updated example scripts

updated example scripts

[Stuart Kendrick]

I have just installed systemtap-2.4 under Precise Pangolin
I compiled using gcc-4.8.1

Linux ubuntu 3.8.0-35-generic #50~precise1-Ubuntu SMP Wed Dec 4
17:25:51 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

Some of the example scripts run:  dropwatch.stp and tcp_connections.stp...

But some do not:  nettop.stp, socktop, tcp_trace.stp ...

The failing ones throw dwarf errors:
./nettop.stp

semantic error: not accessible at this address [man error::dwarf]
(0xffffffff815e6870, dieoffset: 0x54970df): identifier '$skb' at
/usr/local/share/systemtap/
tapset/linux/networking.stp:82:27
        source:         dev_name = kernel_string($skb->dev->name)
                                                 ^
Pass 2: analysis failed.  [man error::pass2]
Number of similar error messages suppressed: 15.
Rerun with -v to see them.

The failing ones throw dwarf errors:
./nettop.stp

semantic error: not accessible at this address [man error::dwarf]
(0xffffffff815e6870, dieoffset: 0x54970df): identifier '$skb' at
/usr/local/share/systemtap/tapset/linux/networking.stp:82:27
        source:         dev_name = kernel_string($skb->dev->name)
                                                 ^
Pass 2: analysis failed.  [man error::pass2]
Number of similar error messages suppressed: 15.
Rerun with -v to see them.

I'm guessing that these scripts are running into the challenges of
finding particular variables:
https://sourceware.org/systemtap/wiki/TipContextVariables"

Has anyone twinked with one or more of the three scripts above in such
a way as to make them more likely to run under 3.8.0-x?

--sk

Stuart Kendrick

Re: updated example scripts

[David Smith]

Sorry for the late reply to this. I meant to respond earlier, but got
sidetracked...

On 01/10/2014 11:26 AM, Stuart Kendrick wrote:
> I have just installed systemtap-2.4 under Precise Pangolin
> I compiled using gcc-4.8.1
> 
> Linux ubuntu 3.8.0-35-generic #50~precise1-Ubuntu SMP Wed Dec 4
> 17:25:51 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> 
> Some of the example scripts run:  dropwatch.stp and tcp_connections.stp...
> 
> But some do not:  nettop.stp, socktop, tcp_trace.stp ...
> 
> The failing ones throw dwarf errors:
> ./nettop.stp
> 
> semantic error: not accessible at this address [man error::dwarf]
> (0xffffffff815e6870, dieoffset: 0x54970df): identifier '$skb' at
> /usr/local/share/systemtap/
> tapset/linux/networking.stp:82:27
>         source:         dev_name = kernel_string($skb->dev->name)
>                                                  ^
> Pass 2: analysis failed.  [man error::pass2]
> Number of similar error messages suppressed: 15.
> Rerun with -v to see them.
> 
> The failing ones throw dwarf errors:
> ./nettop.stp
> 
> semantic error: not accessible at this address [man error::dwarf]
> (0xffffffff815e6870, dieoffset: 0x54970df): identifier '$skb' at
> /usr/local/share/systemtap/tapset/linux/networking.stp:82:27
>         source:         dev_name = kernel_string($skb->dev->name)
>                                                  ^
> Pass 2: analysis failed.  [man error::pass2]
> Number of similar error messages suppressed: 15.
> Rerun with -v to see them.
> 
> I'm guessing that these scripts are running into the challenges of
> finding particular variables:
> https://sourceware.org/systemtap/wiki/TipContextVariables"
> 
> Has anyone twinked with one or more of the three scripts above in such
> a way as to make them more likely to run under 3.8.0-x?

We don't guarantee that all examples run everywhere. Some examples were
written to a specific kernel feature that may not exist in current kernels.

In the case of nettop.stp, it compiles fine for me on
2.6.32-431.3.1.el6.x86_64 and 3.13.0-0.rc8.git4.1.fc21.x86_64. I don't
seem to have a 3.8 kernel lying around.

Your error above isn't coming from nettop.stp exactly, it is coming from
tapset/linux/networking.stp. It is odd that you can't find $skb. Try the
following command:

# stap -L 'kernel.function("dev_queue_xmit")'

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)