From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-13.3 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id C27817DE5B for ; Thu, 17 Oct 2019 14:14:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439876AbfJQOOM (ORCPT ); Thu, 17 Oct 2019 10:14:12 -0400 Received: from mail-wr1-f74.google.com ([209.85.221.74]:42916 "EHLO mail-wr1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2439912AbfJQONj (ORCPT ); Thu, 17 Oct 2019 10:13:39 -0400 Received: by mail-wr1-f74.google.com with SMTP id e25so440698wra.9 for ; Thu, 17 Oct 2019 07:13:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=Or9Dc22i/7f/YW0tvEwykVYSyBSv8lYxv1cGbeL+tYY=; b=voVDOFtDURoWe70EuQZCthSF4tD+2HviE8KiUDoZJebZXoc3UgAdXxg7qaGc9AGVaZ GtJZxsVBVW46GSQkOk4GAQ89qRShVQrpWynH6YdD2kSsbKwKycryapmSVHoxbTfPs04t sw0sx+0IxkNcRxmAy4XmrMeLEHE7OTeiYHBUh3u2Cf3QQF/Zl/z//Y1aIbMULyUO30oB wGY45VHtdoATYap0TVPEnCcqQY+fkmhnUP8ami7DPFm3ItBDKeV4RzcppiY4pjfNcuAD f1pqBKONeL8Ae58OXvOuGnM5Jkbv/wbQTk47JtWSHJR9Aor94CrWNg3/kW1KHoEaiKfA zE6Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=Or9Dc22i/7f/YW0tvEwykVYSyBSv8lYxv1cGbeL+tYY=; b=U4a+ocvWCEf4MT9A8gDYYhDbJv1l0LsHZ4Fu24tT00lt6Mr9tmM2J+SQcVZzp0J/Pg Z9GBPh+xPejzPoOBgLDv78bfvjqYcqGvGKeCi+Nszz4q1Fz8ogiGMuBtqDqM7qqh/zvs sqze0ulTBaR6eCG5nE8XhfpUee9TEFSp/VaNmec+YHJnmzU4FzvLXvqvXBS7JBbChrtV vjvG+ikvX6Qgp+27Gyq/JsqGhT5IRX6xpErhXQtW2ssV8D5AobDBDS/o28zvNi/7pzwe 2sd7Zkvp34CehF1mKsT2ettDzDiqliChU+QXb8U97WqFu1i2XNrnwTKO2UztsIF1N41/ Sq/Q== X-Gm-Message-State: APjAAAVJYf7MFmZnz26DLaj9AT4R3BhT1BCI7b1AX01VMI13VwJs+Uc+ i7S+rpxY0pjUpcfxruj9Ix6jf5bsRQ== X-Google-Smtp-Source: APXvYqySWeHIYT3gM4LE6tLQKxjcIwMACvHv82ozZkl1Q2uA5IxL/HJvvNLVJ3NfQtyBkgQSVxyoRD6HNA== X-Received: by 2002:adf:db4c:: with SMTP id f12mr2777929wrj.379.1571321615653; Thu, 17 Oct 2019 07:13:35 -0700 (PDT) Date: Thu, 17 Oct 2019 16:13:00 +0200 In-Reply-To: <20191017141305.146193-1-elver@google.com> Message-Id: <20191017141305.146193-4-elver@google.com> Mime-Version: 1.0 References: <20191017141305.146193-1-elver@google.com> X-Mailer: git-send-email 2.23.0.866.gb869b98d4c-goog Subject: [PATCH v2 3/8] build, kcsan: Add KCSAN build exceptions 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@linux.ibm.com, peterz@infradead.org, tglx@linutronix.de, will@kernel.org, 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 Content-Type: text/plain; charset="UTF-8" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org This blacklists several compilation units from KCSAN. See the respective inline comments for the reasoning. Signed-off-by: Marco Elver --- kernel/Makefile | 5 +++++ kernel/sched/Makefile | 6 ++++++ mm/Makefile | 8 ++++++++ 3 files changed, 19 insertions(+) diff --git a/kernel/Makefile b/kernel/Makefile index 74ab46e2ebd1..4a597a68b8bc 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -23,6 +23,9 @@ endif # Prevents flicker of uninteresting __do_softirq()/__local_bh_disable_ip() # in coverage traces. KCOV_INSTRUMENT_softirq.o := n +# Avoid KCSAN instrumentation in softirq ("No shared variables, all the data +# are CPU local" => assume no data-races), to reduce overhead in interrupts. +KCSAN_SANITIZE_softirq.o = n # These are called from save_stack_trace() on slub debug path, # and produce insane amounts of uninteresting coverage. KCOV_INSTRUMENT_module.o := n @@ -30,6 +33,7 @@ KCOV_INSTRUMENT_extable.o := n # Don't self-instrument. KCOV_INSTRUMENT_kcov.o := n KASAN_SANITIZE_kcov.o := n +KCSAN_SANITIZE_kcov.o := n CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) # cond_syscall is currently not LTO compatible @@ -118,6 +122,7 @@ obj-$(CONFIG_RSEQ) += rseq.o obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o KASAN_SANITIZE_stackleak.o := n +KCSAN_SANITIZE_stackleak.o := n KCOV_INSTRUMENT_stackleak.o := n $(obj)/configs.o: $(obj)/config_data.gz diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile index 21fb5a5662b5..e9307a9c54e7 100644 --- a/kernel/sched/Makefile +++ b/kernel/sched/Makefile @@ -7,6 +7,12 @@ endif # that is not a function of syscall inputs. E.g. involuntary context switches. KCOV_INSTRUMENT := n +# There are numerous races here, however, most of them due to plain accesses. +# This would make it even harder for syzbot to find reproducers, because these +# bugs trigger without specific input. Disable by default, but should re-enable +# eventually. +KCSAN_SANITIZE := n + ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y) # According to Alan Modra , the -fno-omit-frame-pointer is # needed for x86 only. Why this used to be enabled for all architectures is beyond diff --git a/mm/Makefile b/mm/Makefile index d996846697ef..33ea0154dd2d 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -7,6 +7,14 @@ KASAN_SANITIZE_slab_common.o := n KASAN_SANITIZE_slab.o := n KASAN_SANITIZE_slub.o := n +# These produce frequent data-race reports: most of them are due to races on +# the same word but accesses to different bits of that word. Re-enable KCSAN +# for these when we have more consensus on what to do about them. +KCSAN_SANITIZE_slab_common.o := n +KCSAN_SANITIZE_slab.o := n +KCSAN_SANITIZE_slub.o := n +KCSAN_SANITIZE_page_alloc.o := n + # These files are disabled because they produce non-interesting and/or # flaky coverage that is not a function of syscall inputs. E.g. slab is out of # free pages, or a task is migrated between nodes. -- 2.23.0.866.gb869b98d4c-goog