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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 D841DC433E0 for ; Wed, 13 Jan 2021 10:47:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6BD9823122 for ; Wed, 13 Jan 2021 10:47:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726523AbhAMKrx (ORCPT ); Wed, 13 Jan 2021 05:47:53 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:45904 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726444AbhAMKrw (ORCPT ); Wed, 13 Jan 2021 05:47:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610534786; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ec0y/BdJxRfTy0k6b2igIfk1/DDD0lJc0nWam9VBkXg=; b=ioNcbNlZHjI44f9y0aWreo5feCpdiMFu7NOf7QlYhEdt5Qvy9X8i5pu8/IOI/+QNK0Ucy7 by/B9VCJ4J+lQyOLAyCMSJll2ILCkP8YDxnnoDdNDMKYhJovMDeUaVCT3evuesC/R529ut UXiX2K62sWzxu36bA67rrkkAVRb1dYw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-583-TJW31ew2Ps2czLwl7amhYg-1; Wed, 13 Jan 2021 05:46:22 -0500 X-MC-Unique: TJW31ew2Ps2czLwl7amhYg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 100E68144E0; Wed, 13 Jan 2021 10:46:21 +0000 (UTC) Received: from krava (unknown [10.40.195.134]) by smtp.corp.redhat.com (Postfix) with SMTP id 4C9F95D9DC; Wed, 13 Jan 2021 10:46:18 +0000 (UTC) Date: Wed, 13 Jan 2021 11:46:18 +0100 From: Jiri Olsa To: Jiri Slaby Cc: acme@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Namhyung Kim Subject: Re: [PATCH] perf tools: Resolve symbols against debug file first Message-ID: <20210113104618.GB1331835@krava> References: <20210113080128.10286-1-jslaby@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210113080128.10286-1-jslaby@suse.cz> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 13, 2021 at 09:01:28AM +0100, Jiri Slaby wrote: > With LTO, there are symbols like these: > /usr/lib/debug/usr/lib64/libantlr4-runtime.so.4.8-4.8-1.4.x86_64.debug > 10305: 0000000000955fa4 0 NOTYPE LOCAL DEFAULT 29 Predicate.cpp.2bc410e7 > > This comes from a runtime/debug split done by the standard way: > objcopy --only-keep-debug $runtime $debug > objcopy --add-gnu-debuglink=$debugfn -R .comment -R .GCC.command.line --strip-all $runtime > > perf currently cannot resolve such symbols (relicts of LTO), as section > 29 exists only in the debug file (29 is .debug_info). And perf resolves > symbols only against runtime file. This results in all symbols from such > a library being unresolved: > 0.38% main2 libantlr4-runtime.so.4.8 [.] 0x00000000000671e0 > > So try resolving against the debug file first. And only if it fails (the > section has NOBITS set), try runtime file. We can do this, as "objcopy > --only-keep-debug" per documentation preserves all sections, but clears > data of some of them (the runtime ones) and marks them as NOBITS. > > The correct result is now: > 0.38% main2 libantlr4-runtime.so.4.8 [.] antlr4::IntStream::~IntStream > > Note that these LTO symbols are properly skipped anyway as they belong > neither to *text* nor to *data* (is_label && !elf_sec__filter(&shdr, > secstrs) is true). > > Signed-off-by: Jiri Slaby > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Arnaldo Carvalho de Melo > Cc: Mark Rutland > Cc: Alexander Shishkin > Cc: Jiri Olsa > Cc: Namhyung Kim > --- > tools/perf/util/symbol-elf.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c > index f3577f7d72fe..a31b716fa61c 100644 > --- a/tools/perf/util/symbol-elf.c > +++ b/tools/perf/util/symbol-elf.c > @@ -1226,12 +1226,20 @@ int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss, > if (sym.st_shndx == SHN_ABS) > continue; > > - sec = elf_getscn(runtime_ss->elf, sym.st_shndx); > + sec = elf_getscn(syms_ss->elf, sym.st_shndx); > if (!sec) > goto out_elf_end; we iterate symbols from syms_ss, so the fix seems to be correct to call elf_getscn on syms_ss, not on runtime_ss as we do now I'd think this worked only when runtime_ss == syms_ss > > gelf_getshdr(sec, &shdr); > > + if (shdr.sh_type == SHT_NOBITS) { > + sec = elf_getscn(runtime_ss->elf, sym.st_shndx); > + if (!sec) > + goto out_elf_end; > + > + gelf_getshdr(sec, &shdr); > + } is that fallback necessary? the symbol is from syms_ss Namhyung, any idea? thanks, jirka