Command line arg for kernel Tracepoints

Command line arg for kernel Tracepoints

[h patel]

Hi,

I am using kernel tracepoints with systemtap scripts.
My requirement is to enable disable certain traces out of these
defined tracepoints in kernel modules.

I tried to pass argument to script but it didn't work, looks like
kernel.trace don't accept command line argument.
Is it true ?

If yes, then i have to write multiple scripts for diff events. Any
other suggestion ?

Thanks,
hp

parse error: command line argument index 1 out of range [1-0]
        at: junk '@1' at test.stp:16:20
     source: probe kernel.trace(@1) { printf("%s
called\n",kernel_string($log)) }

Re: Command line arg for kernel Tracepoints

[Adrien Kunysz]

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On Thu, Dec 30, 2010 at 01:55:26PM +0530, h patel wrote:
> parse error: command line argument index 1 out of range [1-0]

This means @1 and $1 don't exist as no argument was passed to the script
and I doubt this has anything to do with .trace itself. How did you run
the script?

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Re: Command line arg for kernel Tracepoints

[h patel]

Sorry, forgot to reply all.

Hi,

It didn't work. Script can take the argument but kernel.trace can not.
Looks like kernel.trace only handles pattern, not argument.
In that case, I will limit down the types of events.

Thanks,
hp

Error :
parse error: expected literal string or number
       saw: identifier 'tpoint' at test.stp:9:20
    source: probe kernel.trace(tpoint) { printf("%s
called\n",kernel_string($log)) }

On Thu, Dec 30, 2010 at 3:08 PM, Adrien Kunysz <adrien@kunysz.be> wrote:
> I don't think that will ever work like that as @1 and $1 are expanded at
> compile time (I think). You probably need to use a named global variable
> as described in the "ARGUMENTS" section of staprun(8).
>
>        global tpoint = "whateverDefaultProbeYouLike"
>        probe kernel.trace(tpoint) { printf("oh hai\n") }
>
> # stap -m test test.stp
> # staprun test.ko tpoint="anotherTracepoint"
>
> I haven't verified this will work.
>
> On Thu, Dec 30, 2010 at 02:59:58PM +0530, h patel wrote:
>> It's cross compile :
>> host> stap -gv -r /linux-2.6.32.10 -I /target/share/systemtap/tapset
>> -R /target/share/systemtap/runtime -m test test.stp -v
>>
>> host> cat test.stp
>>
>> #! /usr/bin/env stap
>>
>> # Note when we turn the monitor on and off
>> probe begin { printf("Monitoring for wncreg\n") }
>> probe end { printf("Stopping monitor\n") }
>>
>> probe kernel.trace(@1) { printf("%s called\n",kernel_string($log)) }
>>
>>
>>
>>
>> On Thu, Dec 30, 2010 at 2:52 PM, Adrien Kunysz <adrien@kunysz.be> wrote:
>> > On Thu, Dec 30, 2010 at 01:55:26PM +0530, h patel wrote:
>> >> parse error: command line argument index 1 out of range [1-0]
>> >
>> > This means @1 and $1 don't exist as no argument was passed to the script
>> > and I doubt this has anything to do with .trace itself. How did you run
>> > the script?
>> >
>> > -----BEGIN PGP SIGNATURE-----
>> > Version: GnuPG v1.4.9 (GNU/Linux)
>> >
>> > iEYEARECAAYFAk0cT2sACgkQKLX03ZSPZGxRBgCeL/KX+tOJDvgXDy/qz9jR4a+U
>> > uNYAoJszrKWPVm2B3a9n56oavpo7gcR3
>> > =NCSz
>> > -----END PGP SIGNATURE-----
>> >
>> >
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.9 (GNU/Linux)
>
> iEYEARECAAYFAk0cUzIACgkQKLX03ZSPZGwuMQCgisjEWsv6UfkD48ws/TdFt/qL
> 0moAniM28a+br6l+vU245Rjb2czhtTwv
> =PkyI
> -----END PGP SIGNATURE-----
>
>

Re: Command line arg for kernel Tracepoints

[Mark Wielaard]

On Mon, 2011-01-03 at 17:39 +0530, h patel wrote:
> It didn't work. Script can take the argument but kernel.trace can not.
> Looks like kernel.trace only handles pattern, not argument.
> In that case, I will limit down the types of events.
>
> Error :
> parse error: expected literal string or number
>        saw: identifier 'tpoint' at test.stp:9:20
>     source: probe kernel.trace(tpoint) { printf("%s
> called\n",kernel_string($log)) }

