From: Eli Cooper <elicooper@gmx.com>
To: Richard Weinberger <richard@nod.at>,
user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Subject: Re: [uml-devel] [PATCH] um: fix FPU register double-restore after sigreturn
Date: Sat, 19 Mar 2016 00:13:47 +0800 [thread overview]
Message-ID: <56EC293B.8020407@gmx.com> (raw)
In-Reply-To: <56EBBA61.4090405@nod.at>
Hi Richard,
On 2016/3/18 16:20, Richard Weinberger wrote:
> I wonder how other architectures handle this case?
> Ideally I'd like to avoid as much extra code as possible in userspace().
Please forgive my ignorance of other architectures. But to the best of
my knowledge, FPU state is not saved and restored around a system call
in x86.
I agree that we should keep userspace() minimal. So what in the first
place is the FPU state save/restore code for? Or, what (except for
sigreturn) could possibly mess the FPU state of the ptrace'd process
without it?
I tried commenting out the FPU restore code in userspace() and tested
with a bunch of kernel modules and userland programs. Nothing bad
happened so far as I can tell.
Thanks,
Eli
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next prev parent reply other threads:[~2016-03-18 16:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-16 1:25 [uml-devel] [PATCH] um: fix FPU register double-restore after sigreturn Eli Cooper
2016-03-17 22:21 ` Richard Weinberger
2016-03-18 1:41 ` Eli Cooper
2016-03-18 8:20 ` Richard Weinberger
2016-03-18 16:13 ` Eli Cooper [this message]
2016-03-18 16:42 ` Jeff Dike
2016-03-18 20:12 ` Richard Weinberger
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