linux-kernel - Re: [PATCH] x86/fpu: Allow PKRU to be (once again) written by ptrace.

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Date:   Wed, 9 Nov 2022 11:23:02 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] x86/fpu: Allow PKRU to be (once again) written by ptrace.

[Note: this mail is primarily send for documentation purposes and/or for
regzbot, my Linux kernel regression tracking bot. That's why I removed
most or all folks from the list of recipients, but left any that looked
like a mailing lists. These mails usually contain '#forregzbot' in the
subject, to make them easy to spot and filter out.]

[TLDR: I'm adding this regression report to the list of tracked
regressions; all text from me you find below is based on a few templates
paragraphs you might have encountered already already in similar form.]

Hi, this is your Linux kernel regression tracker.

On 31.07.22 07:03, Kyle Huey wrote:
> From: Kyle Huey <me@...ehuey.com>
> 
> When management of the PKRU register was moved away from XSTATE, emulation
> of PKRU's existence in XSTATE was added for APIs that read XSTATE, but not
> for APIs that write XSTATE. This can be seen by running gdb and executing
> `p $pkru`, `set $pkru = 42`, and `p $pkru`. On affected kernels (5.14+) the
> write to the PKRU register (which gdb performs through ptrace) is ignored.

Seem I missed this one, but apparently it needs tracking.

#regzbot ^introduced e84ba47e313dbc
#regzbot title x86/fpu: emulation of PKRU's existence in XSTATE missing
for APIs that write XSTATE
#regzbot ignore-activity
#regzbot monitor
https://lore.kernel.org/all/20221107063807.81774-1-khuey@kylehuey.com/

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

P.S.: As the Linux kernel's regression tracker I deal with a lot of
reports and sometimes miss something important when writing mails like
this. If that's the case here, don't hesitate to tell me in a public
reply, it's in everyone's interest to set the public record straight.