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=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,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 ED85AC04AB9 for ; Wed, 15 Aug 2018 15:07:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E720A214AB for ; Wed, 15 Aug 2018 15:07:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="s9KGwhxL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E720A214AB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729558AbeHOR7h (ORCPT ); Wed, 15 Aug 2018 13:59:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:49506 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729329AbeHOR7g (ORCPT ); Wed, 15 Aug 2018 13:59:36 -0400 Received: from jouet.infradead.org (unknown [179.97.41.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 60EAF214AB; Wed, 15 Aug 2018 15:07:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1534345622; bh=aeydPS9VWIyr7BqEPHk07/OIotxkO2VWU+ODgdo2UYY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=s9KGwhxL0qqFW7VJpD5JZG46jZlnf0aCgg1Rh96M2FCMfDCJNlKdch2dOKs1uWRJq PsrwOM1c49sLpImWgajaNKV09D736NjjMjEKPjicFo8xHhJvjVIw/aemPNvxJuCdWs xFG+/gVC8l7Fx0W0M7Uz6Jhm87022n2De6m1iBJw= From: Arnaldo Carvalho de Melo To: Ingo Molnar Cc: Clark Williams , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Sandipan Das , Aneesh Kumar , Jiri Olsa , Ravi Bangoria , Arnaldo Carvalho de Melo Subject: [PATCH 01/35] perf probe powerpc: Fix trace event post-processing Date: Wed, 15 Aug 2018 12:05:37 -0300 Message-Id: <20180815150611.32080-2-acme@kernel.org> X-Mailer: git-send-email 2.14.4 In-Reply-To: <20180815150611.32080-1-acme@kernel.org> References: <20180815150611.32080-1-acme@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sandipan Das In some cases, a symbol may have multiple aliases. Attempting to add an entry probe for such symbols results in a probe being added at an incorrect location while it fails altogether for return probes. This is only applicable for binaries with debug information. During the arch-dependent post-processing, the offset from the start of the symbol at which the probe is to be attached is determined and added to the start address of the symbol to get the probe's location. In case there are multiple aliases, this offset gets added multiple times for each alias of the symbol and we end up with an incorrect probe location. This can be verified on a powerpc64le system as shown below. $ nm /lib/modules/$(uname -r)/build/vmlinux | grep "sys_open$" ... c000000000414290 T __se_sys_open c000000000414290 T sys_open $ objdump -d /lib/modules/$(uname -r)/build/vmlinux | grep -A 10 "<__se_sys_open>:" c000000000414290 <__se_sys_open>: c000000000414290: 19 01 4c 3c addis r2,r12,281 c000000000414294: 70 c4 42 38 addi r2,r2,-15248 c000000000414298: a6 02 08 7c mflr r0 c00000000041429c: e8 ff a1 fb std r29,-24(r1) c0000000004142a0: f0 ff c1 fb std r30,-16(r1) c0000000004142a4: f8 ff e1 fb std r31,-8(r1) c0000000004142a8: 10 00 01 f8 std r0,16(r1) c0000000004142ac: c1 ff 21 f8 stdu r1,-64(r1) c0000000004142b0: 78 23 9f 7c mr r31,r4 c0000000004142b4: 78 1b 7e 7c mr r30,r3 For both the entry probe and the return probe, the probe location should be _text+4276888 (0xc000000000414298). Since another alias exists for 'sys_open', the post-processing code will end up adding the offset (8 for powerpc64le) twice and perf will attempt to add the probe at _text+4276896 (0xc0000000004142a0) instead. Before: # perf probe -v -a sys_open probe-definition(0): sys_open symbol:sys_open file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /lib/modules/4.18.0-rc8+/build/vmlinux for symbols Open Debuginfo file: /lib/modules/4.18.0-rc8+/build/vmlinux Try to find probe point from debuginfo. Symbol sys_open address found : c000000000414290 Matched function: __se_sys_open [2ad03a0] Probe point found: __se_sys_open+0 Found 1 probe_trace_events. Opening /sys/kernel/debug/tracing/kprobe_events write=1 Writing event: p:probe/sys_open _text+4276896 Added new event: probe:sys_open (on sys_open) ... # perf probe -v -a sys_open%return $retval probe-definition(0): sys_open%return symbol:sys_open file:(null) line:0 offset:0 return:1 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /lib/modules/4.18.0-rc8+/build/vmlinux for symbols Open Debuginfo file: /lib/modules/4.18.0-rc8+/build/vmlinux Try to find probe point from debuginfo. Symbol sys_open address found : c000000000414290 Matched function: __se_sys_open [2ad03a0] Probe point found: __se_sys_open+0 Found 1 probe_trace_events. Opening /sys/kernel/debug/tracing/README write=0 Opening /sys/kernel/debug/tracing/kprobe_events write=1 Parsing probe_events: p:probe/sys_open _text+4276896 Group:probe Event:sys_open probe:p Writing event: r:probe/sys_open__return _text+4276896 Failed to write event: Invalid argument Error: Failed to add events. Reason: Invalid argument (Code: -22) After: # perf probe -v -a sys_open probe-definition(0): sys_open symbol:sys_open file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /lib/modules/4.18.0-rc8+/build/vmlinux for symbols Open Debuginfo file: /lib/modules/4.18.0-rc8+/build/vmlinux Try to find probe point from debuginfo. Symbol sys_open address found : c000000000414290 Matched function: __se_sys_open [2ad03a0] Probe point found: __se_sys_open+0 Found 1 probe_trace_events. Opening /sys/kernel/debug/tracing/kprobe_events write=1 Writing event: p:probe/sys_open _text+4276888 Added new event: probe:sys_open (on sys_open) ... # perf probe -v -a sys_open%return $retval probe-definition(0): sys_open%return symbol:sys_open file:(null) line:0 offset:0 return:1 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /lib/modules/4.18.0-rc8+/build/vmlinux for symbols Open Debuginfo file: /lib/modules/4.18.0-rc8+/build/vmlinux Try to find probe point from debuginfo. Symbol sys_open address found : c000000000414290 Matched function: __se_sys_open [2ad03a0] Probe point found: __se_sys_open+0 Found 1 probe_trace_events. Opening /sys/kernel/debug/tracing/README write=0 Opening /sys/kernel/debug/tracing/kprobe_events write=1 Parsing probe_events: p:probe/sys_open _text+4276888 Group:probe Event:sys_open probe:p Writing event: r:probe/sys_open__return _text+4276888 Added new event: probe:sys_open__return (on sys_open%return) ... Reported-by: Aneesh Kumar Signed-off-by: Sandipan Das Acked-by: Naveen N. Rao Cc: Aneesh Kumar Cc: Jiri Olsa Cc: Ravi Bangoria Fixes: 99e608b5954c ("perf probe ppc64le: Fix probe location when using DWARF") Link: http://lkml.kernel.org/r/20180809161929.35058-1-sandipan@linux.ibm.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/arch/powerpc/util/sym-handling.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c index 53d83d7e6a09..20e7d74d86cd 100644 --- a/tools/perf/arch/powerpc/util/sym-handling.c +++ b/tools/perf/arch/powerpc/util/sym-handling.c @@ -141,8 +141,10 @@ void arch__post_process_probe_trace_events(struct perf_probe_event *pev, for (i = 0; i < ntevs; i++) { tev = &pev->tevs[i]; map__for_each_symbol(map, sym, tmp) { - if (map->unmap_ip(map, sym->start) == tev->point.address) + if (map->unmap_ip(map, sym->start) == tev->point.address) { arch__fix_tev_from_maps(pev, tev, map, sym); + break; + } } } } -- 2.14.4