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Date: Mon, 10 Oct 2016 16:59:24 +1100
From: Nicholas Piggin <npiggin@gmail.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Anton Blanchard <anton@samba.org>, Benjamin Herrenschmidt
 <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>,
 ravi.bangoria@linux.vnet.ibm.com, acme@redhat.com, peterz@infradead.org,
 mingo@redhat.com, alexander.shishkin@linux.intel.com,
 linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: perf TUI fails with "failed to process type: 64"
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On Mon, 10 Oct 2016 16:02:07 +1100
Michael Ellerman <mpe@ellerman.id.au> wrote:

> Anton Blanchard <anton@samba.org> writes:
> 
> > Hi,
> >
> > Updating to mainline as of last night, I started seeing the following
> > error when running the perf report TUI:
> >
> > 0x46068 [0x8]: failed to process type: 68
> >
> > This event is just PERF_RECORD_FINISHED_ROUND:
> >
> > 0x46068 [0x8]: event: 68
> > .
> > . ... raw event: size 8 bytes
> > .  0000:  44 00 00 00 00 00 08 00                          D.......        
> >
> > 0x46068 [0x8]: PERF_RECORD_FINISHED_ROUND
> >
> > Which of course is not our error. It took me a while to find the real
> > culprit:
> >
> >  14c00-14c00 g exc_virt_0x4c00_system_call  
>    ^
>    What's this? The address? If so it's wrong?
>    
> 
> > A zero length symbol, which __symbol__inc_addr_samples() barfs on:
> >
> >         if (addr < sym->start || addr >= sym->end) {
> > ...
> > 		return -ERANGE;
> >
> > Seems like we have 3 bugs here:  
> ...
> >
> > 3. Why do we have zero length symbols in the first place? Does the recent
> >    ppc64 exception clean up have something to do with it?  
> 
> Seems likely. But I can't see why.
> 
> AFAICS we have never emitted a size for those symbols:
> 
> Old:
> $ nm --print-size build/vmlinux | grep -w system_call_relon_pSeries
> c000000000004c00 T system_call_relon_pSeries
> 
> New:
> $ nm --print-size build/vmlinux | grep -w exc_virt_0x4c00_system_call
> c000000000004c00 T exc_virt_0x4c00_system_call
> 
> 
> It also doesn't look like we're emitting another symbol with the same
> address, which has caused confusion in the past:
> 
> Old:
> c000000000004c00 T exc_virt_0x4c00_system_call
> c000000000004d00 T exc_virt_0x4d00_single_step
> 
> New:
> c000000000004c00 T system_call_relon_pSeries
> c000000000004d00 T single_step_relon_pSeries
> 
> 
> So more digging required.

Yeah, strange. Maybe perf changes?

We were talking about adding size and type to the exception symbols
though.