Date: Tue, 31 Oct 2017 20:37:29 +0100 From: Andreas Tobler <andreast-list@fgznet.ch> To: Konstantin Belousov <kostikbel@gmail.com>, Tijl Coosemans <tijl@FreeBSD.org> Cc: freebsd-current@FreeBSD.org, gerald@FreeBSD.org Subject: Re: Segfault in _Unwind_* code called from pthread_exit Message-ID: <9619a1f8-bb42-abc9-a4ee-3b93192f365e@fgznet.ch> In-Reply-To: <20171031092803.GA2566@kib.kiev.ua> 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>
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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 <andreast-list@fgznet.ch> 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
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