From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 828CCC432C0 for ; Tue, 19 Nov 2019 19:51:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4C98022444 for ; Tue, 19 Nov 2019 19:51:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="T1mhHDOS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727007AbfKSTvG (ORCPT ); Tue, 19 Nov 2019 14:51:06 -0500 Received: from mail-qv1-f68.google.com ([209.85.219.68]:42051 "EHLO mail-qv1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726911AbfKSTvF (ORCPT ); Tue, 19 Nov 2019 14:51:05 -0500 Received: by mail-qv1-f68.google.com with SMTP id n4so5561832qvq.9 for ; Tue, 19 Nov 2019 11:51:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=SJkWiQS++k8drSI02mEHrqK7VAxEXqYSD3skFTgLnIk=; b=T1mhHDOSwFNvLSuuNxU346Rj4/TLbq4zqYQ4+phQee3AIsZik1mcHS4CpNzjfT1ENb M6Ro/jOUSTAeFYDEnMTN7jjNdbw+t5A3decKe5XgrR1ohw+3IUYa65Z4i/ePOjuYSH82 aqhiOdx+eamWIdAf82f0cPmBCpPSZ4RUAW0VmKA9o9Ek74fe5sqE9gbPpIQU+o3MBpga B7pwywhkknVBDG36KdnzdcViFgg+c/9qvfRhutnGOp5a3SFyycJzRbFSf4Pz/qVp9rXO zrqaWM+NvsVMWya3d2XT+PwtocfxNCLKMikOCY9ziUSO6iTdPEiAPeZKEN6VI2nGpodm d7Qw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=SJkWiQS++k8drSI02mEHrqK7VAxEXqYSD3skFTgLnIk=; b=VcUQXuyG74P0GJUU4axIn7fzuYxY44972FFRdvfSeQkHevFQ24UJplu9XiETQk3cKO ktjlAeGZTuyYq9156o27gMZCw7hO/F8ahta1eJrbd7MWDG1fKtVR/eG1hYw2+U21cSQA yv+poQo1qPHv8lHreb3Mg0ERSI+/OR4mGYdpNp5MNMrwDqKm7QcktuETYipsTHfAUsu/ HPJCvrqzygNl3SzuObzYh3e5ms6SEzjhqHH+MVxUU9EjGYg9xvBqVwVUqrBo6tIXQ/TQ WJq7vZyadkteOXRbniYryQrEq4IjxD+E9pRL86zPsOhDAhUD/FBcMoE5RsJhrxv1loPg 3NdQ== X-Gm-Message-State: APjAAAV2RABDe8bQFPCBlU+e+Yh+uyPI8iwtSGoCg9nQbnZpvUyrUvT/ CfmWAfslc+f66y44J1U/lboS7w== X-Google-Smtp-Source: APXvYqxxCAqo9RtGklNIbMoBFOzXnASLPiWGTquecJBf0e0W3gSp/u07oE4/fHgEJ0Rg0S68bdLdqA== X-Received: by 2002:a0c:e847:: with SMTP id l7mr279965qvo.14.1574193064216; Tue, 19 Nov 2019 11:51:04 -0800 (PST) Received: from dhcp-41-57.bos.redhat.com (nat-pool-bos-t.redhat.com. [66.187.233.206]) by smtp.gmail.com with ESMTPSA id y24sm10542040qki.104.2019.11.19.11.51.00 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 Nov 2019 11:51:03 -0800 (PST) Message-ID: <1574193059.9585.8.camel@lca.pw> Subject: Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN) From: Qian Cai To: Marco Elver 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 Date: Tue, 19 Nov 2019 14:50:59 -0500 In-Reply-To: <20191114180303.66955-1-elver@google.com> References: <20191114180303.66955-1-elver@google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-efi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org 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). Just booting x86 systems because kcsan_setup_watchpoint() disabled hard irqs? [    8.926145][    T0] ------------[ cut here ]------------ [    8.927850][    T0] DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled) [    80] WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:4406 check_flags.part.26+0x102/0x240 [    8.933072][    T0] Modules linked in: [    8.933072][    T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-rc8-next- 20191119+ #2 [    8.933072][    T0] Hardware name: HP ProLiant XL420 Gen9/ProLiant XL420 Gen9, BIOS U19 12/27/2015 [    8.933072][    T0] RIP: 0010:check_flags.part.26+0x102/0x240 [    8.933072][    T0] Code: 7b a2 e8 51 6d 15 00 44 8b 05 fa df 45 01 45 85 c0 0f 85 27 76 00 00 48 c7 c6 02 d6 3b a2 48 c7 c7 79 36 3b a2 e8 2f 9f f5 ff <0f> e9 0d 76 00 00 65 48 8b 3c 