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From:   Andy Lutomirski <luto@amacapital.net>
Mime-Version: 1.0 (1.0)
Subject: Re: [PATCH v6 2/4] x86/traps: Print address on #GP
Date:   Wed, 11 Dec 2019 09:22:30 -0800
Message-Id: <BC48F4AD-8330-4ED6-8BE8-254C835506A5@amacapital.net>
References: <20191211170632.GD14821@zn.tnic>
Cc:     Jann Horn <jannh@google.com>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>, kasan-dev@googlegroups.com,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>
In-Reply-To: <20191211170632.GD14821@zn.tnic>
To:     Borislav Petkov <bp@alien8.de>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Dec 11, 2019, at 9:06 AM, Borislav Petkov <bp@alien8.de> wrote:
>=20
> =EF=BB=BFOn 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 th=
at
>>    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>.
>=20
> Ok, cool.
>=20
> 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 alwa=
ys
> been of crucial importance so having the number in there:
>=20
> [    2.542218] [1] general protection fault while derefing a non-canonical=
 address 0xdfff000000000001: 0000 [#1] PREEMPT SMP
>        ^
>=20
> would make eyeballing oopses even easier. Basically the same reason why
> you're doing this enhancement. :)
>=20

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

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

and put in the next couple lines =E2=80=9C#GP(0)=E2=80=9D.

> 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.
>=20
> Thx.
>=20
> --=20
> Regards/Gruss,
>    Boris.
>=20
> https://people.kernel.org/tglx/notes-about-netiquette