linux-kernel - Re: [PATCH/RFC 03/16] perf top: Factor out warnings about kernel addresses and symbols

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Date:	Mon, 14 Dec 2015 11:02:55 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Stephane Eranian <eranian@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH/RFC 03/16] perf top: Factor out warnings about kernel
 addresses and symbols

On Mon, Dec 14, 2015 at 10:44 AM, Namhyung Kim <namhyung@...nel.org> wrote:
> Hi Arnaldo,
>
> On Thu, Dec 10, 2015 at 04:07:48PM -0300, Arnaldo Carvalho de Melo wrote:
>> Em Thu, Dec 10, 2015 at 04:53:22PM +0900, Namhyung Kim escreveu:
>> > Factor out warning messages into separate functions.  These will be
>> > called in the display thread later.
>> >
>> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
>> > ---
>> >  tools/perf/builtin-top.c | 95 ++++++++++++++++++++++++++----------------------
>> >  1 file changed, 51 insertions(+), 44 deletions(-)
>>
>> Without applying patch 2, will check if it happens without this patch as well
>>
>>
>>
>> [root@...andy ~]# echo 2 > /proc/sys/kernel/kptr_restrict
>> [root@...andy ~]# perf top
>> perf: Segmentation fault
>> -------- backtrace --------
>> perf[0x538b3b]
>> /lib64/libc.so.6(+0x35650)[0x7f401c036650]
>> perf[0x43af66]
>> perf(cmd_top+0xedf)[0x43cdbf]
>> perf[0x47b7c3]
>> perf(main+0x617)[0x4222b7]
>> /lib64/libc.so.6(__libc_start_main+0xf5)[0x7f401c022af5]
>> perf[0x4223c9]
>> [0x0]
>> [root@...andy ~]#
>
> This patch changed the order in the condition, so if kptr_restrict is
> on, kernel map is NULL and checking al->map->dso caused the segfault.

Oh, it's not this patch.  This patch just move the condition as is but
I did the change in the patch 5/16.  Will fix there.

Thanks,
Namhyung
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