[linux-yocto] utrace in recent linux-yocto kernels

[Bruce Ashfield]

On 12-09-10 5:00 PM, Wade Farnsworth wrote:
> Bruce Ashfield wrote:
>> On 12-08-29 09:29 AM, Tom Zanussi wrote:
>>> On Fri, 2012-08-03 at 13:37 -0400, Bruce Ashfield wrote:
>>>> On 12-08-03 12:24 PM, Wade Farnsworth wrote:
>>>>> Hi all,
>>>>>
>>>>> While looking through the linux-yocto repositories, I notice that
>>>>> while
>>>>> linux-yocto-3.0 has the utrace patchset merged, it appears that 3.2
>>>>> and
>>>>> 3.4 do not. utrace is necessary for proper systemtap userspace probe
>>>>> support on these kernel versions, so it would be nice to have it
>>>>> available.
>>>>>
>>>>> Is there any intention to include this series in 3.2 and later
>>>>> kernels?
>>>>
>>>> There is! utrace is largely upstream in 3.5, and a backport is already
>>>> done to 3.4, but pending some work to re-enable systemtap functionality
>>>> on top of it.
>>>>
>>>
>>> Hi Bruce,
>>>
>>> Any ETA on this? - I'd like to try it out. Let me know if you need any
>>> help on anything here...
>>
>> I pushed the majority of it a while back, and systemtap works against it
>> (the latest system tap that is).
>>
>> We could of course have missed something, but see these series:
>>
>> http://git.yoctoproject.org/cgit/cgit.cgi/yocto-kernel-cache/tree/features/uprobe
>>
>>
>>
>> and the in-tree version:
>>
>> http://git.yoctoproject.org/cgit/cgit.cgi/linux-yocto-3.4/commit/?h=standard/base&id=544d531a337d560bd89f44ec45b0f6f2658c8e7c
>>
>>
>>
>> (and down, that's the top commit)
>>
>
> Hi Bruce,
>
> Sorry for the delay in replying. It appears that this patch only
> addresses the recently added inode-based uprobe solution, not the old
> utrace patchset that is present in linux-yocto-3.0.
>
> Recent systemtap versions contain a utrace-based uprobes solution (built
> as an external kernel module) for ARM, but it hasn't been ported over to
> the newer inode-based uprobes solution that is implemented in the
> upstream kernel. It would be nice to carry over the utrace patchset for
> the time being so that ARM users of newer kernels can use at least some
> sort of uprobes solution until the newer solution can be merged
> upstream. Would it be possible to carry both the utrace and uprobes
> patches in the mean time?

We dropped the old ones on purpose, since systemtap is updating to the
new series. The old series was significantly more difficult to port
forward, so I elected to move everything forward to the new uprobes and
wait for the outlying arches to be updated.

Since yocto 1.3 is closed for features, and when we move to yocto 1.4,
chances are we won't spend any dev cycles trying to carry the old and
new patches in the same tree.

But if anyone has a prototype series, I'd be happy to have a look at it :)
I just can't say when (if) time will allow for the patches to be ported
since we are chasing the new mainline implementation as the preference.

Cheers,

Bruce

>
> Thanks for looking into this.
>
> Regards,
>
> Wade Farnsworth