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From: Marco Elver <elver@google.com>
To: Qian Cai <cai@lca.pw>
Cc: LKMM Maintainers -- Akira Yokosawa <akiyks@gmail.com>,
	Alan Stern <stern@rowland.harvard.edu>,
	Alexander Potapenko <glider@google.com>,
	Andrea Parri <parri.andrea@gmail.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Andy Lutomirski <luto@kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>, Boqun Feng <boqun.feng@gmail.com>,
	Borislav Petkov <bp@alien8.de>, Daniel Axtens <dja@axtens.net>,
	Daniel Lustig <dlustig@nvidia.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	David Howells <dhowells@redhat.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Jade Alglave <j.alglave@ucl.ac.uk>,
	Joel Fernandes <joel@joelfernandes.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Luc Maranget <luc.maranget@inria.fr>,
	Mark Rutland <mark.rutland@arm.com>,
	Nicholas Piggin <npiggin@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Will Deacon <will@kernel.org>, Eric Dumazet <edumazet@google.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	linux-efi@vger.kernel.org,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	"the arch/x86 maintainers" <x86@kernel.org>
Subject: Re: [PATCH v4 01/10] kcsan: Add Kernel Concurrency Sanitizer infrastructure
Date: Tue, 19 Nov 2019 20:54:14 +0100	[thread overview]
Message-ID: <CANpmjNPiKg++=QHUjD87dqiBU1pHHfZmGLAh1gOZ+4JKAQ4SAQ@mail.gmail.com> (raw)
In-Reply-To: <1574191653.9585.6.camel@lca.pw>

On Tue, 19 Nov 2019 at 20:27, Qian Cai <cai@lca.pw> wrote:
>
> On Thu, 2019-11-14 at 19:02 +0100, 'Marco Elver' via kasan-dev wrote:
>
> > +menuconfig KCSAN
> > +     bool "KCSAN: watchpoint-based dynamic data race detector"
> > +     depends on HAVE_ARCH_KCSAN && !KASAN && STACKTRACE
>
> "!KASAN" makes me sorrow. What's problem of those two?

Both of them instrument memory accesses, and gcc doesn't let us
combine '-fsanitize={kernel-,}address' and '-fsanitize=thread'.

> cc1: error: ‘-fsanitize=address’ and ‘-fsanitize=kernel-address’ are incompatible with ‘-fsanitize=thread’

In principle, it may be possible:
- either by updating the compiler, which we want to avoid because we'd
have to convince gcc and clang to do this; I can see this being
infeasible because the compiler needs to become aware (somehow
propagate in the IR) of what is ASAN inline-instrumentation and what
is TSAN instrumentation and not emit recursive instrumentation.
- or somehow merging the instrumentation, but, IMHO this is probably a
really bad idea for various other reasons (complexity, performance,
stability, etc.).

Regardless of approach, my guess is that the complexity outweighs any
benefits this may provide in the end. Not only would a hypothetical
kernel that combines these be extremely slow, it'd also diminish the
practical value because testing and finding bugs would also be
impaired due to performance.

Thanks,
-- Marco

  reply	other threads:[~2019-11-19 19:54 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-14 18:02 [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) Marco Elver
2019-11-14 18:02 ` [PATCH v4 01/10] kcsan: Add Kernel Concurrency Sanitizer infrastructure Marco Elver
2019-11-19 19:27   ` Qian Cai
2019-11-19 19:54     ` Marco Elver [this message]
2019-11-19 21:42       ` Qian Cai
2019-11-19 21:53         ` Marco Elver
2020-01-03  5:13   ` Qian Cai
2020-01-06 12:46     ` Marco Elver
2020-01-14 11:08       ` Qian Cai
2020-01-14 12:51         ` Marco Elver
2020-01-14 19:22         ` Paul E. McKenney
2020-01-14 20:30           ` Qian Cai
2020-01-14 21:34             ` Paul E. McKenney
2020-01-14 21:48               ` Qian Cai
2020-01-14 22:09                 ` Paul E. McKenney
2019-11-14 18:02 ` [PATCH v4 02/10] include/linux/compiler.h: Introduce data_race(expr) macro Marco Elver
2019-11-14 18:02 ` [PATCH v4 03/10] kcsan: Add Documentation entry in dev-tools Marco Elver
2019-11-14 18:02 ` [PATCH v4 04/10] objtool, kcsan: Add KCSAN runtime functions to whitelist Marco Elver
2019-11-14 18:02 ` [PATCH v4 05/10] build, kcsan: Add KCSAN build exceptions Marco Elver
2019-11-14 18:02 ` [PATCH v4 06/10] seqlock, kcsan: Add annotations for KCSAN Marco Elver
2019-11-14 18:03 ` [PATCH v4 07/10] seqlock: Require WRITE_ONCE surrounding raw_seqcount_barrier Marco Elver
2019-11-14 18:03 ` [PATCH v4 08/10] asm-generic, kcsan: Add KCSAN instrumentation for bitops Marco Elver
2019-11-15 11:55   ` Marco Elver
2019-11-14 18:03 ` [PATCH v4 09/10] locking/atomics, kcsan: Add KCSAN instrumentation Marco Elver
2019-11-14 18:03 ` [PATCH v4 10/10] x86, kcsan: Enable KCSAN for x86 Marco Elver
2019-11-14 19:50 ` [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) Paul E. McKenney
2019-11-14 21:33   ` Marco Elver
2019-11-14 22:15     ` Paul E. McKenney
2019-11-15 12:02       ` Marco Elver
2019-11-15 16:41         ` Paul E. McKenney
2019-11-15 17:14           ` Marco Elver
2019-11-15 20:43             ` Paul E. McKenney
2019-11-16  8:20               ` Marco Elver
2019-11-16 15:34                 ` Paul E. McKenney
2019-11-16 18:09                   ` Marco Elver
2019-11-16 18:28                     ` Paul E. McKenney
2019-11-19 19:50 ` Qian Cai
2019-11-19 20:12 ` Qian Cai
2019-11-19 21:50   ` Marco Elver
2019-11-20 15:54     ` Marco Elver

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