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From:	Eric Blake <ebb9 AT byu DOT net>
Subject:	libsigsegv progress: SIGSEGV and =?utf-8?b?c2lnaW5mb190LnNpX2FkZHI=?=
Date:	Wed, 22 Jul 2009 21:18:57 +0000 (UTC)
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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 AT byu DOT 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




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