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From: Milian Wolff <milian.wolff@kdab.com>
To: Jiri Olsa <jolsa@redhat.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: Re: PEBS level 2/3 breaks dwarf unwinding! [WAS: Re: Broken dwarf unwinding - wrong stack pointer register value?]
Date: Tue, 06 Nov 2018 21:04:08 +0100	[thread overview]
Message-ID: <2102566.fCj8pZGm78@agathebauer> (raw)
In-Reply-To: <20181106083957.GB8081@krava>

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On Dienstag, 6. November 2018 09:39:57 CET Jiri Olsa wrote:
> On Mon, Nov 05, 2018 at 04:10:37PM -0800, Andi Kleen wrote:
> > > > > - PMU triggers interrupt and PEBS stores RIP etc.
> > > > > - code continous to execute, possibly changing the stack
> > > > 
> > > > I dont think the code continues to execute.. the stack is ok
> > > 
> > > Are you sure about this? I mean, isn't that the whole reason why we need
> > > PEBS? Generally, if you are sure about this, can you point me to some
> > > documentation on this to allow me to understand it better?
> > 
> > Milian is right.
> > 
> > There is a execution window from PEBS capturing registers to actually
> > triggering the PMU, and if there is stack manipulation in that window
> > the PEBS state might be out of sync with the real stack.
> 
> hum, is this about having 'large pebs' or there's this window
> if there's also only single pebs record allowed? which should
> be case for dwarf unwind
> 
> > The right RIP/RSP to use for the stack unwinding is always the data
> > in the PMI's exception frame on the stack.
> > 
> > Probably would need to modify perf to report those too in addition
> > to the PEBS registers.
> 
> ok, should not be that hard

Where would I look for the source to change here? So far, I only concentrated 
on the userspace side of perf in tools/perf.

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

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  parent reply	other threads:[~2018-11-06 20:04 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-20 22:39 Broken dwarf unwinding - wrong stack pointer register value? Milian Wolff
2018-10-21 20:32 ` Milian Wolff
2018-10-22 10:35 ` Milian Wolff
2018-10-22 11:17   ` Milian Wolff
2018-10-22 13:58     ` Andi Kleen
2018-10-22 19:26       ` Milian Wolff
2018-10-23  4:03         ` Andi Kleen
2018-10-23 10:34           ` Milian Wolff
2018-10-24 14:48             ` Andi Kleen
2018-10-30 22:34               ` Milian Wolff
2018-11-01 22:08                 ` PEBS level 2/3 breaks dwarf unwinding! [WAS: Re: Broken dwarf unwinding - wrong stack pointer register value?] Milian Wolff
2018-11-02 11:26                   ` Jiri Olsa
2018-11-02 17:56                     ` Milian Wolff
2018-11-05 20:51                       ` Jiri Olsa
2018-11-05 22:54                         ` Milian Wolff
2018-11-06  0:10                           ` Andi Kleen
2018-11-06  8:39                             ` Jiri Olsa
2018-11-06 17:26                               ` Andi Kleen
2018-11-06 20:04                               ` Milian Wolff [this message]
2018-11-06 20:24                                 ` Andi Kleen
2018-11-07 22:41                                   ` Milian Wolff
2018-11-08 12:41                                     ` Milian Wolff
2018-11-09  0:55                                       ` Andi Kleen
2018-11-09  0:54                                     ` Andi Kleen
2018-11-10 21:42                             ` Travis Downs
2018-11-11  1:07                               ` Andi Kleen
     [not found]                                 ` <CAOBGo4zirLiKX8VcROAE=kAD0+qkF0E-cBv9DtBiQr=_obDv5w@mail.gmail.com>
2018-11-11  2:54                                   ` Travis Downs
2018-11-12  3:26                                   ` Andi Kleen
2018-11-14 13:20                                     ` Milian Wolff
2018-11-15  2:05                                       ` Travis Downs
2018-11-15  9:10                                         ` Milian Wolff
2018-11-15 19:00                                           ` Andi Kleen
2018-11-15  2:15                                     ` Travis Downs

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