From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: symbol addresses are wrong when kcore is used Date: Tue, 8 Nov 2016 09:54:58 -0700 Message-ID: <7ab497c9-7b56-1fa2-2c7d-98f2199df993@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pf0-f193.google.com ([209.85.192.193]:33525 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752851AbcKHQzC (ORCPT ); Tue, 8 Nov 2016 11:55:02 -0500 Received: by mail-pf0-f193.google.com with SMTP id 144so11805743pfv.0 for ; Tue, 08 Nov 2016 08:55:01 -0800 (PST) Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Perf Users , Adrian Hunter , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim Hi guys: I have been meaning to ask about this for 2 years now: perf script shows the wrong addresses when /proc/kcore is referenced. Here's an example with perf from net-next tree (4.9-rc3): $ perf record -a -g -e fib6:* -- sleep 5 $ perf script vhost-7489 7491 [018] 2314.004488: fib6:fib6_table_lookup: table 255 oif 0 iif 4 src 2100:1::3 dst ff02::1:ff00:64 tos 0 scope 0 flags 0 ==> dev br1 gw :: 7fff8155f49e ip6_pol_route+0x80007f00249e ([kernel.kallsyms]) 7fff8155f77a ip6_pol_route_input+0x80007f00201a ([kernel.kallsyms]) 7fff81588515 fib6_rule_action+0x80007f0020c5 ([kernel.kallsyms]) 7fff814c2676 fib_rules_lookup+0x80007f002116 ([kernel.kallsyms]) 7fff815886b9 fib6_rule_lookup+0x80007f002059 ([kernel.kallsyms]) 7fff8155c77e ip6_route_input_lookup+0x80007f00204e ([kernel.kallsyms]) 7fff81560a98 ip6_route_input+0x80007f0020d8 ([kernel.kallsyms]) 7fff81550a92 ip6_rcv_finish+0x80007f002082 ([kernel.kallsyms]) 7fff81551344 ipv6_rcv+0x80007f002334 ([kernel.kallsyms]) The 7fff addresses are completely wrong. If I compile perf and disable use of kcore: diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index aecff69a510d..0debd7e96aa2 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -1285,7 +1285,7 @@ int __dso__load_kallsyms(struct dso *dso, const char *filename, int dso__load_kallsyms(struct dso *dso, const char *filename, struct map *map) { - return __dso__load_kallsyms(dso, filename, map, false); + return __dso__load_kallsyms(dso, filename, map, true); } static int dso__load_perf_map(struct dso *dso, struct map *map) Then the addresses are correct: vhost-7489 7491 [018] 2314.004488: fib6:fib6_table_lookup: table 255 oif 0 iif 4 src 2100:1::3 dst ff02::1:ff00:64 tos 0 scope 0 flags 0 ==> dev br1 gw :: ffffffff8155d49e ip6_pol_route+0x49e ([kernel.kallsyms]) ffffffff8155d77a ip6_pol_route_input+0x1a ([kernel.kallsyms]) ffffffff81586515 fib6_rule_action+0xc5 ([kernel.kallsyms]) ffffffff814c0676 fib_rules_lookup+0x116 ([kernel.kallsyms]) ffffffff815866b9 fib6_rule_lookup+0x59 ([kernel.kallsyms]) ffffffff8155a77e ip6_route_input_lookup+0x4e ([kernel.kallsyms]) ffffffff8155ea98 ip6_route_input+0xd8 ([kernel.kallsyms]) ffffffff8154ea92 ip6_rcv_finish+0x82 ([kernel.kallsyms]) ffffffff8154f344 ipv6_rcv+0x334 ([kernel.kallsyms]) Or if I cat kallsyms into a file and pass it to perf it works: $ cat /proc/kallsyms > /tmp/kallsyms $ perf script --kallsyms /tmp/kallsyms vhost-7489 7491 [018] 2314.004488: fib6:fib6_table_lookup: table 255 oif 0 iif 4 src 2100:1::3 dst ff02::1:ff00:64 tos 0 scope 0 flags 0 ==> dev br1 gw :: ffffffff8155d49e ip6_pol_route+0x49e ([kernel.kallsyms]) ffffffff8155d77a ip6_pol_route_input+0x1a ([kernel.kallsyms]) ffffffff81586515 fib6_rule_action+0xc5 ([kernel.kallsyms]) ffffffff814c0676 fib_rules_lookup+0x116 ([kernel.kallsyms]) ffffffff815866b9 fib6_rule_lookup+0x59 ([kernel.kallsyms]) ffffffff8155a77e ip6_route_input_lookup+0x4e ([kernel.kallsyms]) ffffffff8155ea98 ip6_route_input+0xd8 ([kernel.kallsyms]) ffffffff8154ea92 ip6_rcv_finish+0x82 ([kernel.kallsyms]) ffffffff8154f344 ipv6_rcv+0x334 ([kernel.kallsyms]) So there is something fundamentally wrong with the use of /proc/kcore. Adrian: I seem to recall you added support for kcore. Any ideas on why the addresses are wrong? David