From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757295AbaHZGit (ORCPT ); Tue, 26 Aug 2014 02:38:49 -0400 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:59704 "EHLO lgemrelse7q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757212AbaHZGir (ORCPT ); Tue, 26 Aug 2014 02:38:47 -0400 X-Original-SENDERIP: 10.177.220.181 X-Original-MAILFROM: namhyung@kernel.org From: Namhyung Kim To: Arnaldo Carvalho de Melo Cc: Peter Zijlstra , Ingo Molnar , Paul Mackerras , Namhyung Kim , Namhyung Kim , LKML , Jiri Olsa , David Ahern , Adrian Hunter , Andi Kleen , Stephane Eranian , stable@vger.kernel.org Subject: [PATCH] perf tools: Fix build-id matching on vmlinux Date: Tue, 26 Aug 2014 15:38:39 +0900 Message-Id: <1409035119-24357-1-git-send-email-namhyung@kernel.org> X-Mailer: git-send-email 2.0.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There's a problem on finding correct kernel symbols when perf report runs on a different kernel. Although a part of the problem was solved by the prior commit 0a7e6d1b6844 ("perf tools: Check recorded kernel version when finding vmlinux"), there's a remaining problem still. When perf records samples, it synthesizes the kernel map using machine__mmap_name() and ref_reloc_sym like "[kernel.kallsyms]_text". You can easily see it using 'perf report -D' command. After finishing record, it goes through the recorded events to find maps/dsos actually used. And then record build-id info of them. During this process, it needs to load symbols in a dso and it'd call dso__load_vmlinux() since the default value of the symbol_conf.try_ vmlinux_path is true. However it changes dso->long_name to a real path of the vmlinux file (e.g. /lib/modules/3.16.0-rc2+/build/vmlinux) if one is running on a custom kernel. It resulted in that perf report reads the build-id of the vmlinux, but cannot use it since it only knows about the [kernel.kallsyms] map. It then falls back to possible vmlinux paths by using the recorded kernel version (in case of a recent version) or a running kernel silently (which might break the result). I think it's worth going to the stable tree. I can think of a couple of ways to fix it. In this patch, I changed to use the name of "[kernel.kallsyms]" for the kernel build-id event instead of not trying vmlinux paths. This way we can provide maximum info (like annotation) with minimum change IMHO. Before: $ perf record -a usleep 1 $ perf buildid-list 00d5ff078efe1d30b8492854f259215fd877ce30 /lib/modules/3.16.0-rc2+/build/vmlinux 78186287bba77069a056a5ccbeb14b7fd2ca3a4b /usr/lib64/libc-2.17.so 4eadca6cb82e0a85edb87c15b5e3980742514501 /usr/lib64/ld-2.17.so 1e272ca30081e81ef41935a630eb2f4c636798b4 /usr/lib64/dri/swrast_dri.so $ perf buildid-list -H 0000000000000000000000000000000000000000 [kernel.kallsyms] 78186287bba77069a056a5ccbeb14b7fd2ca3a4b /usr/lib64/libc-2.17.so 4eadca6cb82e0a85edb87c15b5e3980742514501 /usr/lib64/ld-2.17.so 1e272ca30081e81ef41935a630eb2f4c636798b4 /usr/lib64/dri/swrast_dri.so 0000000000000000000000000000000000000000 /tmp/perf-2523.map After: $ perf record -a usleep 1 $ perf buildid-list 00d5ff078efe1d30b8492854f259215fd877ce30 [kernel.kallsyms] 78186287bba77069a056a5ccbeb14b7fd2ca3a4b /usr/lib64/libc-2.17.so 4eadca6cb82e0a85edb87c15b5e3980742514501 /usr/lib64/ld-2.17.so 1e272ca30081e81ef41935a630eb2f4c636798b4 /usr/lib64/dri/swrast_dri.so $ perf buildid-list -H 00d5ff078efe1d30b8492854f259215fd877ce30 [kernel.kallsyms] 78186287bba77069a056a5ccbeb14b7fd2ca3a4b /usr/lib64/libc-2.17.so 4eadca6cb82e0a85edb87c15b5e3980742514501 /usr/lib64/ld-2.17.so 1e272ca30081e81ef41935a630eb2f4c636798b4 /usr/lib64/dri/swrast_dri.so 0000000000000000000000000000000000000000 /tmp/perf-2523.map Cc: stable@vger.kernel.org Signed-off-by: Namhyung Kim --- tools/perf/util/header.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c index 158c787ce0c4..5c4093dee467 100644 --- a/tools/perf/util/header.c +++ b/tools/perf/util/header.c @@ -263,6 +263,9 @@ static int __dsos__write_buildid_table(struct list_head *head, machine__mmap_name(machine, nm, sizeof(nm)); name = nm; name_len = strlen(nm) + 1; + } else if (dso__is_vmlinux(pos)) { + name = pos->name; + name_len = strlen(pos->name) + 1; } else { name = pos->long_name; name_len = pos->long_name_len + 1; -- 2.0.0