linux-kernel - [tip:perf/urgent] perf kvm: Finding struct machine fails for PERF_RECORD

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Date:	Fri, 13 Apr 2012 11:13:18 -0700
From:	"tip-bot for Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, linux-kernel@...r.kernel.org, eranian@...gle.com,
	paulus@...ba.org, mingo@...hat.com, hpa@...or.com,
	mingo@...nel.org, a.p.zijlstra@...llo.nl,
	nikunj@...ux.vnet.ibm.com, fweisbec@...il.com, dsahern@...il.com,
	tglx@...utronix.de
Subject: [tip:perf/urgent] perf kvm:
  Finding struct machine fails for PERF_RECORD_MMAP

Commit-ID:  7fb0a5ee8889488f7568ffddffeb66ddeb50917e
Gitweb:     http://git.kernel.org/tip/7fb0a5ee8889488f7568ffddffeb66ddeb50917e
Author:     Nikunj A. Dadhania <nikunj@...ux.vnet.ibm.com>
AuthorDate: Mon, 9 Apr 2012 13:52:23 +0530
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Wed, 11 Apr 2012 11:45:12 -0300

perf kvm: Finding struct machine fails for PERF_RECORD_MMAP

Running 'perf kvm --host --guest --guestmount /tmp/guestmount record -a -g -- sleep 2'

Was resulting in a segfault. For event type PERF_RECORD_MMAP,
event->ip.pid is being used in perf_session__find_machine_for_cpumode,
which is not correct.

The event->ip.pid field happens to be 0 in this case and results in
returning a NULL machine object. Finally, access to self->pid in
machine__mmap_name, results in a segfault later.

For PERF_RECORD_MMAP type, pass event->mmap.pid.

Signed-off-by: Nikunj A. Dadhania <nikunj@...ux.vnet.ibm.com>
Reviewed-by: David Ahern <dsahern@...il.com>
Tested-by: David Ahern <dsahern@...il.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Nikunj A. Dadhania <nikunj@...ux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120409081835.10576.22018.stgit@abhimanyu.in.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/session.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 9412e3b..00923cd 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -826,8 +826,16 @@ static struct machine *
 {
 	const u8 cpumode = event->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;
 
-	if (cpumode == PERF_RECORD_MISC_GUEST_KERNEL && perf_guest)
-		return perf_session__find_machine(session, event->ip.pid);
+	if (cpumode == PERF_RECORD_MISC_GUEST_KERNEL && perf_guest) {
+		u32 pid;
+
+		if (event->header.type == PERF_RECORD_MMAP)
+			pid = event->mmap.pid;
+		else
+			pid = event->ip.pid;
+
+		return perf_session__find_machine(session, pid);
+	}
 
 	return perf_session__find_host_machine(session);
 }
--
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