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From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: aio_cancel segmentation fault for in progress write requests
Date: Fri, 7 Dec 2018 15:14:53 -0500	[thread overview]
Message-ID: <20181207201453.GH23599@brightrain.aerifal.cx> (raw)
In-Reply-To: <87h8fpaypx.fsf@oldenburg2.str.redhat.com>

On Fri, Dec 07, 2018 at 09:06:18PM +0100, Florian Weimer wrote:
> * Rich Felker:
> 
> > I don't think so. I'm concerned that it's a stack overflow, and that
> > somehow the kernel folks have managed to break the MINSIGSTKSZ ABI.
> 
> Probably:
> 
>   <https://sourceware.org/bugzilla/show_bug.cgi?id=20305>
>   <https://sourceware.org/bugzilla/show_bug.cgi?id=22636>
> 
> It's a nasty CPU backwards compatibility problem.  Some of the
> suggestions I made to work around this are simply wrong; don't take them
> too seriously.
> 
> Nowadays, the kernel has a way to disable the %zmm registers, but it
> unfortunately does not reduce the save area size.

How large is the saved context with the %zmm junk? I measured just
~768 bytes on normal x86_64 without it, and since 2048 is rounded up
to a whole page (4096), overflow should not happen until the signal
context is something like 3.5k (allowing ~512 bytes for TCB (~128) and
2 simple call frames).

Rich


  reply	other threads:[~2018-12-07 20:14 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-07 12:52 Arkadiusz Sienkiewicz
2018-12-07 15:44 ` Rich Felker
2018-12-07 16:04   ` Arkadiusz Sienkiewicz
2018-12-07 16:52     ` Orivej Desh
2018-12-07 16:52     ` Rich Felker
2018-12-07 17:31       ` A. Wilcox
2018-12-07 18:26         ` Rich Felker
2018-12-07 19:05           ` A. Wilcox
2018-12-07 20:07             ` Rich Felker
2018-12-07 19:13           ` A. Wilcox
2018-12-07 20:21             ` Rich Felker
2018-12-07 20:35             ` Markus Wichmann
2018-12-07 21:12               ` Rich Felker
2018-12-07 22:51               ` A. Wilcox
2018-12-07 23:50                 ` Rich Felker
2018-12-07 20:06           ` Florian Weimer
2018-12-07 20:14             ` Rich Felker [this message]
2018-12-08 16:18               ` Florian Weimer
2018-12-10  9:05                 ` Arkadiusz Sienkiewicz
2018-12-12  0:36                   ` Rich Felker
2018-12-17 14:21                     ` Arkadiusz Sienkiewicz
2018-12-17 17:29                       ` Rich Felker

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