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=-28.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, 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,USER_IN_DEF_DKIM_WL autolearn=ham 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 7C13CC47080 for ; Tue, 1 Jun 2021 17:47:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5FC7D613D2 for ; Tue, 1 Jun 2021 17:47:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234505AbhFARsn (ORCPT ); Tue, 1 Jun 2021 13:48:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43592 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231331AbhFARsm (ORCPT ); Tue, 1 Jun 2021 13:48:42 -0400 Received: from mail-lf1-x12b.google.com (mail-lf1-x12b.google.com [IPv6:2a00:1450:4864:20::12b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5991EC061574 for ; Tue, 1 Jun 2021 10:47:00 -0700 (PDT) Received: by mail-lf1-x12b.google.com with SMTP id x38so23093653lfa.10 for ; Tue, 01 Jun 2021 10:47:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=jJYP1ahOHUDkEz4I2iYxmBxvA/YEgFvm6f/leHoOsVY=; b=uiisl/l2JAeeqyGsUirCfSyUuUVpC8Cfit36EJ+bP2ODPTY7wxHgP0BQmI5rHxhTY9 LbJTI6WRjpjYGzpNwaOxqr6d7GSJnRpo+o1iVKkG0xUFVi7v3lmS5lLTRM4le9l4botv yb/lYPJKPLxS6ZbEdq69Yj5yZIgEUa+RdqMg4bJ8B4Vfe/M4ybKPhrZwW8ZFgr2tQInN uwTSyR7MUp+ysnFEOyUgaIuszyz0531mGUwp7h0eGYilZYVVX0Dm2TgvSAkimrIaEzRX Q9OP9icLpFN8qXEnagMF2oBO+ou8qmSVs5yuHmh0DNud2zh4Hl+K7BShc36iIkUaP4rr 9hWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=jJYP1ahOHUDkEz4I2iYxmBxvA/YEgFvm6f/leHoOsVY=; b=a/21lTKqlaUiag4OzplRxO9oRehG6vh8XMBzooTrJ6+EChHztH+xq2j/1/Zg5STMkf xIdBcNMji947kxOyFC5BY8ePaL73HGYidwqhLnYSZWS7BvXzR4jm2kpYV4gxMgGm3CY2 Q5XzfA3PVIlzJVs6EjRyjp5Dyu0COYHbfBxfiJmb4R0GRUA4MWcRiqupjSdWZEc/UAwL 4UXci9RQPVjZ2wJv8FfMHaORGETcgODbWfcjSO4LwFJcEZDQXB9Kby2Z7thgn694F+D6 XTTVPPXSjbmc+12xbFC0CtmfNQ/pBaj7f/GvzOYC6kYHG3KWSEbZzeWpOk1vmonwq1pZ oDsw== X-Gm-Message-State: AOAM532G68v5q8T8H2kx4LwdaiEWZGVb9bN6GM/gDnJd6BsFofTChSN7 MjmAfaqM5o+1NtfGN8ZHmz2/aWmuC0DwyKrdA46XeUbQURQ= X-Google-Smtp-Source: ABdhPJw42vulKDibjXHniD1a5KBQ7FuDHO9ORXGzCVu1stGaMi5omtQP2h7TLf4fg+sYsaNxhkBj+xxxGDJcXv2pTZw= X-Received: by 2002:a19:dc08:: with SMTP id t8mr8284937lfg.503.1622569618435; Tue, 01 Jun 2021 10:46:58 -0700 (PDT) MIME-Version: 1.0 References: <20210527162655.3246381-1-elver@google.com> In-Reply-To: From: Marco Elver Date: Tue, 1 Jun 2021 19:46:47 +0200 Message-ID: Subject: Re: [PATCH v2] kcov: add __no_sanitize_coverage to fix noinstr for all architectures To: Nick Desaulniers Cc: Andrew Morton , LKML , Nathan Chancellor , Miguel Ojeda , Peter Zijlstra , Kees Cook , Arvind Sankar , Will Deacon , Luc Van Oostenryck , Masahiro Yamada , Borislav Petkov , Sami Tolvanen , Arnd Bergmann , clang-built-linux , Dmitry Vyukov , Mark Rutland , kasan-dev Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 1 Jun 2021 at 19:42, Nick Desaulniers wrote: > On Thu, May 27, 2021 at 9:27 AM Marco Elver wrote: > > > > 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. > > > > Signed-off-by: Marco Elver > > Acked-by: Peter Zijlstra (Intel) > > --- > > v2: > > * Implement __has_feature(coverage_sanitizer) in Clang > > (https://reviews.llvm.org/D103159) and use instead of version check. > > * Add Peter's Ack. > > --- > > include/linux/compiler-clang.h | 11 +++++++++++ > > include/linux/compiler-gcc.h | 6 ++++++ > > include/linux/compiler_types.h | 2 +- > > 3 files changed, 18 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h > > index adbe76b203e2..e15eebfa8e5d 100644 > > --- a/include/linux/compiler-clang.h > > +++ b/include/linux/compiler-clang.h > > @@ -45,6 +45,17 @@ > > #define __no_sanitize_undefined > > #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. > > I'm not against a version check for supporting older releases (in > addition to the cleaner feature check, since the feature check was > non-existent); we can clean it up someday when clang-13 is the > minimally supported version. Would having an additional version check > help support existing/older releases here? The feature check will just return 0 on older releases, since the feature does not exist there. Therefore, no additional code is required to support older releases and a version check would be redundant. > > + */ > > +#if __has_feature(coverage_sanitizer) > > +#define __no_sanitize_coverage __attribute__((no_sanitize("coverage"))) > > +#else > > +#define __no_sanitize_coverage > > +#endif > > + Thanks, -- Marco