linux-kernel - Re: [PATCH v6 2/4] x86/traps: Print address on #GP

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Date:   Wed, 11 Dec 2019 09:22:30 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Jann Horn <jannh@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v6 2/4] x86/traps: Print address on #GP



> On Dec 11, 2019, at 9:06 AM, Borislav Petkov <bp@...en8.de> wrote:
> 
> On Mon, Dec 09, 2019 at 03:31:18PM +0100, Jann Horn wrote:
>>    I have already sent a patch to syzkaller that relaxes their parsing of GPF
>>    messages (https://github.com/google/syzkaller/commit/432c7650) such that
>>    changes like the one in this patch don't break it.
>>    That patch has already made its way into syzbot's syzkaller instances
>>    according to <https://syzkaller.appspot.com/upstream>.
> 
> Ok, cool.
> 
> I still think we should do the oops number marking, though, as it has
> more benefits than just syzkaller scanning for it. The first oops has always
> been of crucial importance so having the number in there:
> 
> [    2.542218] [1] general protection fault while derefing a non-canonical address 0xdfff000000000001: 0000 [#1] PREEMPT SMP
>        ^
> 
> would make eyeballing oopses even easier. Basically the same reason why
> you're doing this enhancement. :)
> 

Could we spare a few extra bytes to make this more readable?  I can never keep track of which number is the oops count, which is the cpu, and which is the error code.  How about:

OOPS 1: general protection blah blah blah (CPU 0)

and put in the next couple lines “#GP(0)”.

> So let me know if you don't have time to do it or you don't care about
> it etc, and I'll have a look. Independent of those patches, of course -
> those look good so far.
> 
> Thx.
> 
> -- 
> Regards/Gruss,
>    Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette