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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_RED 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 1A079C11F69 for ; Thu, 1 Jul 2021 01:56:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 06D4C61480 for ; Thu, 1 Jul 2021 01:56:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238570AbhGAB7V (ORCPT ); Wed, 30 Jun 2021 21:59:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:49238 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238569AbhGAB7V (ORCPT ); Wed, 30 Jun 2021 21:59:21 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CF31761477; Thu, 1 Jul 2021 01:56:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1625104610; bh=tVj8h0/d1Wc7454HiRxxN7FOSqp9osNr9V232lwKMJQ=; h=Date:From:To:Subject:In-Reply-To:From; b=zO1FMPi0Vdq3JJJBlwob3qb52rps/N5wx27Wg0AZM8PkD1C9czcASqoxu0Zgg7Hp0 fBXxGRiyypD5YJ8Mx9zhz6dqg0aXwTFRoPZqmeeHJGWhdjZjIFOIySJ2lh+/VpaGzB 8EYJ5fa3cwty7YPjN5fP0dyayvr/jCBDcQDB7MNo= Date: Wed, 30 Jun 2021 18:56:49 -0700 From: Andrew Morton To: akpm@linux-foundation.org, ardb@kernel.org, arnd@arndb.de, dvyukov@google.com, elver@google.com, keescook@chromium.org, linux-mm@kvack.org, luc.vanoostenryck@gmail.com, mark.rutland@arm.com, masahiroy@kernel.org, mm-commits@vger.kernel.org, nathan@kernel.org, ndesaulniers@google.com, nivedita@alum.mit.edu, ojeda@kernel.org, peterz@infradead.org, samitolvanen@google.com, torvalds@linux-foundation.org, will@kernel.org Subject: [patch 183/192] kcov: add __no_sanitize_coverage to fix noinstr for all architectures Message-ID: <20210701015649.5yaBp3d6B%akpm@linux-foundation.org> In-Reply-To: <20210630184624.9ca1937310b0dd5ce66b30e7@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Marco Elver Subject: kcov: add __no_sanitize_coverage to fix noinstr for all architectures Until now no compiler supported an attribute to disable coverage instrumentation as used by KCOV. To work around this limitation on x86, noinstr functions have their coverage instrumentation turned into nops by objtool. However, this solution doesn't scale automatically to other architectures, such as arm64, which are migrating to use the generic entry code. Clang [1] and GCC [2] have added support for the attribute recently. [1] https://github.com/llvm/llvm-project/commit/280333021e9550d80f5c1152a34e33e81df1e178 [2] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=cec4d4a6782c9bd8d071839c50a239c49caca689 The changes will appear in Clang 13 and GCC 12. Add __no_sanitize_coverage for both compilers, and add it to noinstr. Note: In the Clang case, __has_feature(coverage_sanitizer) is only true if the feature is enabled, and therefore we do not require an additional defined(CONFIG_KCOV) (like in the GCC case where __has_attribute(..) is always true) to avoid adding redundant attributes to functions if KCOV is off. That being said, compilers that support the attribute will not generate errors/warnings if the attribute is redundantly used; however, where possible let's avoid it as it reduces preprocessed code size and associated compile-time overheads. [elver@google.com: Implement __has_feature(coverage_sanitizer) in Clang] Link: https://lkml.kernel.org/r/20210527162655.3246381-1-elver@google.com [elver@google.com: add comment explaining __has_feature() in Clang] Link: https://lkml.kernel.org/r/20210527194448.3470080-1-elver@google.com Link: https://lkml.kernel.org/r/20210525175819.699786-1-elver@google.com Signed-off-by: Marco Elver Acked-by: Peter Zijlstra (Intel) Reviewed-by: Miguel Ojeda Reviewed-by: Nathan Chancellor Cc: Nick Desaulniers Cc: Kees Cook Cc: Will Deacon Cc: Ard Biesheuvel Cc: Luc Van Oostenryck Cc: Arvind Sankar Cc: Masahiro Yamada Cc: Sami Tolvanen Cc: Arnd Bergmann Cc: Dmitry Vyukov Cc: Mark Rutland Signed-off-by: Andrew Morton --- include/linux/compiler-clang.h | 17 +++++++++++++++++ include/linux/compiler-gcc.h | 6 ++++++ include/linux/compiler_types.h | 2 +- 3 files changed, 24 insertions(+), 1 deletion(-) --- a/include/linux/compiler-clang.h~kcov-add-__no_sanitize_coverage-to-fix-noinstr-for-all-architectures +++ a/include/linux/compiler-clang.h @@ -13,6 +13,12 @@ /* all clang versions usable with the kernel support KASAN ABI version 5 */ #define KASAN_ABI_VERSION 5 +/* + * Note: Checking __has_feature(*_sanitizer) is only true if the feature is + * enabled. Therefore it is not required to additionally check defined(CONFIG_*) + * to avoid adding redundant attributes in other configurations. + */ + #if __has_feature(address_sanitizer) || __has_feature(hwaddress_sanitizer) /* Emulate GCC's __SANITIZE_ADDRESS__ flag */ #define __SANITIZE_ADDRESS__ @@ -46,6 +52,17 @@ #endif /* + * Support for __has_feature(coverage_sanitizer) was added in Clang 13 together + * with no_sanitize("coverage"). Prior versions of Clang support coverage + * instrumentation, but cannot be queried for support by the preprocessor. + */ +#if __has_feature(coverage_sanitizer) +#define __no_sanitize_coverage __attribute__((no_sanitize("coverage"))) +#else +#define __no_sanitize_coverage +#endif + +/* * Not all versions of clang implement the type-generic versions * of the builtin overflow checkers. Fortunately, clang implements * __has_builtin allowing us to avoid awkward version --- a/include/linux/compiler-gcc.h~kcov-add-__no_sanitize_coverage-to-fix-noinstr-for-all-architectures +++ a/include/linux/compiler-gcc.h @@ -122,6 +122,12 @@ #define __no_sanitize_undefined #endif +#if defined(CONFIG_KCOV) && __has_attribute(__no_sanitize_coverage__) +#define __no_sanitize_coverage __attribute__((no_sanitize_coverage)) +#else +#define __no_sanitize_coverage +#endif + #if GCC_VERSION >= 50100 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 #endif --- a/include/linux/compiler_types.h~kcov-add-__no_sanitize_coverage-to-fix-noinstr-for-all-architectures +++ a/include/linux/compiler_types.h @@ -210,7 +210,7 @@ struct ftrace_likely_data { /* Section for code which can't be instrumented at all */ #define noinstr \ noinline notrace __attribute((__section__(".noinstr.text"))) \ - __no_kcsan __no_sanitize_address + __no_kcsan __no_sanitize_address __no_sanitize_coverage #endif /* __KERNEL__ */ _