Re: perf call stacks on 32bit ARM v7

["Wangnan (F)" <wangnan0@huawei.com>]

On 2016/9/28 5:25, Milian Wolff wrote:
> Hello Jean, others.
>
> Can someone please clarify the requirements for getting perf to properly
> unwind the call stack on 32bit ARM v7?
>
> Looking at [1], it seems that I need either (a) frame pointers, or (b) DWARF
> debug information. Because (a) is often not available, and (b) is too large
> for small flash drives on embedded - how do I use perf with split debug
> information files? I.e. I have tries to record on the arm board using DWARF:
>
> arm-v7$ perf record --call-graph dwarf ...
>
> Then transferred the perf.data file over to my host machine. Perf archive said
> that no build-id's could be found, so I'm not using that. Instead, I try to
> ask perf to find the split debug packes using symfs:
>
> x86-64$ perf report --symfs ... -g graph
>
> But that does not work and I'm not seeing any backtraces. Stracing the report,
> I don't see it even trying to access files - how can I debug this and figure
> out what I'm supposed to be using?

Unfortunaetly, currently perf only supports corss decoding dwarf
for x86_64, x86_32 and arm64. ARM32 is not on the list.

Please see:

http://www.spinics.net/lists/kernel/msg2266293.html

and

tools/perf/util/unwind-libunwind.c

I think adding ARM32 support should not be very hard on perf side.
Add He Kuang to the CC list, he is the author of this patch set.

Thank you.