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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 99F58C433E0 for ; Wed, 13 Jan 2021 08:02:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5010F23120 for ; Wed, 13 Jan 2021 08:02:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726510AbhAMICM (ORCPT ); Wed, 13 Jan 2021 03:02:12 -0500 Received: from mx2.suse.de ([195.135.220.15]:46806 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725809AbhAMICL (ORCPT ); Wed, 13 Jan 2021 03:02:11 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 8F25FAE40; Wed, 13 Jan 2021 08:01:29 +0000 (UTC) From: Jiri Slaby To: acme@kernel.org Cc: linux-kernel@vger.kernel.org, Jiri Slaby , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim Subject: [PATCH] perf tools: Resolve symbols against debug file first Date: Wed, 13 Jan 2021 09:01:28 +0100 Message-Id: <20210113080128.10286-1-jslaby@suse.cz> X-Mailer: git-send-email 2.30.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; 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); + } + if (is_label && !elf_sec__filter(&shdr, secstrs)) continue; -- 2.30.0