Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751237AbdFBOh7 (ORCPT ); Fri, 2 Jun 2017 10:37:59 -0400 Received: from mail.kdab.com ([176.9.126.58]:44454 "EHLO mail.kdab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbdFBOh6 (ORCPT ); Fri, 2 Jun 2017 10:37:58 -0400 From: Milian Wolff To: Linux-kernel@vger.kernel.org Cc: linux-perf-users@vger.kernel.org, Milian Wolff , Arnaldo Carvalho de Melo , Namhyung Kim , Jiri Olsa Subject: [PATCH 1/2] perf report: ensure the perf DSO mapping matches what libdw sees Date: Fri, 2 Jun 2017 16:37:52 +0200 Message-Id: <20170602143753.16907-1-milian.wolff@kdab.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2271 Lines: 60 In some situations the libdw unwinder stopped working properly. I.e. with libunwind we see: ~~~~~ heaptrack_gui 2228 135073.400112: 641314 cycles: e8ed _dl_fixup (/usr/lib/ld-2.25.so) 15f06 _dl_runtime_resolve_sse_vex (/usr/lib/ld-2.25.so) ed94c KDynamicJobTracker::KDynamicJobTracker (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0) 608f3 _GLOBAL__sub_I_kdynamicjobtracker.cpp (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0) f199 call_init.part.0 (/usr/lib/ld-2.25.so) f2a5 _dl_init (/usr/lib/ld-2.25.so) db9 _dl_start_user (/usr/lib/ld-2.25.so) ~~~~~ But with libdw and without this patch this sample is not properly unwound: ~~~~~ heaptrack_gui 2228 135073.400112: 641314 cycles: e8ed _dl_fixup (/usr/lib/ld-2.25.so) 15f06 _dl_runtime_resolve_sse_vex (/usr/lib/ld-2.25.so) ed94c KDynamicJobTracker::KDynamicJobTracker (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0) ~~~~~ Debug output showed me that libdw found a module for the last frame address, but it thinks it belongs to /usr/lib/ld-2.25.so. This patch double-checks what libdw sees and what perf knows. If the mappings mismatch, we now report the elf known to perf. This fixes the situation above, and the libdw unwinder produces the same stack as libunwind. Cc: Arnaldo Carvalho de Melo Cc: Namhyung Kim Cc: Jiri Olsa Signed-off-by: Milian Wolff --- tools/perf/util/unwind-libdw.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c index b4c20124d2ee..da45c4be5fb3 100644 --- a/tools/perf/util/unwind-libdw.c +++ b/tools/perf/util/unwind-libdw.c @@ -39,6 +39,14 @@ static int __report_module(struct addr_location *al, u64 ip, return 0; mod = dwfl_addrmodule(ui->dwfl, ip); + if (mod) { + Dwarf_Addr s; + + dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL); + if (s != al->map->start) + mod = 0; + } + if (!mod) mod = dwfl_report_elf(ui->dwfl, dso->short_name, dso->long_name, -1, al->map->start, -- 2.13.0