25 40 3f 01 00 e8 89 f0 ff ff e8 [    8.933072][    T0] RSP: 0000:ffffffffa2603860 EFLAGS: 00010086 [    8.933072][    T0] RAX: 0000000000000000 RBX: ffffffffa2617b40 RCX: 0000000000000000 [    8.933072][    T0] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 [    8.933072][    T0] RBP: ffffffffa2603868 R08: 0000000000000000 R09: 0000ffffa27bcad4 [    8.933072][    T0] R10: 0000ffffffffffff R11: 0000ffffa27bcad7 R12: 0000000000000168 [    8.933072][    T0] R13: 0000000000092cc0 R14: 0000000000000246 R15: ffffffffa1664c89 [    8.933072][    T0] FS:  0000000000000000(0000) GS:ffff8987f3000000(0000) knlGS:0000000000000000 [    8.933072][    T0] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [    8.933072][    T0] CR2: ffff898bfc9ff000 CR3: 000000033dc0e001 CR4: 00000000001606f0 [    8.933072][    T0] Call Trace: [    8.933072][    T0]  lock_is_held_type+0x66/0x13072][    T0]  ? rcu_is_watching+0x79/0xa0 [    8.933072][    T0]  ? create_object+0x69/0x690 [    8.933072][    T0]  rcu_read_lock_sched_held+0x7f/0xa0 [    8.933072][    T0]  kmem_cache_alloc+0x3b2/0x420 [    8.933072][    T0]  ? create_object+0x69/0x690 [    8.933072][    T0]  create_object+0x69/0x690 [    8.933072][    T0]  ? find_next_bit+0x7b/0xa0 [    8.933072][    T0]  kmemleak_alloc_percpu+0xde/0x170 [    8.933072][    T0]  pcpu_alloc+0x683/0xc90 [    8.933072][    T0]  __alloc_percpu+0x2d/0x40 [    8.933072][    T0]  alloc_vfsmnt+0xd1/0x380 [    8.933072][    T0]  vfs_create_mount+0x7f/0x2e0 [    8.933072][    T0]  ? proc_get_tree+0x4d/0x60 [    8.933072][    T0]  fc_mount+0x6d/0x80 [    8.933072][    T0]  pid_ns_prepare_proc+0x133/0x190 [    8.933072][    T0]  alloc_pid+0x5c3/0x600 [    8.933072][    T0]  copy_process+0x1ca3/0x3480 [    8.933072][    T0]  ? __lock_acquire+0x739/0x25d0 [    8.933072][    T0]  _do_fork+0xaa/0x9c0 [    8.933072][    T0]  ? rcu_blocking_is_gp+0x83/0xb0 [    8.933072][    T0]  ? synchronize_rcu_expedited+0x80/0x6c0 [    8.933072][    T0]  ? rcu_blocking_is_gp+0x83/0xb0 [    8.933072][    T0]  ? rest_init+0x381/0x381 [    8.933072][    T0]  kernel_thread+0xb0/0xe0 [    8.933072][    T0]  ? rest_init+0x381/0x381 [    8.933072][    T0]  rest_init+0x31/0x381 [    8.933072][   st_init+0x17/0x29 [    8.933072][    T0]  start_kernel+0x6ac/0x6d0 [    8.933072][    T0]  x86_64_start_reservations+0x24/0x26 [    8.933072][    T0]  x86_64_start_kernel+0xef/0xf6 [    8.933072][    T0]  secondary_startup_64+0xb6/0xc0 [    8.933072][    T0] irq event stamp: 75594 [    8.933072][    T0] hardirqs last  enabled at (75593): [] trace_hardirqs_on_thunk+0x1a/0x1c [    8.933072][    T0] hardirqs last disabled at (75594): [] kcsan_setup_watchpoint+0x96/0x200 [    8.933072][    T0] softirqs last  enabled at (75592): [] __do_softirq+0x34c/0x57c [    8.933072][    T0] softirqs last disabled at (75585): [] irq_exit+0xa2/0xc0 [    8.933072][    T0] ---[ end trace f4a667495da45c20 ]--- [    8.933072][    T0] possible reason: unannotated irqs-on. [    8.933072][    T0] irq event stamp: 75594 [    8.933072][    T0] hardirqs last  enabled at (75593): [] trace_hardirqs_on_thunk+0x1a/0x1c [    8.933072][    T0] hardirqs last disabled at (75594): [] kcsan_setup_watchpoint+0x96/0x200 [    8.933072][    T0] softirqs last  enabled at (75592): [] __do_softirq+0x34c/0x57c [    8.933072][    T0] softirqs last disabled at (75585): [] irq_exit+0xa2/0xc0 > > 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 >