perf TUI fails with "failed to process type: 64"

[Michael Ellerman]

Anton Blanchard <anton at 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.

cheers