From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=Fmhj=NM=vger.kernel.org=linux-kernel-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,
	DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,PLING_QUERY,
	SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id A6B62C0044C
	for <linux-kernel@archiver.kernel.org>; Thu,  1 Nov 2018 22:08:29 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id 5D5E1204FD
	for <linux-kernel@archiver.kernel.org>; Thu,  1 Nov 2018 22:08:29 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=pass (1024-bit key) header.d=kdab.com header.i=@kdab.com header.b="YgBul9Rb"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D5E1204FD
Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=kdab.com
Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1728086AbeKBHNS (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Fri, 2 Nov 2018 03:13:18 -0400
Received: from mail.kdab.com ([176.9.126.58]:18470 "EHLO mail.kdab.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1727638AbeKBHNS (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 2 Nov 2018 03:13:18 -0400
Authentication-Results: mail.kdab.com (amavisd-new); dkim=pass (1024-bit key)
 reason="pass (just generated,
 assumed good)" header.d=kdab.com
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kdab.com; h=
 content-type:content-type:mime-version:references:in-reply-to
 :organization:message-id:date:date:subject:subject:from:from; s=
 dkim; t=1541110102; x=1541974103; bh=8/dmUfKL/9WohGldhTICxy4V4Ud
 6O3h4Ry/FAjT04i0=; b=YgBul9Rbuk6ZdBuNItvvpg7kGrcC7XY4UAbuWBGnNMO
 xBXV1ZLDuVEjV5sOTWpLf0nATiB4UxqABQzWfPeiwBsxNKan+Q9RfiLV6P62b9qw
 21carLBv++gKcU/SpqTDOYqCbbxWGp1pbCUfnMb/LB+5YiNXLxcYD8OCXA5DJsEw
 =
X-Virus-Scanned: amavisd-new at kdab.com
From:   Milian Wolff <milian.wolff@kdab.com>
To:     Milian Wolff <milian.wolff@kdab.com>
Cc:     Andi Kleen <ak@linux.intel.com>, linux-kernel@vger.kernel.org,
        Jiri Olsa <jolsa@kernel.org>, namhyung@kernel.org,
        linux-perf-users@vger.kernel.org,
        Arnaldo Carvalho <acme@kernel.org>
Subject: PEBS level 2/3 breaks dwarf unwinding! [WAS: Re: Broken dwarf
 unwinding - wrong stack pointer register value?]
Date:   Thu, 01 Nov 2018 23:08:18 +0100
Message-ID: <13521319.OzbRBoFVZM@agathebauer>
Organization: KDAB
In-Reply-To: <2122395.LD3O1NFKj8@agathebauer>
References: <2335309.gnWok9HYb4@agathebauer>
 <20181024144818.GF6218@tassilo.jf.intel.com> <2122395.LD3O1NFKj8@agathebauer>
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="nextPart2198123.MMhLtkTpF4";
 micalg="sha256"; protocol="application/pkcs7-signature"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

--nextPart2198123.MMhLtkTpF4
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"

On Dienstag, 30. Oktober 2018 23:34:35 CET Milian Wolff wrote:
> On Mittwoch, 24. Oktober 2018 16:48:18 CET Andi Kleen wrote:
> > > Can someone at least confirm whether unwinding from a function prologue
> > > via
> > > .eh_frame (but without .debug_frame) should actually be possible?
> > 
> > Yes it should be possible. Asynchronous unwind tables should work
> > from any instruction.

<snip>

> We can find `7f91345bdaf8+1 = 7f91345bdaf9" at offset 16 (search for "f9 da
> 5b 34 91 7f"). Using that address makes unwinding work for this sample.
> What could be the reason for this shift?

I believe I have found the culprit: PEBS seems to be at fault here - i.e. the 
RIP/RSP and the ustack dump of the sample simply don't fit together.

Check this out:

```
$ for i in $(seq 10); do perf record -q -e "cycles:" --call-graph dwarf ./cpp-
inlining > /dev/null; perf script | pcre2grep -c -M "hypot_finite.*\n.*\
[unknown\]"; done
0
0
0
0
0
0
0
0
0
0

$ for i in $(seq 10); do perf record -q -e "cycles:p" --call-graph dwarf ./
cpp-inlining > /dev/null; perf script | pcre2grep -c -M "hypot_finite.*\n.*\
[unknown\]"; done
0
0
0
0
0
0
0
0
0
0

$ for i in $(seq 10); do perf record -q -e "cycles:pp" --call-graph dwarf ./
cpp-inlining > /dev/null; perf script | pcre2grep -c -M "hypot_finite.*\n.*\
[unknown\]"; done
37
39
35
28
40
39
29
37
31
26

$ for i in $(seq 10); do perf record -q -e "cycles:ppp" --call-graph dwarf ./
cpp-inlining > /dev/null; perf script | pcre2grep -c -M "hypot_finite.*\n.*\
[unknown\]"; done
79
70
76
77
70
90
64
78
86
74
```

Note how precise levels 0 and 1 do not produce any samples where unwinding 
fails. But precise level 2 produces some, and precise level 3 increases the 
amount (by ca. ~2x).

I can reproduce this pattern on two separate Intel CPUs and kernel versions 
currently:

Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz with 4.18.16-arch1-1-ARCH
Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz with 4.14.78-1-lts

Could someone else try this? What about AMD and IBS - is it also affected? 
What about newer/different Intel CPUs?

Better yet, can someone come up with a fix for this on Intel with maximum 
precise level?

Thanks

-- 
Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt, C++ and OpenGL Experts
--nextPart2198123.MMhLtkTpF4
Content-Type: application/pkcs7-signature; name="smime.p7s"
Content-Disposition: attachment; filename="smime.p7s"
Content-Transfer-Encoding: base64
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--nextPart2198123.MMhLtkTpF4--