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From: Thomas Huth <thuth@redhat.com>
To: Florian Weimer <fweimer@redhat.com>,
	gcc@gcc.gnu.org, libc-alpha@sourceware.org,
	qemu-devel@nongnu.org
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
	Iain Sandoe <idsandoe@googlemail.com>
Subject: Re: Disabling TLS address caching to help QEMU on GNU/Linux
Date: Wed, 21 Jul 2021 09:22:24 +0200	[thread overview]
Message-ID: <c9ce99db-874b-03c2-9561-be9b59bd1988@redhat.com> (raw)
In-Reply-To: <87im15qbp3.fsf@oldenburg.str.redhat.com>

On 20/07/2021 16.52, Florian Weimer wrote:
> Currently, the GNU/Linux ABI does not really specify whether the thread
> pointer (the address of the TCB) may change at a function boundary.
[...]
> One important piece of software for GNU is QEMU (not just for GNU/Linux,
> Hurd development also benefits from virtualization).  QEMU uses stackful
> coroutines extensively.  There are some hard-to-change code areas where
> resumption happens across threads unfortunately.  These increasingly
> cause problems with more inlining, inter-procedural analysis, and a
> general push towards LTO (which is also needed for some security
> hardening features).

Thanks a lot for your mail, Florian!

As a context for those who read about this for the very first time: We're 
currently facing the problem that the coroutines in QEMU fail when compiling 
QEMU with -flto on a non-x86 architecture, see:

  https://bugzilla.redhat.com/show_bug.cgi?id=1952483#c6

> Should the GNU toolchain offer something to help out the QEMU
> developers?

I guess that would be extremely helpful...

  Thomas


  parent reply	other threads:[~2021-07-21  7:22 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-20 14:52 Florian Weimer
2021-07-20 15:31 ` Iain Sandoe
2021-07-21  7:22 ` Thomas Huth [this message]
2021-07-22 12:12 ` Richard Biener
2021-07-22 16:01   ` Michael Matz

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