Date: Tue, 31 Oct 2017 11:28:03 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Andreas Tobler <andreast-list@fgznet.ch> Cc: Tijl Coosemans <tijl@FreeBSD.org>, freebsd-current@FreeBSD.org, gerald@FreeBSD.org Subject: Re: Segfault in _Unwind_* code called from pthread_exit Message-ID: <20171031092803.GA2566@kib.kiev.ua> In-Reply-To: <9468430e-fda4-10f4-b6a0-aa40d7d64f5b@fgznet.ch> 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>
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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.
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