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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 004E9C433EF for ; Thu, 23 Sep 2021 13:32:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA4EE610D1 for ; Thu, 23 Sep 2021 13:32:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241478AbhIWNd4 (ORCPT ); Thu, 23 Sep 2021 09:33:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:45942 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241467AbhIWNds (ORCPT ); Thu, 23 Sep 2021 09:33:48 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5F05D610D1; Thu, 23 Sep 2021 13:32:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1632403936; bh=TyNFPW4VpmUhkf1H5RUpWm9BcVpjiDxX+ppA9eB8jFU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=b2IdFQ9TiOg4ur5jxX7J1YI3vT1u/Cwy4X1Ocmtm3SKwThJjpfXCv0tVaC6Qgjn1j xUthEQjFAM5Hzw2z3FeONXCYCSdfx16T3IKaxFNqleoO1eou7Swn1pIiap5Ap9734V 3aZjQ9e3zlqtfcQq3rEJGAVkida7N8Oxr5K1Kt2ScTJwSJr5c/IYe8snJYBYkCaCIl crKzFfgq+SsLasAFrSG7Ipiu/NL5Gc0lpMhnXVursXoY24Ozhwp9DQQlCu3sUK2gut NS1ozVaj5bFIfd+EafaqfhTI93gACAqE1BtuuwnwrS6cbTgCRn6Xm9sAIUWLl+2hWx U2gSgM+onLTrg== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id C2E50410A1; Thu, 23 Sep 2021 10:32:13 -0300 (-03) Date: Thu, 23 Sep 2021 10:32:13 -0300 From: Arnaldo Carvalho de Melo To: Jiri Olsa Cc: Ian Rogers , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Namhyung Kim , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Ard Biesheuvel , Miguel Ojeda , Stephane Eranian Subject: Re: [PATCH v2] perf test: Fix dwarf unwind for optimized builds. Message-ID: References: <20210922173812.456348-1-irogers@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Thu, Sep 23, 2021 at 12:00:11AM +0200, Jiri Olsa escreveu: > On Wed, Sep 22, 2021 at 10:38:12AM -0700, Ian Rogers wrote: > > To ensure the stack frames are on the stack tail calls optimizations > > need to be inhibited. If your compiler supports an attribute use it, > > otherwise use an asm volatile barrier. > > > > The barrier fix was suggested here: > > https://lore.kernel.org/lkml/20201028081123.GT2628@hirez.programming.kicks-ass.net/ > > Tested with an optimized clang build and by forcing the asm barrier > > route with an optimized clang build. > > > > A GCC bug tracking a proper disable_tail_calls is: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97831 > > > > Fixes: 9ae1e990f1ab ("perf tools: Remove broken __no_tail_call > > attribute") > > > > v2. is a rebase. The original fix patch generated quite a lot of > > discussion over the right place for the fix: > > https://lore.kernel.org/lkml/20201114000803.909530-1-irogers@google.com/ > > The patch reflects my preference of it being near the use, so that > > future code cleanups don't break this somewhat special usage. > > Acked-by: Jiri Olsa Thanks, applied. - Arnaldo > thanks, > jirka > > > > > Signed-off-by: Ian Rogers > > --- > > tools/perf/tests/dwarf-unwind.c | 39 +++++++++++++++++++++++++++------ > > 1 file changed, 32 insertions(+), 7 deletions(-) > > > > diff --git a/tools/perf/tests/dwarf-unwind.c b/tools/perf/tests/dwarf-unwind.c > > index a288035eb362..c756284b3b13 100644 > > --- a/tools/perf/tests/dwarf-unwind.c > > +++ b/tools/perf/tests/dwarf-unwind.c > > @@ -20,6 +20,23 @@ > > /* For bsearch. We try to unwind functions in shared object. */ > > #include > > > > +/* > > + * The test will assert frames are on the stack but tail call optimizations lose > > + * the frame of the caller. Clang can disable this optimization on a called > > + * function but GCC currently (11/2020) lacks this attribute. The barrier is > > + * used to inhibit tail calls in these cases. > > + */ > > +#ifdef __has_attribute > > +#if __has_attribute(disable_tail_calls) > > +#define NO_TAIL_CALL_ATTRIBUTE __attribute__((disable_tail_calls)) > > +#define NO_TAIL_CALL_BARRIER > > +#endif > > +#endif > > +#ifndef NO_TAIL_CALL_ATTRIBUTE > > +#define NO_TAIL_CALL_ATTRIBUTE > > +#define NO_TAIL_CALL_BARRIER __asm__ __volatile__("" : : : "memory"); > > +#endif > > + > > static int mmap_handler(struct perf_tool *tool __maybe_unused, > > union perf_event *event, > > struct perf_sample *sample, > > @@ -91,7 +108,7 @@ static int unwind_entry(struct unwind_entry *entry, void *arg) > > return strcmp((const char *) symbol, funcs[idx]); > > } > > > > -noinline int test_dwarf_unwind__thread(struct thread *thread) > > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__thread(struct thread *thread) > > { > > struct perf_sample sample; > > unsigned long cnt = 0; > > @@ -122,7 +139,7 @@ noinline int test_dwarf_unwind__thread(struct thread *thread) > > > > static int global_unwind_retval = -INT_MAX; > > > > -noinline int test_dwarf_unwind__compare(void *p1, void *p2) > > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__compare(void *p1, void *p2) > > { > > /* Any possible value should be 'thread' */ > > struct thread *thread = *(struct thread **)p1; > > @@ -141,7 +158,7 @@ noinline int test_dwarf_unwind__compare(void *p1, void *p2) > > return p1 - p2; > > } > > > > -noinline int test_dwarf_unwind__krava_3(struct thread *thread) > > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_3(struct thread *thread) > > { > > struct thread *array[2] = {thread, thread}; > > void *fp = &bsearch; > > @@ -160,14 +177,22 @@ noinline int test_dwarf_unwind__krava_3(struct thread *thread) > > return global_unwind_retval; > > } > > > > -noinline int test_dwarf_unwind__krava_2(struct thread *thread) > > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_2(struct thread *thread) > > { > > - return test_dwarf_unwind__krava_3(thread); > > + int ret; > > + > > + ret = test_dwarf_unwind__krava_3(thread); > > + NO_TAIL_CALL_BARRIER; > > + return ret; > > } > > > > -noinline int test_dwarf_unwind__krava_1(struct thread *thread) > > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_1(struct thread *thread) > > { > > - return test_dwarf_unwind__krava_2(thread); > > + int ret; > > + > > + ret = test_dwarf_unwind__krava_2(thread); > > + NO_TAIL_CALL_BARRIER; > > + return ret; > > } > > > > int test__dwarf_unwind(struct test *test __maybe_unused, int subtest __maybe_unused) > > -- > > 2.33.0.464.g1972c5931b-goog > > -- - Arnaldo