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=ham 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 3CBAB7DCEA for ; Thu, 14 Nov 2019 18:04:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727265AbfKNSET (ORCPT ); Thu, 14 Nov 2019 13:04:19 -0500 Received: from mail-qk1-f202.google.com ([209.85.222.202]:35051 "EHLO mail-qk1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727376AbfKNSEP (ORCPT ); Thu, 14 Nov 2019 13:04:15 -0500 Received: by mail-qk1-f202.google.com with SMTP id r2so4513920qkb.2 for ; Thu, 14 Nov 2019 10:04:14 -0800 (PST) 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=96xEs+lJYo0V1womdbdeC7cnwgPWDGKGu93eR6OWopc=; b=IcRlS/dVG/yHoLpUqrFonkreYomsiHhkkrl6VYCjwGgeNozljGzE7fVKZv2Ssna1k8 1LzS+QCxkC5KHpnsTf2qXBJVStxBgXX4u/O4LQdZK9+jYIPMXHTqe6Nm3353E673RYzR tv5PgG6hmcfdvrqqaDTUgP4qJoJGJpLNU1xNJo6sFHJseHDw6SZ8fVh6/n4Br0qOJHh5 WJXazfV7vWPrPneFu9J2a4U+aToz+/wnOYE2oyh063VxBbUNpr06NyaV699hWg0WDYt2 YVnyTr7mGDVnEO2JcyvrLr/ihMtib36aaOFIiZNSTGvyzEB6gksmNZx1c054MGPXd/ng axNg== 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=96xEs+lJYo0V1womdbdeC7cnwgPWDGKGu93eR6OWopc=; b=KVoxca+uB2LqdBL+E58QalSpIovTmFAJv2C0MrTL0+Aizq0Ad1Qnhb+qhdtcqUlApO NAhkO7YlAAV7hTsUEi1Xw8g6Az0k7otNe8SsHQWG0jkbeq8mSQ2Vn7h2+xXgGzKFOFhs 9+khJN9Ocl7spciL06U3IxB2W5gv56zZvNyJA+zMIPHA1XSmlF96aGLLN4L7k+bYE+io NsmDtmhalsj5C/ALxdjuW14GPz1SoPXP0sfk426L/EQF3qH7Q7KWjkNRATWHIopE27Hr dKREvmjfA92/QBap/XREyWLT1gYAsO5uv9139VGtB+uRwtFnT/SjHKpqTqWlDIJvx8TW /9MQ== X-Gm-Message-State: APjAAAVHrQHJU2z+S61YE4Y/BjWhvwiD2OuAC66qH7bKPSmFbcBCbIFH 9JjbFAiL2FSuVWKG+G1b+Gk0PMv3rg== X-Google-Smtp-Source: APXvYqy9G23BfTtDP6DLRm/+dyC4HyMfQj+e3C86SeKn5yp6ansmdfintOUGctl96DGNbXdQ3o32tHVhbA== X-Received: by 2002:aed:2cc5:: with SMTP id g63mr9497984qtd.205.1573754653698; Thu, 14 Nov 2019 10:04:13 -0800 (PST) Date: Thu, 14 Nov 2019 19:02:58 +0100 In-Reply-To: <20191114180303.66955-1-elver@google.com> Message-Id: <20191114180303.66955-6-elver@google.com> Mime-Version: 1.0 References: <20191114180303.66955-1-elver@google.com> X-Mailer: git-send-email 2.24.0.rc1.363.gb1bccd3e3d-goog Subject: [PATCH v4 05/10] 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@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 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 Acked-by: Paul E. McKenney --- v3: * Moved EFI stub build exception hunk from x86-specific patch, since it's not x86-specific. * Spelling "data-race" -> "data race". --- drivers/firmware/efi/libstub/Makefile | 2 ++ kernel/Makefile | 5 +++++ kernel/sched/Makefile | 6 ++++++ mm/Makefile | 8 ++++++++ 4 files changed, 21 insertions(+) diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index ee0661ddb25b..5d0a645c0de8 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -31,7 +31,9 @@ KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ -D__DISABLE_EXPORTS GCOV_PROFILE := n +# Sanitizer runtimes are unavailable and cannot be linked here. KASAN_SANITIZE := n +KCSAN_SANITIZE := n UBSAN_SANITIZE := n OBJECT_FILES_NON_STANDARD := y diff --git a/kernel/Makefile b/kernel/Makefile index 74ab46e2ebd1..cc53f7c25446 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..56c1964bb3a1 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. -- 2.24.0.rc1.363.gb1bccd3e3d-goog