linux-kernel - Re: [PATCH 05/15 V3] perf, c2c: Rework setup code to prepare for features

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Date:	Wed, 09 Apr 2014 10:12:32 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Jiri Olsa <jolsa@...hat.com>, acme@...stprotocols.net,
	LKML <linux-kernel@...r.kernel.org>, jmario@...hat.com,
	fowles@...each.com, peterz@...radead.org, eranian@...gle.com,
	andi.kleen@...el.com
Subject: Re: [PATCH 05/15 V3] perf, c2c: Rework setup code to prepare for features

On Tue, 8 Apr 2014 10:11:07 -0400, Don Zickus wrote:
> On Tue, Apr 08, 2014 at 04:41:29PM +0900, Namhyung Kim wrote:
>> On Sat, 29 Mar 2014 18:10:18 +0100, Jiri Olsa wrote:
>> > On Mon, Mar 24, 2014 at 03:36:56PM -0400, Don Zickus wrote:
>> >
>> > SNIP
>> >
>> >>  
>> >>  static int perf_c2c__process_load_store(struct perf_c2c *c2c,
>> >> +					struct addr_location *al,
>> >>  					struct perf_sample *sample,
>> >> -					struct addr_location *al)
>> >> +					struct perf_evsel *evsel)
>> >>  {
>> >> -	if (c2c->raw_records)
>> >> -		perf_sample__fprintf(sample, ' ', "raw input", al, stdout);
>> >> +	struct mem_info *mi;
>> >> +
>> >> +	mi = sample__resolve_mem(sample, al);
>> >> +	if (!mi)
>> >> +		return -ENOMEM;
>> >
>> > perhaps not directly related to this patchset, but I needed
>> > attached patch to get resolved data in .bss (static), which
>> > for some reason happened to be located in executable segment
>> 
>> Wasn't it a read-only/const data?
>
> I believe it had the 'x' bit set.  Or the kernel was not passing any
> protection bits, so it defaulted to MAP_FUNCTION?

The perf treats a mapping as a data mapping (MAP_VARIABLE) by default if
the 'x' bit is not set.  As Jiri said its a static data, I guessed it's
a const data (set to 0?) and moved into .rodata section and then to the
text segment.

Thanks,
Namhyung
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