This is the mail archive of the
cygwin
mailing list for the Cygwin project.
Re: libsigsegv progress: SIGSEGV and siginfo_t.si_addr
- From: Christopher Faylor <cgf-use-the-mailinglist-please at cygwin dot com>
- To: cygwin at cygwin dot com
- Date: Wed, 22 Jul 2009 18:26:47 -0400
- Subject: Re: libsigsegv progress: SIGSEGV and siginfo_t.si_addr
- References: <loom.20090722T211710-662@post.gmane.org>
- Reply-to: cygwin at cygwin dot com
On Wed, Jul 22, 2009 at 09:18:57PM +0000, Eric Blake wrote:
>POSIX requires that for SIGSEGV and SIGBUS, the si_addr member of siginfo_t be
>set to the memory address where access failed, and not the address of the
>instruction attempting to access that address (for SIGILL and SIGFPE, the
>si_addr field is correct, and for all other signals, the si_addr is unspecified
>by POSIX so it might as well be the faulting instruction).
>
>Fixing si_addr to contain the correct information will make it possible to
>patch libsigsegv to avoid installing an SEH handler for all but stack
>overflow. (Without this patch, I think I can still patch libsigsegv to honor
>SIGSEGV, but it will be a much bigger hack of still installing a libsigsegv SEH
>handler that sniffs the faulting address, then in the SIGSEGV handler refers to
>the address that was sniffed).
>
>2009-07-22 Eric Blake <ebb9@byu.net>
>
> * exceptions.cc (handle_exceptions): Set si_addr according to
> POSIX for SIGSEGV.
>
>diff --git a/winsup/cygwin/exceptions.cc b/winsup/cygwin/exceptions.cc
>index 7663285..df02489 100644
>--- a/winsup/cygwin/exceptions.cc
>+++ b/winsup/cygwin/exceptions.cc
>@@ -686,7 +686,8 @@ _cygtls::handle_exceptions (EXCEPTION_RECORD *e,
>exception_list *frame, CONTEXT
> me.signal_exit (0x80 | si.si_signo); // Flag signal + core dump
> }
>
>- si.si_addr = (void *) in->Eip;
>+ si.si_addr = (si.si_signo == SIGSEGV || si.si_signo == SIGBUS
>+ ? (void *) e->ExceptionInformation[1] : (void *) in->Eip);
> si.si_errno = si.si_pid = si.si_uid = 0;
> me.incyg++;
> sig_send (NULL, si, &me); // Signal myself
Looks ok. Please check in.
Thanks for the patch.
cgf
--
Problem reports: http://cygwin.com/problems.html
FAQ: http://cygwin.com/faq/
Documentation: http://cygwin.com/docs.html
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple