linux-kernel - Re: [patch V181 49/54] x86/dumpstack: Indicate in Oops whether pti is configured and enabled

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Date:   Wed, 20 Dec 2017 23:03:41 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirsky <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>, keescook@...gle.com,
        hughd@...gle.com, Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>, aliguori@...zon.com,
        Will Deacon <will.deacon@....com>,
        Vlastimil Babka <vbabka@...e.cz>, daniel.gruss@...k.tugraz.at
Subject: Re: [patch V181 49/54] x86/dumpstack: Indicate in Oops whether pti
 is configured and enabled

On Wed, 20 Dec 2017, Thomas Gleixner wrote:

> From: Vlastimil Babka <vbabka@...e.cz>
> 
> CONFIG_PAGE_TABLE_ISOLATION is relatively new and intrusive feature that may
> still have some corner cases which could take some time to manifest and be
> fixed. It would be useful to have Oops messages indicate whether it was
> enabled for building the kernel, and whether it was disabled during boot.
> 
> Example of fully enabled:
> 
> 	Oops: 0001 [#1] SMP PTI
> 
> Example of enabled during build, but disabled during boot:
> 
> 	Oops: 0001 [#1] SMP NOPTI
> 
> We can decide to remove this after the feature has been tested in the field
> long enough.
> 
> [ tglx: Made it use boot_cpu_has() as requested by Borislav ]
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Reviewed-by: Eduardo Valentin <eduval@...zon.com>
> Acked-by: Dave Hansen <dave.hansen@...el.com>

FWIW

	Acked-by: Jiri Kosina <jkosina@...e.cz>

I've had a much more stupid variant of this when fuzzing pti/nopti kernels 
(distro backports, of course), and it was really helpful when diving into 
the crashes.

Thanks,

-- 
Jiri Kosina
SUSE Labs