linux-kernel - Re: [PATCH 1/1] x86/fpu: Allow clearcpuid= to clear several bits

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20200423014137.GM608746@tassilo.jf.intel.com>
Date:   Wed, 22 Apr 2020 18:41:37 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     John Haxby <john.haxby@...cle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Jonathan Corbet <corbet@....net>,
        x86@...nel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/1] x86/fpu: Allow clearcpuid= to clear several bits

> 
> I did wonder about that.   However, cmdline_find_option() is specifically documented as 
> 
>  * Find a non-boolean option (i.e. option=argument). In accordance with
>  * standard Linux practice, if this option is repeated, this returns the
>  * last instance on the command line.

Okay so would need a special version that uses the first and an option
to pass the cmdline string.

> 
> And since that appeared in 2017 I decided to stick with the new-fangled interface :)   This is a little-used feature; I'm not sure it's worth the effort of parsing the command line for the old style.  What do you think?

I'm not sure it's that little used.  We use it quite a bit for testing
and workarounds, and it might be that some of those are deployed.

-Andi