From: Mark Rutland <mark.rutland@arm.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Popov <alex.popov@linux.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Quentin Casasnovas <quentin.casasnovas@oracle.com>,
andreyknvl <andreyknvl@google.com>,
Kees Cook <keescook@chromium.org>,
Vegard Nossum <vegard.nossum@oracle.com>,
syzkaller <syzkaller@googlegroups.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/3] kcov: support comparison operands collection
Date: Tue, 10 Oct 2017 10:56:19 +0100 [thread overview]
Message-ID: <20171010095618.GF27659@leverpostej> (raw)
In-Reply-To: <CACT4Y+apUD89-neN7GUsbdZ9a1hMgRPQk-h4dhC9iDf+_6Kh=w@mail.gmail.com>
On Mon, Oct 09, 2017 at 08:46:18PM +0200, 'Dmitry Vyukov' via syzkaller wrote:
> On Mon, Oct 9, 2017 at 8:37 PM, Mark Rutland <mark.rutland@arm.com> wrote:
> > On Mon, Oct 09, 2017 at 08:15:10PM +0200, 'Dmitry Vyukov' via syzkaller wrote:
> >> On Mon, Oct 9, 2017 at 5:46 PM, Mark Rutland <mark.rutland@arm.com> wrote:
> >> > On Mon, Oct 09, 2017 at 05:05:19PM +0200, Alexander Potapenko wrote:
> >
> >> > ... I note that a few places in the kernel use a 128-bit type. Are
> >> > 128-bit comparisons not instrumented?
> >>
> >> Yes, they are not instrumented.
> >> How many are there? Can you give some examples?
> >
> > From a quick scan, it doesn't looks like there are currently any
> > comparisons.
> >
> > It's used as a data type in a few places under arm64:
> >
> > arch/arm64/include/asm/checksum.h: __uint128_t tmp;
> > arch/arm64/include/asm/checksum.h: tmp = *(const __uint128_t *)iph;
> > arch/arm64/include/asm/fpsimd.h: __uint128_t vregs[32];
> > arch/arm64/include/uapi/asm/ptrace.h: __uint128_t vregs[32];
> > arch/arm64/include/uapi/asm/sigcontext.h: __uint128_t vregs[32];
> > arch/arm64/kernel/signal32.c: __uint128_t raw;
> > arch/arm64/kvm/guest.c: __uint128_t tmp;
>
> Then I think we just continue ignoring them for now :)
> In the future we can extend kcov to trace 128-bits values. We will
> need to add a special flag and write 2 consecutive entries for them.
> Or something along these lines.
Just wanted to make sure that we weren't backing ourselves into a corner
w.r.t. ABI; that sounds fine to me.
Thanks,
Mark.
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next prev parent reply other threads:[~2017-10-10 9:57 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-09 15:05 [PATCH v2 1/3] kcov: support comparison operands collection Alexander Potapenko
2017-10-09 15:05 ` [PATCH v2 2/3] Makefile: support flag -fsanitizer-coverage=trace-cmp Alexander Potapenko
2017-10-09 15:53 ` Andrey Ryabinin
2017-10-10 15:28 ` Alexander Potapenko
2017-10-10 21:53 ` kbuild test robot
2017-10-09 15:05 ` [PATCH v2 3/3] kcov: update documentation Alexander Potapenko
2017-10-09 15:46 ` [PATCH v2 1/3] kcov: support comparison operands collection Mark Rutland
2017-10-09 18:15 ` Dmitry Vyukov
2017-10-09 18:37 ` Mark Rutland
2017-10-09 18:46 ` Dmitry Vyukov
2017-10-10 9:56 ` Mark Rutland [this message]
2017-10-10 15:28 ` Alexander Potapenko
2017-10-10 15:34 ` Dmitry Vyukov
2017-10-11 9:56 ` Alexander Potapenko
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