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=-23.3 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,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL 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 E0BE3C4743C for ; Mon, 21 Jun 2021 20:44:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C430F61245 for ; Mon, 21 Jun 2021 20:44:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231261AbhFUUqX (ORCPT ); Mon, 21 Jun 2021 16:46:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231246AbhFUUqW (ORCPT ); Mon, 21 Jun 2021 16:46:22 -0400 Received: from mail-lj1-x22b.google.com (mail-lj1-x22b.google.com [IPv6:2a00:1450:4864:20::22b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C73BEC061787 for ; Mon, 21 Jun 2021 13:44:07 -0700 (PDT) Received: by mail-lj1-x22b.google.com with SMTP id q23so16618897ljh.0 for ; Mon, 21 Jun 2021 13:44:07 -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=GM7eO0vh1gXIyPgCEQpkeMLnL2AEGJ5aVi0qEu4LSo8=; b=Tv/B3mY+3scUULk8gTsFxcANxIboIJw174bs0gw51AOv7A1ZRfIr7hYUaEHwg+ZizI fzmO0YHlj6H2lpoKGi7josGY9Mfw/HLy4ZAYuYJHFNtkAOa2Xk3HnV5PY9Q9nPzry3jo +MQPQ782m2lOvURjw5QugF45Uqk5mi8CTCsdS+oIFpsxhB/L/DenjvL24OwB1TGn2liQ ocgP7RiVl+Ur65AUVZVAg5q9cwhU9ngZMjOlYrqX2OIXbrgr7noecffzw21tqZBLwXgT AzfwivXbDZR8V/PQuBX7aXh8be1p52zDJJBdn6Ws/UOisqI1l5/6lhmWOuFBmYHOJ7XZ I8qA== 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=GM7eO0vh1gXIyPgCEQpkeMLnL2AEGJ5aVi0qEu4LSo8=; b=JLRxOOF1nKBiPWqmP3ETkd0p9X67E8/UZgOkegiI4W332PA9lDNUWPyN11gTRQQLh9 H9xvOcdgymNDWW8RSC+yO44bDrs/knwbnDQutg5yvOJOTkhlPOFwV9BgmPOsDGHpG5G1 BB+JsIXPLJP3hqbvn1T4vqFe5Fz67OgQzmEpl1WLb1D3/5QIPnfqsliRu9DsSH62a06i NDjGxqAmiZAKwtPRPuO3/CPfhjdd7iqHtmeMu4O0DbTG6dtuCGn0xcCux4eejzWB4Rg5 yhwjWqqQf2tWnrlOcwgMIL2jLDFHXhmsYf2wGTzCRYgqgRD6HQEtCzOL9Mq8f1F5j7WS OZ3Q== X-Gm-Message-State: AOAM531usnKdrffQJlukToW01N8HlBOsI2HqT2aH29TnmKVbO4V9Do8z JzT38vZ/JtAujXUcL9dvdTnRNafzvqwlDzad862cVg== X-Google-Smtp-Source: ABdhPJxfm+tu/X5s5KMcrvmuiAKdIXZg/zRgvhW5dsk/13kjWABpiROoHBqsKkjL8DZZ+gemFgG2p2a2kf8W3toM9/4= X-Received: by 2002:a05:651c:1181:: with SMTP id w1mr88154ljo.116.1624308245741; Mon, 21 Jun 2021 13:44:05 -0700 (PDT) MIME-Version: 1.0 References: <20210618233023.1360185-1-ndesaulniers@google.com> <20210618233023.1360185-3-ndesaulniers@google.com> In-Reply-To: From: Nick Desaulniers Date: Mon, 21 Jun 2021 13:43:54 -0700 Message-ID: Subject: Re: [PATCH 2/2] Kconfig: CC_HAS_NO_PROFILE_FN_ATTR, depend on for GCOV and PGO To: Bill Wendling , Masahiro Yamada Cc: Will Deacon , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Peter Oberparleiter , Kees Cook , Peter Zijlstra , Bill Wendling , Sami Tolvanen , Miguel Ojeda , Nathan Chancellor , Luc Van Oostenryck , Arnd Bergmann , Andrew Morton , Rasmus Villemoes , LKML , clang-built-linux , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Borislav Petkov , Martin Liska , Jonathan Corbet , Fangrui Song , Linux Doc Mailing List , Linux Kbuild mailing list , Dmitry Vyukov , Johannes Berg , linux-toolchains@vger.kernel.org, Marco Elver , Linux ARM , linux-s390 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-toolchains@vger.kernel.org On Mon, Jun 21, 2021 at 11:50 AM Bill Wendling wrote: > > On Mon, Jun 21, 2021 at 11:22 AM Nick Desaulniers > wrote: > > > > On Fri, Jun 18, 2021 at 11:23 PM Marco Elver wrote: > > > > > > On Sat, 19 Jun 2021 at 01:30, Nick Desaulniers wrote: > > > > > > > > We don't want compiler instrumentation to touch noinstr functions, which > > > > are annotated with the no_profile function attribute. Add a Kconfig test > > > > for this and make PGO and GCOV depend on it. > > > > > > > > Cc: Masahiro Yamada > > > > Cc: Peter Oberparleiter > > > > Link: https://lore.kernel.org/lkml/YMTn9yjuemKFLbws@hirez.programming.kicks-ass.net/ > > > > Link: https://lore.kernel.org/lkml/YMcssV%2Fn5IBGv4f0@hirez.programming.kicks-ass.net/ > > > > Suggested-by: Peter Zijlstra > > > > Signed-off-by: Nick Desaulniers > > > > --- > > > > init/Kconfig | 3 +++ > > > > kernel/gcov/Kconfig | 1 + > > > > kernel/pgo/Kconfig | 3 ++- > > > > 3 files changed, 6 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/init/Kconfig b/init/Kconfig > > > > index 