From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id 12E1A6B0253 for ; Tue, 12 Sep 2017 13:42:21 -0400 (EDT) Received: by mail-io0-f198.google.com with SMTP id q7so15264787ioi.3 for ; Tue, 12 Sep 2017 10:42:21 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id m202sor4549513ita.66.2017.09.12.10.42.19 for (Google Transport Security); Tue, 12 Sep 2017 10:42:20 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <663c2a30de845dd13cf3cf64c3dfd437295d5ce2.1504109849.git.dvyukov@google.com> <20170830182357.GD32493@leverpostej> From: Dmitry Vyukov Date: Tue, 12 Sep 2017 19:41:58 +0200 Message-ID: Subject: Re: [PATCH 1/3] kcov: support comparison operands collection Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Mark Rutland Cc: Andrew Morton , "linux-mm@kvack.org" , Victor Chibotaru , Alexander Popov , Andrey Ryabinin , Kees Cook , Vegard Nossum , Quentin Casasnovas , syzkaller , LKML On Wed, Aug 30, 2017 at 9:08 PM, Dmitry Vyukov wrote: > On Wed, Aug 30, 2017 at 8:23 PM, Mark Rutland wrote: >> Hi, >> >> On Wed, Aug 30, 2017 at 06:23:29PM +0200, Dmitry Vyukov wrote: >>> From: Victor Chibotaru >>> >>> Enables kcov to collect comparison operands from instrumented code. >>> This is done by using Clang's -fsanitize=trace-cmp instrumentation >>> (currently not available for GCC). >> >> What's needed to build the kernel with Clang these days? >> >> I was under the impression that it still wasn't possible to build arm64 >> with clang due to a number of missing features (e.g. the %a assembler >> output template). >> >>> The comparison operands help a lot in fuzz testing. E.g. they are >>> used in Syzkaller to cover the interiors of conditional statements >>> with way less attempts and thus make previously unreachable code >>> reachable. >>> >>> To allow separate collection of coverage and comparison operands two >>> different work modes are implemented. Mode selection is now done via >>> a KCOV_ENABLE ioctl call with corresponding argument value. >>> >>> Signed-off-by: Victor Chibotaru >>> Cc: Andrew Morton >>> Cc: Mark Rutland >>> Cc: Alexander Popov >>> Cc: Andrey Ryabinin >>> Cc: Kees Cook >>> Cc: Vegard Nossum >>> Cc: Quentin Casasnovas >>> Cc: syzkaller@googlegroups.com >>> Cc: linux-mm@kvack.org >>> Cc: linux-kernel@vger.kernel.org >>> --- >>> Clang instrumentation: >>> https://clang.llvm.org/docs/SanitizerCoverage.html#tracing-data-flow >> >> How stable is this? >> >> The comment at the end says "This interface is a subject to change." > > > The intention is that this is not subject to change anymore (since we > are using it in kernel). > I've mailed change to docs: https://reviews.llvm.org/D37303 > > FWIW, there is patch in flight that adds this instrumentation to gcc: > https://groups.google.com/forum/#!topic/syzkaller/CSLynn6nI-A > It seems to be stalled on review phase, though. Good news is that this is submitted to gcc in 251801. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org