X-Spam-Check-By: sourceware.org Date: Wed, 29 Mar 2006 18:15:34 -0500 From: Christopher Faylor To: cygwin AT cygwin DOT com Subject: Re: dlopen() bug (new testcase) Message-ID: <20060329231534.GC12890@trixie.casa.cgf.cx> Reply-To: cygwin AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com References: <469704026 AT web DOT de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <469704026@web.de> User-Agent: Mutt/1.5.11 Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm Precedence: bulk List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id k2TNFgvB020220 On Thu, Mar 30, 2006 at 01:10:56AM +0200, Bernhard Loos wrote: >I looked at the problem again this week, but unfortunately I'm unable >to debug anything happening after the first SIGSEGV. I inserted a view >OutputDebugString()-calls and got those results: > >00:00:00.703: LoadLibraryA("H:\cygwin\test\CrashTest\CrashTest.dll") called from "CYGWIN1.DLL" at address 0x6100FE42 by thread 1. >00:00:00.718: Loaded "CRASHTEST.DLL" at address 0x003F0000 by thread 1. Successfully hooked module. >00:00:00.718: DllMain(0x003F0000, DLL_PROCESS_ATTACH, 0x00000000) in "CRASHTEST.DLL" called by thread 1. >00:00:00.718: myfault::faulted >00:00:00.718: setup_fault >00:00:00.718: First chance exception 0xC0000005 (Access Violation) occurred in "CYGWIN1.DLL" at address 0x610B2DE2 by thread 1. >00:00:00.718: Unloaded "CRASHTEST.DLL" at address 0x003F0000 by thread 1. >00:00:00.718: LoadLibraryA("H:\cygwin\test\CrashTest\CrashTest.dll") returned NULL by thread 1. Error: Unzulssiger Zugriff auf einen Speicherbereich (998). >00:00:00.781: First chance exception 0xC0000005 (Access Violation) occurred at address 0x003F101A by thread 1. >00:00:00.781: return_from_fault >00:00:00.781: First chance exception 0xC0000005 (Access Violation) occurred at address 0x40000060 by thread 1. >00:00:00.781: First chance exception 0xC0000029 (Unknown) occurred in "NTDLL.DLL" at address 0x7C95EB28 by thread 1. > >It looks, like Windows unloads the DLL after the first exception even before the myfault-exception handler is able to catch it. >So return_from_fault() tries to longjmp to code wich isn't present any more an the second exception occurs. > >To fix this problem, I would suggest to use the IsBadReadPtr()-function instead of the myfault-exception handler to check the pointer in >verifyable_object_isvalid(). >I could write a patch, if nobody has any objections. Sorry, no. We *just* got rid of IsBadReadPtr's. FWIW, I doubt that Windows is really ignoring an exception handler. cgf -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/