From owner-freebsd-current@freebsd.org Tue Oct 31 19:37:40 2017 Return-Path: Delivered-To: freebsd-current@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 6B4D5E61CE1 for ; Tue, 31 Oct 2017 19:37:40 +0000 (UTC) (envelope-from andreast-list@fgznet.ch) Received: from smtp.fgznet.ch (smtp.fgznet.ch [IPv6:2001:4060:1:1001::14:52]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 2769C1F89; Tue, 31 Oct 2017 19:37:39 +0000 (UTC) (envelope-from andreast-list@fgznet.ch) Received: from [192.168.225.14] (dhclient-91-190-10-49.flashcable.ch [91.190.10.49]) (using TLSv1 with cipher ECDHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by fgznet.ch (Postfix) with ESMTPSA id 64E44C51EC; Tue, 31 Oct 2017 20:37:29 +0100 (CET) Subject: Re: Segfault in _Unwind_* code called from pthread_exit To: Konstantin Belousov , Tijl Coosemans Cc: freebsd-current@FreeBSD.org, gerald@FreeBSD.org References: <20170824180830.199885b0@kalimero.tijl.coosemans.org> <20170825173851.09116ddc@kalimero.tijl.coosemans.org> <20170825234442.GO1700@kib.kiev.ua> <20170826202813.1240a1ef@kalimero.tijl.coosemans.org> <20170826184034.GR1700@kib.kiev.ua> <20171029182351.502f53cf@kalimero.tijl.coosemans.org> <20171029191358.GU2566@kib.kiev.ua> <9a724da4-70f1-4330-9a77-619739008a14@fgznet.ch> <20171030153207.15a42a1e@kalimero.tijl.coosemans.org> <9468430e-fda4-10f4-b6a0-aa40d7d64f5b@fgznet.ch> <20171031092803.GA2566@kib.kiev.ua> From: Andreas Tobler Message-ID: <9619a1f8-bb42-abc9-a4ee-3b93192f365e@fgznet.ch> Date: Tue, 31 Oct 2017 20:37:29 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20171031092803.GA2566@kib.kiev.ua> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: de-CH Content-Transfer-Encoding: 7bit X-Scanned-By: Obelix Submit on 127.0.1.1 X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 31 Oct 2017 19:37:40 -0000 On 31.10.17 10:28, Konstantin Belousov wrote: > On Mon, Oct 30, 2017 at 10:54:05PM +0100, Andreas Tobler wrote: >> On 30.10.17 15:32, Tijl Coosemans wrote: >>> On Sun, 29 Oct 2017 20:40:46 +0100 Andreas Tobler wrote: >>>> Attached what I have for libgcc. It can be applied to gcc5-8, should >>>> give no issues. The mentioned tc from this thread and mine, >>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82635 do pass. >>>> >>>> What do you think? >>> >>> Like I said before the return address can be anything. It could for >>> instance point to some instruction in a random function and then the >>> stack unwinder will think thread_start was called from that function. >>> There's no check you can add to libgcc to distinguish that from a >>> normal valid return address. >>> >> Maybe not, and most probably I do not understand what is happening. But >> with my modification I survive the test case. >> >> If no objections from your or Konstantin's side come up I will commit it >> to the gcc repo. It will not 'fix' the issue, but it will improve the >> gcc behavior. > > I posted something similar when the discussion thread started. From the > cursory look, your patch is better than mine. The only difference that > makes me wonder is that I used #ifdef KERN_PROC_SIGTRAMP around the > block because I believe gcc has more relaxed policy about supporting > obsoleted OS versions. I am aware about KERN_PROC_SIGTRAMP and older OS releases, that's why I asked for feedback. Do we, FreeBSD'ers, want to have gcc unwind support on older than FreeBSD 9.3 releases? I think the gcc folks do not care, but we are the ones who might have an need for such a support? @Gerald, do you have an opinion? I can 'ifdef' the new code and in the 'else' case we fall back to the already existing path. Thank you both for the feedback. Andreas