Re: Re: Regarding systemtap support for AArch64

[Sandeepa Prabhu <sandeepa dot prabhu at linaro dot org>]

On 30 September 2013 08:06, Masami Hiramatsu
<masami.hiramatsu.pt@hitachi.com> wrote:
> (2013/09/26 12:13), Sandeepa Prabhu wrote:
>> Hi Will, Masami,
>>
>> Nice to hear from you, I am using ARM fast model/Foundation model with
>> ARM v8 upstream kernel and a Linaro minimal busybox based ramdisk,
>> testing with loadable modules for now (so don't have dependency on
>> elfutils or GCC autoconf etc)
>>
>> Would you be interested to use Linaro kprobe work as a base for
>> development and validation of systemtap-aarch64?  We are happy to
>> share a public git repo where 'upstream' kernel can be built with
>> kprobes support, which systemtap team can use for verification.  I can
>> do this soon as I have most things working locally, except for
>> kretprobes and 'boosting' support(systemtap can be run without these I
>> believe).
>
> Of course I'm interested in that. Actually I've tried to boot up Linaro's
> Aarch64 kernel on a simulator which ARM is distributing.
> As far as I could see (at that time), aarch64 branch already has singlestep
> implementation for debugging, but no primitive kprobes. And we need to know
> the aarch64 ISA for decoding the binary to find the instructions which will
> be affected by the out-of-line execution, like relative jump, call etc.
Hi Masami,

I am almost done with my first set, will upload and expose my
development branch in couple of days (on linaro public git server) and
then share the info, alongside publishing RFC/RFT on mailing lists.
As for v8 ISA, the public version of ARM ARM is out couple of weeks
back, on silver arm:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0487a/index.html.
 [Although, have developed basic support for handling out-of-line
single stepping as well as simulating literal access & branch, there
are few instructions types that are not supported in kprobes right
now, like exclusive monito, FP/AdvSIMD load/store from symbolic
litreals]

As long as if interested in using sample loadable modules for running,
you would only need a busybox setup, but for systemtap or other tools,
you need a more appropriate file system like fc19 or a open-embedded.

Cheers!
Sandeepa

>
>> Looking forward for a collaboration :-)
>
> Me too ;)
>
> Thanks!
> --
> Masami HIRAMATSU
> IT Management Research Dept. Linux Technology Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: masami.hiramatsu.pt@hitachi.com
>
>