From: Qian Cai <cai@lca.pw>
To: Marco Elver <elver@google.com>
Cc: akiyks@gmail.com, stern@rowland.harvard.edu, glider@google.com,
parri.andrea@gmail.com, andreyknvl@google.com, luto@kernel.org,
ard.biesheuvel@linaro.org, arnd@arndb.de, boqun.feng@gmail.com,
bp@alien8.de, dja@axtens.net, dlustig@nvidia.com,
dave.hansen@linux.intel.com, dhowells@redhat.com,
dvyukov@google.com, hpa@zytor.com, mingo@redhat.com,
j.alglave@ucl.ac.uk, joel@joelfernandes.org, corbet@lwn.net,
jpoimboe@redhat.com, luc.maranget@inria.fr, mark.rutland@arm.com,
npiggin@gmail.com, paulmck@kernel.org, peterz@infradead.org,
tglx@linutronix.de, will@kernel.org, edumazet@google.com,
kasan-dev@googlegroups.com, linux-arch@vger.kernel.org,
linux-doc@vger.kernel.org, linux-efi@vger.kernel.org,
linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, x86@kernel.org
Subject: Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN)
Date: Tue, 19 Nov 2019 15:12:59 -0500 [thread overview]
Message-ID: <1574194379.9585.10.camel@lca.pw> (raw)
In-Reply-To: <20191114180303.66955-1-elver@google.com>
On Thu, 2019-11-14 at 19:02 +0100, 'Marco Elver' via kasan-dev 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).
This does not allow the system to boot. Just hang forever at the end.
https://cailca.github.io/files/dmesg.txt
the config (dselect KASAN and select KCSAN with default options):
https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config
>
> 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
>
> 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
>
> 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/
>
> Race conditions vs. data races
> ------------------------------
>
> Race conditions are logic bugs, where unexpected interleaving of racing
> concurrent operations result in an erroneous state.
>
> Data races on the other hand are defined at the *memory model/language
> level*. Many data races are also harmful race conditions, which a tool
> like KCSAN reports! However, not all data races are race conditions and
> vice-versa. KCSAN's intent is to report data races according to the
> LKMM. A data race detector can only work at the memory model/language
> level.
>
> Deeper analysis, to find high-level race conditions only, requires
> conveying the intended kernel logic to a tool. This requires (1) the
> developer writing a specification or model of their code, and then (2)
> the tool verifying that the implementation matches. This has been done
> for small bits of code using model checkers and other formal methods,
> but does not scale to the level of what can be covered with a dynamic
> analysis based data race detector such as KCSAN.
>
> For reasons outlined in [1, 2], data races can be much more subtle, but
> can cause no less harm than high-level race conditions.
>
> Changelog
> ---------
> v4:
> * Major changes:
> - Optimizations resulting in performance improvement of 33% (on
> microbenchmark).
> - Deal with nested interrupts for atomic_next.
> - Simplify report.c (removing double-locking as well), in preparation
> for KCSAN_REPORT_VALUE_CHANGE_ONLY.
> - Add patch to introduce "data_race(expr)" macro.
> - Introduce KCSAN_REPORT_VALUE_CHANGE_ONLY option for further filtering of data
> races: if a conflicting write was observed via a watchpoint, only report the
> data race if a value change was observed as well. The option will be enabled
> by default on syzbot. (rcu-functions will be excluded from this filter at
> request of Paul McKenney.) Context:
> http://lkml.kernel.org/r/CANpmjNOepvb6+zJmDePxj21n2rctM4Sp4rJ66x_J-L1UmNK54A@mail.gmail.com
>
> v3: http://lkml.kernel.org/r/20191104142745.14722-1-elver@google.com
> * 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 (10):
> kcsan: Add Kernel Concurrency Sanitizer infrastructure
> include/linux/compiler.h: Introduce data_race(expr) macro
> 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 | 256 +++++++++
> 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 | 4 +
> arch/x86/kernel/cpu/Makefile | 3 +
> arch/x86/lib/Makefile | 4 +
> arch/x86/mm/Makefile | 4 +
> 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 | 57 +-
> 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 | 626 ++++++++++++++++++++++
> kernel/kcsan/debugfs.c | 275 ++++++++++
> kernel/kcsan/encoding.h | 94 ++++
> kernel/kcsan/kcsan.h | 108 ++++
> kernel/kcsan/report.c | 320 +++++++++++
> kernel/kcsan/test.c | 121 +++++
> kernel/sched/Makefile | 6 +
> lib/Kconfig.debug | 2 +
> lib/Kconfig.kcsan | 118 ++++
> 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, 2641 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
>
next prev parent reply other threads:[~2019-11-19 20:13 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
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 [this message]
2019-11-19 21:50 ` Marco Elver
2019-11-20 15:54 ` Marco Elver
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