1ea12c64e4c9..540f862b40c6 100644 > > > > --- a/init/Kconfig > > > > +++ b/init/Kconfig > > > > @@ -83,6 +83,9 @@ config TOOLS_SUPPORT_RELR > > > > config CC_HAS_ASM_INLINE > > > > def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) > > > > > > > > +config CC_HAS_NO_PROFILE_FN_ATTR > > > > + def_bool $(success,echo '__attribute__((no_profile)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) > > > > + > > > > config CONSTRUCTORS > > > > bool > > > > > > > > diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig > > > > index 58f87a3092f3..19facd4289cd 100644 > > > > --- a/kernel/gcov/Kconfig > > > > +++ b/kernel/gcov/Kconfig > > > > @@ -5,6 +5,7 @@ config GCOV_KERNEL > > > > bool "Enable gcov-based kernel profiling" > > > > depends on DEBUG_FS > > > > depends on !CC_IS_CLANG || CLANG_VERSION >= 110000 > > > > + depends on !X86 || (X86 && CC_HAS_NO_PROFILE_FN_ATTR) > > > > > > [+Cc Mark] > > > > > > arm64 is also starting to rely on noinstr working properly. > > > > Sure, > > Will, Catalin, other arm64 folks: > > Any thoughts on requiring GCC 7.1+/Clang 13.0+ for GCOV support? That > > way we can better guarantee that GCOV (and eventually, PGO) don't > > touch noinstr functions? > > > > If that's ok, I'll add modify the above like: > > > > + depends on !ARM64 || (ARM64 && CC_HAS_NO_PROFILE_FN_ATTR) > > > Wouldn't "!ARM64 || CC_HAS_NO_PROFILE_FN_ATTR" be more succinct? We need to be able to express via Kconfig "GCOV should not be enabled for architectures that use noinstr when the toolchain does not support __attribute__((no_profile_instrument_function))." Where "architectures that use noinstr" are currently arm64, s390, and x86. So I guess we could do: + depends on !ARM64 || !S390 || !X86 || CC_HAS_NO_PROFILE_FN_ATTR (We could add a Kconfig for ARCH_WANTS_NO_INSTR, which might be more informative than listed out architectures which might be non-obvious to passers-by). It would be most succinct to raise the requirements to: "GCOV should not be enabled when the toolchain does not support __attribute__((no_profile_instrument_function))." Then we could do: + depends on CC_HAS_NO_PROFILE_FN_ATTR Assuming no one has the requirement to support GCOV on PPC with GCC < 7.1, for example. > > > to the above hunk in v2. Oh, looks like arch/s390 also uses noinstr. > > Same question applies then: > > > > + depends on !S390 || (S390 && CC_HAS_NO_PROFILE_FN_ATTR) > > > > Or, we could just do > > > > + depends on CC_HAS_NO_PROFILE_FN_ATTR > > > > Though that will penalize architectures not using noinstr, that still > > would like to use GCOV with versions of GCC older than 7.1. Perhaps > > there are no such such users, or they should consider upgrading their > > tools to we can stick with the simpler Kconfig? Thoughts? > > > > > > > > This should probably be a 'select ARCH_HAS_GCOV_PROFILE_ALL if > > > CC_HAS_NO_PROFILE_FN_ATTR' in the relevant arch/../Kconfig. > > > > > > Alternatively, using: > > > https://lkml.kernel.org/r/YMcssV/n5IBGv4f0@hirez.programming.kicks-ass.net > > > > > > But I'd probably not overcomplicate things at this point and just use > > > ARCH_HAS_GCOV_PROFILE_ALL, because GCOV seems to be a) rarely used, > > > and b) if someone decides to selectively instrument stuff like entry > > > code, we can just say it's user error. > > > > > > > > > > select CONSTRUCTORS > > > > default n > > > > help > > > > diff --git a/kernel/pgo/Kconfig b/kernel/pgo/Kconfig > > > > index d2053df1111c..26f75ac4c6c1 100644 > > > > --- a/kernel/pgo/Kconfig > > > > +++ b/kernel/pgo/Kconfig > > > > @@ -8,7 +8,8 @@ config PGO_CLANG > > > > bool "Enable clang's PGO-based kernel profiling" > > > > depends on DEBUG_FS > > > > depends on ARCH_SUPPORTS_PGO_CLANG > > > > - depends on CC_IS_CLANG && CLANG_VERSION >= 120000 > > > > + depends on CC_IS_CLANG > > > > + depends on CC_HAS_NO_PROFILE_FN_ATTR > > > > help > > > > This option enables clang's PGO (Profile Guided Optimization) based > > > > code profiling to better optimize the kernel. > > > > -- > > > > 2.32.0.288.g62a8d224e6-goog > > > > > > > > > > > > -- > > Thanks, > > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers