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 10:44:05 +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

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.

Will fix.

Thanks,
Namhyung
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