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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/