigaltstack-longjmp.m4 serial 5 (libsigsegv-2.6)
+# sigaltstack-longjmp.m4 serial 6 (libsigsegv-2.6)
 dnl Copyright (C) 2002-2003, 2006, 2008 Bruno Haible <address@hidden>
 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
@@ -53,7 +53,7 @@ int recurse (volatile int n)
 }
 int main ()
 {
-  char mystack[SIGSTKSZ];
+  char mystack[2 * SIGSTKSZ];
   stack_t altstack;
   struct sigaction action;
   sigset_t emptyset;
@@ -65,9 +65,10 @@ int main ()
   rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */
   setrlimit (RLIMIT_STACK, &rl);
 #endif
-  /* Install the alternate stack.  */
-  altstack.ss_sp = mystack;
-  altstack.ss_size = sizeof (mystack);
+  /* Install the alternate stack.  Use midpoint to work around Irix
+     sigaltstack bug.  */
+  altstack.ss_sp = mystack + SIGSTKSZ;
+  altstack.ss_size = SIGSTKSZ;
   altstack.ss_flags = 0; /* no SS_DISABLE */
   if (sigaltstack (&altstack, NULL) < 0)
     exit (1);
Index: m4/sigaltstack-siglongjmp.m4
===================================================================
RCS file: /sources/libsigsegv/libsigsegv/m4/sigaltstack-siglongjmp.m4,v
retrieving revision 1.7
diff -u -p -r1.7 sigaltstack-siglongjmp.m4
--- m4/sigaltstack-siglongjmp.m4        24 Aug 2008 20:55:16 -0000      1.7
+++ m4/sigaltstack-siglongjmp.m4        23 Sep 2008 14:13:21 -0000
@@ -1,4 +1,4 @@
-# sigaltstack-siglongjmp.m4 serial 5 (libsigsegv-2.6)
+# sigaltstack-siglongjmp.m4 serial 6 (libsigsegv-2.6)
 dnl Copyright (C) 2002-2003, 2006, 2008 Bruno Haible <address@hidden>
 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
@@ -51,7 +51,7 @@ int recurse (volatile int n)
 }
 int main ()
 {
-  char mystack[SIGSTKSZ];
+  char mystack[2 * SIGSTKSZ];
   stack_t altstack;
   struct sigaction action;
 #ifdef __BEOS__
@@ -66,9 +66,10 @@ int main ()
   rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */
   setrlimit (RLIMIT_STACK, &rl);
 #endif
-  /* Install the alternate stack.  */
-  altstack.ss_sp = mystack;
-  altstack.ss_size = sizeof (mystack);
+  /* Install the alternate stack.  Use midpoint to work around Irix
+     sigaltstack bug.  */
+  altstack.ss_sp = mystack + SIGSTKSZ;
+  altstack.ss_size = SIGSTKSZ;
   altstack.ss_flags = 0; /* no SS_DISABLE */
   if (sigaltstack (&altstack, NULL) < 0)
     exit (1);
Index: m4/sigaltstack.m4
===================================================================
RCS file: /sources/libsigsegv/libsigsegv/m4/sigaltstack.m4,v
retrieving revision 1.12
diff -u -p -r1.12 sigaltstack.m4
--- m4/sigaltstack.m4   21 Sep 2008 13:41:28 -0000      1.12
+++ m4/sigaltstack.m4   23 Sep 2008 14:13:21 -0000
@@ -1,4 +1,4 @@
-# sigaltstack.m4 serial 9 (libsigsegv-2.7)
+# sigaltstack.m4 serial 10 (libsigsegv-2.7)
 dnl Copyright (C) 2002-2006, 2008 Bruno Haible <address@hidden>
 dnl Copyright (C) 2008 Eric Blake <address@hidden>
 dnl This file is free software, distributed under the terms of the GNU
@@ -74,7 +74,7 @@ int recurse (volatile int n)
 }
 int main ()
 {
-  char mystack[SIGSTKSZ];
+  char mystack[2 * SIGSTKSZ];
   stack_t altstack;
   struct sigaction action;
 #if defined HAVE_SETRLIMIT && defined RLIMIT_STACK
@@ -85,9 +85,10 @@ int main ()
   rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */
   setrlimit (RLIMIT_STACK, &rl);
 #endif
-  /* Install the alternate stack.  */
-  altstack.ss_sp = mystack;
-  altstack.ss_size = sizeof (mystack);
+  /* Install the alternate stack.  Use midpoint to work around Irix
+     sigaltstack bug.  */
+  altstack.ss_sp = mystack + SIGSTKSZ;
+  altstack.ss_size = SIGSTKSZ;
   altstack.ss_flags = 0; /* no SS_DISABLE */
   if (sigaltstack (&altstack, NULL) < 0)
     exit (1);