linux-kernel - Re: [PATCH] perf report: Fix segfault with '-F phys

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Message-ID: <20191112141801.GA10207@kernel.org>
Date:   Tue, 12 Nov 2019 11:18:01 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        jolsa@...hat.com, kan.liang@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf report: Fix segfault with '-F phys_daddr'

Em Tue, Nov 12, 2019 at 07:28:06PM +0530, Ravi Bangoria escreveu:
> 
> 
> On 11/12/19 4:34 PM, Arnaldo Carvalho de Melo wrote:
> > Em Tue, Nov 12, 2019 at 11:19:46AM +0530, Ravi Bangoria escreveu:
> > > If perf.data file is not recorded with mem-info, adding 'phys_daddr'
> > > to output field in perf report results in segfault. Fix that.
> > > 
> > > Before:
> > >    $ ./perf record ls
> > >    $ ./perf report -F +phys_daddr
> > >    Segmentation fault (core dumped)
> > > 
> > > After:
> > >    $ ./perf report -F +phys_daddr
> > >    Samples: 11  of event 'cycles:u', Event count (approx.): 1485821
> > >    Overhead  Data Physical Address  Command  Shared Object  Symbol
> > >      22.57%  [.] 0000000000000000   ls       libc-2.29.so   [.] __strcoll_l
> > >      21.87%  [.] 0000000000000000   ls       ld-2.29.so     [.] _dl_relocate_object
> > >      ...
> > 
> > Shouldn't we instead just bail out and state that this isn't possible
> > and leave the user wondering why what was asked isn't presented?
> 
> You mean popup with something like "phys_daddr is not available in perf.data"
> and also don't show that column in perf report?

Just bail out completely, something like:


   $ ./perf report -F +phys_daddr
   "phys_daddr" is not available in perf.data, use 'record -e some,thing' to have it.

- Arnaldo