From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757306Ab2FYQJV (ORCPT ); Mon, 25 Jun 2012 12:09:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:28735 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754542Ab2FYQJT (ORCPT ); Mon, 25 Jun 2012 12:09:19 -0400 Date: Mon, 25 Jun 2012 18:08:47 +0200 From: Jiri Olsa To: David Ahern Cc: linux-kernel@vger.kernel.org, psuriset@linux.vnet.ibm.com, Arnaldo Carvalho de Melo , Ingo Molnar , Namhyung Kim , Frederic Weisbecker , Peter Zijlstra Subject: Re: [PATCH] perf kvm: fix segfault with default guest arguments Message-ID: <20120625160847.GE30293@krava.brq.redhat.com> References: <1340599286-89757-1-git-send-email-dsahern@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1340599286-89757-1-git-send-email-dsahern@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 24, 2012 at 10:41:26PM -0600, David Ahern wrote: > (This time with actual backtrace; forgot to remove the leading '#' on the frames.) > > File generated with: > $ perf kvm --host --guest --guestkallsyms=/tmp/guest-kallsyms > --guestmodules=/tmp/guest-modules record -a > > The report command: > $ perf kvm --host --guest --guestkallsyms=/tmp/guest-kallsyms > --guestmodules=/tmp/guest-modules report > > dies with a SEGFAULT: > Program received signal SIGSEGV, Segmentation fault. > 0x000000000046dd7b in machine__mmap_name (self=0x0, bf=0x7fffffffbd20 "q\021", size=4096) at util/map.c:715 > 715 snprintf(bf, size, "[%s.%d]", "guest.kernel.kallsyms", self->pid); > > (gdb) bt > 0 0x000000000046dd7b in machine__mmap_name (self=0x0, bf=0x7fffffffbd20 "q\021", size=4096) at util/map.c:715 > 1 0x0000000000444161 in perf_event__process_kernel_mmap (tool=0x7fffffffdd80, event=0x7ffff7fb4120, machine=0x0) at util/event.c:562 > 2 0x0000000000444642 in perf_event__process_mmap (tool=0x7fffffffdd80, event=0x7ffff7fb4120, sample=0x7fffffffd210, machine=0x0) > at util/event.c:668 > 3 0x0000000000470e0b in perf_session_deliver_event (session=0x915ca0, event=0x7ffff7fb4120, sample=0x7fffffffd210, tool=0x7fffffffdd80, > file_offset=8480) at util/session.c:979 > 4 0x000000000047032e in flush_sample_queue (s=0x915ca0, tool=0x7fffffffdd80) at util/session.c:679 > 5 0x0000000000471c8d in __perf_session__process_events (session=0x915ca0, data_offset=400, data_size=150448, file_size=150848, tool= > 0x7fffffffdd80) at util/session.c:1363 > 6 0x0000000000471d42 in perf_session__process_events (self=0x915ca0, tool=0x7fffffffdd80) at util/session.c:1379 > 7 0x000000000042484a in __cmd_report (rep=0x7fffffffdd80) at builtin-report.c:368 > 8 0x0000000000425bf1 in cmd_report (argc=0, argv=0x915b00, prefix=0x0) at builtin-report.c:756 > 9 0x0000000000438505 in __cmd_report (argc=4, argv=0x7fffffffe260) at builtin-kvm.c:84 > 10 0x000000000043882a in cmd_kvm (argc=4, argv=0x7fffffffe260, prefix=0x0) at builtin-kvm.c:131 > 11 0x00000000004152cd in run_builtin (p=0x7a54e8, argc=9, argv=0x7fffffffe260) at perf.c:273 > 12 0x00000000004154c7 in handle_internal_command (argc=9, argv=0x7fffffffe260) at perf.c:345 > 13 0x0000000000415613 in run_argv (argcp=0x7fffffffe14c, argv=0x7fffffffe140) at perf.c:389 > 14 0x0000000000415899 in main (argc=9, argv=0x7fffffffe260) at perf.c:487 > > If no samples hit within a guest module then no build id events are written > to the header during the record. On the report side this cases no 'machine' > to be generated for the default guest (pid == 0) leading to a > machine == NULL in perf_session_deliver_event. > > perf's handling of default kallsyms and guest-modules needs to be reworked. agreed ;) any plans on that? jirka