linux-kernel - [BUG] perf tools: does not process data mmaps correctly

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Message-ID: <CABPqkBSRj4FAQpG_vGOmKzvsv+7oWmtAaesJ5+-RuUJmOer2zw@mail.gmail.com>
Date:	Tue, 30 Oct 2012 21:29:16 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>
Subject: [BUG] perf tools: does not process data mmaps correctly

Arnaldo,

A long time ago, I brought up the issue of perf failing to resolve
data symbols despite having the MAP__VARIABLE map type.

Now that I have posted the PEBS-LL patch series, there is a test
case to debug this.

I looked again at it today. Start from ip__resolve_data() in my patchset.
IT is looking for a data symbol given an address.

Seems to me the core of the problem is how perf processes the MMAP
records in machine__process_mmap_event():

int machine__process_mmap_event(struct machine *machine, union
perf_event *event)
{
      ...

        thread = machine__findnew_thread(machine, event->mmap.pid);
        if (thread == NULL)
                goto out_problem;
        map = map__new(&machine->user_dsos, event->mmap.start,
                        event->mmap.len, event->mmap.pgoff,
                        event->mmap.pid, event->mmap.filename,
                        MAP__FUNCTION);

I don't see any effort to distinguish code from data here. All mmaps are
treated as code.

That could be fine, if then you drop MAP__VARIABLE.

So how is this supposed to work?

Thanks.
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