linux-kernel - Re: [GIT PULL] x86 fixes

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Message-ID: <CAHk-=whYb2L_atsRk9pBiFiVLGe5wNZLHhRinA69yu6FiKvDsw@mail.gmail.com>
Date: Sat, 15 Jun 2024 11:36:33 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	Peter Zijlstra <peterz@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [GIT PULL] x86 fixes

On Sat, 15 Jun 2024 at 01:13, Ingo Molnar <mingo@...nel.org> wrote:
>
>  - Fix the 8 bytes get_user() logic on x86-32

This is clearly a fix, but I think it's a bit ugly.

Instead of adding _more_ special cases for size 8, we could just remove them.

Making the 8-bit two-word versions just clear %ecx before doing the
first load means that all the exception handling becomes entirely
unified.

And then you can just use a nice macro for all the user accesses, and
the #ifdefs go away entirely for all exception handling. All that
remains is the "do I do a 'movq' or an xor and two movl's" question.

Something ENTIRELY UNTESTED like this, IOW.

I did check that it seemed to generate sane code on both 32-bit and
64-bit, but no _actual_ testing.

               Linus

View attachment "patch.diff" of type "text/x-patch" (3617 bytes)