Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933295Ab2HXWOa (ORCPT ); Fri, 24 Aug 2012 18:14:30 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:58532 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932414Ab2HXWO1 (ORCPT ); Fri, 24 Aug 2012 18:14:27 -0400 Message-ID: <5037FC9F.3090603@fb.com> Date: Fri, 24 Aug 2012 15:13:51 -0700 From: Arun Sharma User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:14.0) Gecko/20120713 Thunderbird/14.0 MIME-Version: 1.0 To: LKML CC: Jiri Olsa , Arnaldo Carvalho de Melo , Benjamin Redelings , Corey Ashford , Cyrill Gorcunov , "Frank Ch. Eigler" , Frederic Weisbecker , Ingo Molnar , Masami Hiramatsu , Paul Mackerras , Peter Zijlstra , Robert Richter , Stephane Eranian , Tom Zanussi , Ulrich Drepper Subject: perf backtraces off-by-1 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.18.254] X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.7.7855,1.0.260,0.0.0000 definitions=2012-08-24_08:2012-08-24,2012-08-24,1970-01-01 signatures=0 X-Proofpoint-Spam-Reason: safe Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1764 Lines: 50 Some of our language runtimes like to map IP addresses in perf backtrace to specific byte codes. The way things stand now, the addresses on the backtrace are return addresses, rather than the caller. I think this issue may be present for other unusual call/return sequences where the user may be more interested in the calling instruction rather than the instruction control flow would return to. A simple hack such as the one below makes our JIT guys happy. But the code is not right if there was an asynchronous transfer of control (eg: signal handler or interrupt). libunwind contains similar code, but has the additional info in the unwind information to recognize async control transfer. Wondering if this has been discussed before. One option is to support this for user mode only, with code to detect signal frames. Any other ideas? -Arun --- a/tools/perf/util/session.c +++ b/tools/perf/util/session.c @@ -296,6 +296,7 @@ int machine__resolve_callchain(struct machine *self, struct perf_evsel *evsel, u8 cpumode = PERF_RECORD_MISC_USER; unsigned int i; int err; + int async; callchain_cursor_reset(&evsel->hists.callchain_cursor); @@ -322,6 +323,11 @@ int machine__resolve_callchain(struct machine *self, struct perf_evsel *evsel, continue; } + /* XXX: check if this was an async control transfer */ + async = 0; + if (!async) { + ip--; + } al.filtered = false; thread__find_addr_location(thread, self, cpumode, MAP__FUNCTION, ip, &al, NULL); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/