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From:   Marco Elver <elver@google.com>
Date:   Tue, 5 Nov 2019 12:10:56 +0100
Message-ID: <CANpmjNPpVCRhgVgfaApZJCnMKHsGxVUno+o-Fe+7OYKmPvCboQ@mail.gmail.com>
Subject: Re: [PATCH v3 0/9] Add Kernel Concurrency Sanitizer (KCSAN)
To:     "Paul E. McKenney" <paulmck@kernel.org>
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>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
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On Mon, 4 Nov 2019 at 20:47, Paul E. McKenney <paulmck@kernel.org> wrote:
>
> On Mon, Nov 04, 2019 at 07:41:30PM +0100, Marco Elver wrote:
> > On Mon, 4 Nov 2019 at 17:47, Paul E. McKenney <paulmck@kernel.org> wrote:
> > >
> > > On Mon, Nov 04, 2019 at 03:27:36PM +0100, Marco Elver wrote:
> > > > This is the patch-series for the Kernel Concurrency Sanitizer (KCSAN).
> > > > KCSAN is a sampling watchpoint-based data-race detector. More details
> > > > are included in Documentation/dev-tools/kcsan.rst. This patch-series
> > > > only enables KCSAN for x86, but we expect adding support for other
> > > > architectures is relatively straightforward (we are aware of
> > > > experimental ARM64 and POWER support).
> > > >
> > > > To gather early feedback, we announced KCSAN back in September, and
> > > > have integrated the feedback where possible:
> > > > http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@mail.gmail.com
> > > >
> > > > We want to point out and acknowledge the work surrounding the LKMM,
> > > > including several articles that motivate why data-races are dangerous
> > > > [1, 2], justifying a data-race detector such as KCSAN.
> > > > [1] https://lwn.net/Articles/793253/
> > > > [2] https://lwn.net/Articles/799218/
> > > >
> > > > The current list of known upstream fixes for data-races found by KCSAN
> > > > can be found here:
> > > > https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan
> > >
> > > Making this more accessible to more people seems like a good thing.
> > > So, for the series:
> > >
> > > Acked-by: Paul E. McKenney <paulmck@kernel.org>
> >
> > Much appreciated. Thanks, Paul!
> >
> > Any suggestions which tree this could eventually land in?
>
> I would guess that Dmitry might have some suggestions.

I checked and we're both unclear what the most obvious tree to land in
is (the other sanitizers are mm related, which KCSAN is not).

One suggestion that comes to my mind is for KCSAN to go through the
same tree (rcu?) as the LKMM due to their inherent relationship. Would
that make most sense?

