linux-kernel - Re: [PATCH 14/18] perf tools: Make vmlinux short name more like kallsyms short name

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Date:	Mon, 10 Nov 2014 15:13:46 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Adrian Hunter <adrian.hunter@...el.com>,
	David Ahern <dsahern@...il.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 14/18] perf tools: Make vmlinux short name more like kallsyms short name

Hi Jiri,

On Sun, 9 Nov 2014 08:51:26 +0100, Jiri Olsa wrote:
> On Thu, Nov 06, 2014 at 06:04:35PM -0300, Arnaldo Carvalho de Melo wrote:
>> From: Namhyung Kim <namhyung@...nel.org>
>> 
>> The previous patch changed kernel dso name from '[kernel.kallsyms]' to
>> vmlinux.  However it might add confusion to old users accustomed to the
>> old name.  So change the short name to '[kernel.vmlinux]' to reduce such
>> confusion.
>> 
>
> SNIP
>
>> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
>> ---
>>  tools/perf/util/machine.c | 3 +++
>>  1 file changed, 3 insertions(+)
>> 
>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>> index 53f90e9c65fe..52e94902afb1 100644
>> --- a/tools/perf/util/machine.c
>> +++ b/tools/perf/util/machine.c
>> @@ -1106,6 +1106,9 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
>>  		if (__machine__create_kernel_maps(machine, kernel) < 0)
>>  			goto out_problem;
>>  
>> +		if (strstr(dso->long_name, "vmlinux"))
>> +			dso__set_short_name(dso, "[kernel.vmlinux]", false);
>> +
>
> heya,
> I've got attached segfault in perf script because of this,
> if I revert it's ok..

Oops, sorry.  It seems somehow to fail to find a matching kernel dso
from the build-id table..  anyway we need to access 'kernel' instead of
'dso' since it might be invalid at this time.

Could you please check below patch?


>From e28ec815465721b81669c47eb00d8307f4b424cd Mon Sep 17 00:00:00 2001
From: Namhyung Kim <namhyung@...nel.org>
Date: Mon, 10 Nov 2014 15:05:26 +0900
Subject: [PATCH] perf tools: Fix segfault due to invalid kernel dso access

When processing kernel mmap event, it should access the 'kernel'
variable as sometimes it cannot find a matching dso from build-id
table so 'dso' might be invalid.

Reported-by: Jiri Olsa <jolsa@...hat.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/machine.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 52e94902afb1..85033d80fd6a 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1106,8 +1106,8 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
 		if (__machine__create_kernel_maps(machine, kernel) < 0)
 			goto out_problem;
 
-		if (strstr(dso->long_name, "vmlinux"))
-			dso__set_short_name(dso, "[kernel.vmlinux]", false);
+		if (strstr(kernel->long_name, "vmlinux"))
+			dso__set_short_name(kernel, "[kernel.vmlinux]", false);
 
 		machine__set_kernel_mmap_len(machine, event);
 
-- 
2.1.2

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