From patchwork Thu Nov 14 18:02:53 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marco Elver X-Patchwork-Id: 11244163 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AE65D13B2 for ; Thu, 14 Nov 2019 18:04:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 72BFE20723 for ; Thu, 14 Nov 2019 18:04:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lr7v9t/b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727152AbfKNSEy (ORCPT ); Thu, 14 Nov 2019 13:04:54 -0500 Received: from mail-wm1-f74.google.com ([209.85.128.74]:55403 "EHLO mail-wm1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726491AbfKNSEA (ORCPT ); Thu, 14 Nov 2019 13:04:00 -0500 Received: by mail-wm1-f74.google.com with SMTP id h191so4388865wme.5 for ; Thu, 14 Nov 2019 10:03:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=1bg0Urry1BGwaxpDX8MHZFNgYP5IGRugkAlFUvPLa/I=; b=lr7v9t/b/nWB+oAlbYHlnG9ii8vIW9kKStfj1dl2F+rlYORyMHGnNhsdqh03G2C0// yZ5xgTbXsNNf3QwN0Qwga6q5nM/rxjeVaZ9U0zczdCT+0e79wzZS/U9XMus96cOP/QX/ k+CVWVti+mZkubWF9QrVTJw5SEehpsKf4hZ7DQ09LIv3oofslpgizYbK8l6+ycIKA89x lJJ9GsqBG24Ur5vUOlwu59yaqPO0FZzn4qgShqmaoVE0Mt8y0BC4GS/WhwSSgu2zcAJI XG0iaZB3EWiAvVB2PFnjG7HFSd/bTbpARaMvFNvmSCEtNF2A9luiODjbY2pxefIlmYv8 L4nQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=1bg0Urry1BGwaxpDX8MHZFNgYP5IGRugkAlFUvPLa/I=; b=qSFw1GBh3iqnyn+FFLd4zQ5hj+Mm3n06Kz8EiwaONFCbnAOpkWEm6xeHw8vVevRixf AbzsAdhHJ+FX2rDYlDp4nWpf7qA2b6TtotUo/UA3j0pCMoLj3fKLbZlL4K0FSKNJJm3O 4R0EO5hUkvG94D2d+johvVpI/HE4JbBnPsWoUwkjs4SVs1FztPwJcOu7ChMV+SSXLMLs WTe5uLgqDTsBNQcVqXSAamVMQ0PY+Eock3b705IiCP2I1tYE7lFOx/OF/d8S1eucmpwN aF2Z0/5aMmv+BZK5h0Fw5f0mh4pjd0K22fDjiQcOz+M6J7PqvOyrf850viZDINF8M4yG PSaw== X-Gm-Message-State: APjAAAXcWLJeLz++I1T7ADpvi0GWqQOOl5z28rChRrcIYP9IWpPpT8Bo tIhHFabdZf3Ve9VIN+thk2ic1aX9kA== X-Google-Smtp-Source: APXvYqyCRLhzabKP15Hc3I8tuyq3pOVGFzSfCNQc1mA04B8Z4nfTDX8KQ8VJZaVdt16PEvULqCx0tNT5ug== X-Received: by 2002:a5d:4585:: with SMTP id p5mr9720266wrq.134.1573754637105; Thu, 14 Nov 2019 10:03:57 -0800 (PST) Date: Thu, 14 Nov 2019 19:02:53 +0100 Message-Id: <20191114180303.66955-1-elver@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.24.0.rc1.363.gb1bccd3e3d-goog Subject: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) From: Marco Elver To: 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 Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org 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 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