Note that kernel.trace() takes a string.
So it would be kernel.trace("tpoint") in your case.
To use wildcards, embed * inside the string.
For example to get a list of all kernel trace points:
stap -l 'kernel.trace("*")'

Cheers,

Mark

Re: Command line arg for kernel Tracepoints

[h patel]

Hi Mark,

tpoint is the global variable.  I want to enable disable tracepoints
at runtime.
Adrien suggested following way :

 global tpoint = "whateverDefaultProbeYouLike"
probe kernel.trace(tpoint) { printf("oh hai\n") }

# stap -m test test.stp
# staprun test.ko tpoint="anotherTracepoint"

I tried kernel.trace(tpoint), kernel.trace($tpoint),
kernel.trace("tpoint"), none of them worked.

Regards,
hp


On Mon, Jan 3, 2011 at 6:14 PM, Mark Wielaard <mjw@redhat.com> wrote:
> On Mon, 2011-01-03 at 17:39 +0530, h patel wrote:
>> It didn't work. Script can take the argument but kernel.trace can not.
>> Looks like kernel.trace only handles pattern, not argument.
>> In that case, I will limit down the types of events.
>>
>> Error :
>> parse error: expected literal string or number
>>        saw: identifier 'tpoint' at test.stp:9:20
>>     source: probe kernel.trace(tpoint) { printf("%s
>> called\n",kernel_string($log)) }
>
> Note that kernel.trace() takes a string.
> So it would be kernel.trace("tpoint") in your case.
> To use wildcards, embed * inside the string.
> For example to get a list of all kernel trace points:
> stap -l 'kernel.trace("*")'
>
> Cheers,
>
> Mark
>
>

Re: Command line arg for kernel Tracepoints

[Mark Wielaard]

On Mon, 2011-01-03 at 20:02 +0530, h patel wrote:
> Hi Mark,
> 
> tpoint is the global variable.  I want to enable disable tracepoints
> at runtime.
> Adrien suggested following way :
> 
>  global tpoint = "whateverDefaultProbeYouLike"
> probe kernel.trace(tpoint) { printf("oh hai\n") }
> 
> # stap -m test test.stp
> # staprun test.ko tpoint="anotherTracepoint"
> 
> I tried kernel.trace(tpoint), kernel.trace($tpoint),
> kernel.trace("tpoint"), none of them worked.

Aha. Sorry, I had misunderstood what you were trying to do. Apologies.

Something like the following should work for that use case:
$ stap -e 'probe kernel.trace(@1) { log(pp()); exit();}' "sys_enter"
kernel.trace("sys_enter")
$ stap -e 'probe kernel.trace(@1) { log(pp()); exit();}' "timer_start"
kernel.trace("timer_start")

Cheers,

Mark

Re: Command line arg for kernel Tracepoints

[Mark Wielaard]

On Mon, 2011-01-03 at 15:39 +0100, Mark Wielaard wrote:
> On Mon, 2011-01-03 at 20:02 +0530, h patel wrote:
> > tpoint is the global variable.  I want to enable disable tracepoints
> > at runtime.
> > Adrien suggested following way :
> > 
> >  global tpoint = "whateverDefaultProbeYouLike"
> > probe kernel.trace(tpoint) { printf("oh hai\n") }
> > 
> > # stap -m test test.stp
> > # staprun test.ko tpoint="anotherTracepoint"
> > 
> > I tried kernel.trace(tpoint), kernel.trace($tpoint),
> > kernel.trace("tpoint"), none of them worked.
> 
> Aha. Sorry, I had misunderstood what you were trying to do. Apologies.
> 
> Something like the following should work for that use case:
> $ stap -e 'probe kernel.trace(@1) { log(pp()); exit();}' "sys_enter"
> kernel.trace("sys_enter")
> $ stap -e 'probe kernel.trace(@1) { log(pp()); exit();}' "timer_start"
> kernel.trace("timer_start")

Actually, I see I am missing the point again.
That would compile in the trace point string.
So you cannot change it at staprun time.

I believe there is indeed no way to change the actual probe at staprun
time at the moment.

Sorry,

Mark