Thanks,
-- Marco

> >
> > > > Changelog
> > > > ---------
> > > > v3:
> > > > * Major changes:
> > > >  - Add microbenchmark.
> > > >  - Add instruction watchpoint skip randomization.
> > > >  - Refactor API and core runtime fast-path and slow-path. Compared to
> > > >    the previous version, with a default config and benchmarked using the
> > > >    added microbenchmark, this version is 3.8x faster.
> > > >  - Make __tsan_unaligned __alias of generic accesses.
> > > >  - Rename kcsan_{begin,end}_atomic ->
> > > >    kcsan_{nestable,flat}_atomic_{begin,end}
> > > >  - For filter list in debugfs.c use kmalloc+krealloc instead of
> > > >    kvmalloc.
> > > >  - Split Documentation into separate patch.
> > > >
> > > > v2: http://lkml.kernel.org/r/20191017141305.146193-1-elver@google.com
> > > > * Major changes:
> > > >  - Replace kcsan_check_access(.., {true, false}) with
> > > >    kcsan_check_{read,write}.
> > > >  - Change atomic-instrumented.h to use __atomic_check_{read,write}.
> > > >  - Use common struct kcsan_ctx in task_struct and for per-CPU interrupt
> > > >    contexts.
> > > >
> > > > v1: http://lkml.kernel.org/r/20191016083959.186860-1-elver@google.com
> > > >
> > > > Marco Elver (9):
> > > >   kcsan: Add Kernel Concurrency Sanitizer infrastructure
> > > >   kcsan: Add Documentation entry in dev-tools
> > > >   objtool, kcsan: Add KCSAN runtime functions to whitelist
> > > >   build, kcsan: Add KCSAN build exceptions
> > > >   seqlock, kcsan: Add annotations for KCSAN
> > > >   seqlock: Require WRITE_ONCE surrounding raw_seqcount_barrier
> > > >   asm-generic, kcsan: Add KCSAN instrumentation for bitops
> > > >   locking/atomics, kcsan: Add KCSAN instrumentation
> > > >   x86, kcsan: Enable KCSAN for x86
> > > >
> > > >  Documentation/dev-tools/index.rst         |   1 +
> > > >  Documentation/dev-tools/kcsan.rst         | 217 +++++++++
> > > >  MAINTAINERS                               |  11 +
> > > >  Makefile                                  |   3 +-
> > > >  arch/x86/Kconfig                          |   1 +
> > > >  arch/x86/boot/Makefile                    |   2 +
> > > >  arch/x86/boot/compressed/Makefile         |   2 +
> > > >  arch/x86/entry/vdso/Makefile              |   3 +
> > > >  arch/x86/include/asm/bitops.h             |   6 +-
> > > >  arch/x86/kernel/Makefile                  |   7 +
> > > >  arch/x86/kernel/cpu/Makefile              |   3 +
> > > >  arch/x86/lib/Makefile                     |   4 +
> > > >  arch/x86/mm/Makefile                      |   3 +
> > > >  arch/x86/purgatory/Makefile               |   2 +
> > > >  arch/x86/realmode/Makefile                |   3 +
> > > >  arch/x86/realmode/rm/Makefile             |   3 +
> > > >  drivers/firmware/efi/libstub/Makefile     |   2 +
> > > >  include/asm-generic/atomic-instrumented.h | 393 +++++++--------
> > > >  include/asm-generic/bitops-instrumented.h |  18 +
> > > >  include/linux/compiler-clang.h            |   9 +
> > > >  include/linux/compiler-gcc.h              |   7 +
> > > >  include/linux/compiler.h                  |  35 +-
> > > >  include/linux/kcsan-checks.h              |  97 ++++
> > > >  include/linux/kcsan.h                     | 115 +++++
> > > >  include/linux/sched.h                     |   4 +
> > > >  include/linux/seqlock.h                   |  51 +-
> > > >  init/init_task.c                          |   8 +
> > > >  init/main.c                               |   2 +
> > > >  kernel/Makefile                           |   6 +
> > > >  kernel/kcsan/Makefile                     |  11 +
> > > >  kernel/kcsan/atomic.h                     |  27 ++
> > > >  kernel/kcsan/core.c                       | 560 ++++++++++++++++++++++
> > > >  kernel/kcsan/debugfs.c                    | 275 +++++++++++
> > > >  kernel/kcsan/encoding.h                   |  94 ++++
> > > >  kernel/kcsan/kcsan.h                      | 131 +++++
> > > >  kernel/kcsan/report.c                     | 306 ++++++++++++
> > > >  kernel/kcsan/test.c                       | 121 +++++
> > > >  kernel/sched/Makefile                     |   6 +
> > > >  lib/Kconfig.debug                         |   2 +
> > > >  lib/Kconfig.kcsan                         | 119 +++++
> > > >  lib/Makefile                              |   3 +
> > > >  mm/Makefile                               |   8 +
> > > >  scripts/Makefile.kcsan                    |   6 +
> > > >  scripts/Makefile.lib                      |  10 +
> > > >  scripts/atomic/gen-atomic-instrumented.sh |  17 +-
> > > >  tools/objtool/check.c                     |  18 +
> > > >  46 files changed, 2526 insertions(+), 206 deletions(-)
> > > >  create mode 100644 Documentation/dev-tools/kcsan.rst
> > > >  create mode 100644 include/linux/kcsan-checks.h
> > > >  create mode 100644 include/linux/kcsan.h
> > > >  create mode 100644 kernel/kcsan/Makefile
> > > >  create mode 100644 kernel/kcsan/atomic.h
> > > >  create mode 100644 kernel/kcsan/core.c
> > > >  create mode 100644 kernel/kcsan/debugfs.c
> > > >  create mode 100644 kernel/kcsan/encoding.h
> > > >  create mode 100644 kernel/kcsan/kcsan.h
> > > >  create mode 100644 kernel/kcsan/report.c
> > > >  create mode 100644 kernel/kcsan/test.c
> > > >  create mode 100644 lib/Kconfig.kcsan
> > > >  create mode 100644 scripts/Makefile.kcsan
> > > >
> > > > --
> > > > 2.24.0.rc1.363.gb1bccd3e3d-goog
> > > >
> > >
> > > --
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