Re: Probing symbols that are not EXPORT()ed

Re: Probing symbols that are not EXPORT()ed

[Alan David Brunelle]

> Figured it out - this works.
>
> global rqs
>
> probe module("*scsi_mod*").function("scsi_dispatch_cmd")
> {
>        rqs <<< ($cmd->request_bufflen / 512)
> }
>
> probe end
> {
>        print(@hist_log(rqs))
>        exit()
> } 

Re: Probing symbols that are not EXPORT()ed

[Li Guanglei]

Alan David Brunelle ??:

> global rqs
> 
> probe kernel.function("scsi_dispatch_cmd")
> {
>        rqs <<< $cmd->request_bufflen
> }
> 
> Alan

There is already a probe alias defined in Systemtap for this.

/usr/share/systemtap/tapsets/scsi.stp:

...
/* Dispatch a command to the low-level driver. */
probe scsi.iodispatching
         = module("*").function("scsi_dispatch_cmd@drivers/scsi/scsi.c")
{

         host_no = $cmd->device->host->host_no
         channel = $cmd->device->channel
         lun = $cmd->device->lun
         dev_id = $cmd->device->id
         device_state = $cmd->device->sdev_state
         data_direction = $cmd->sc_data_direction
         request_buffer = $cmd->request_buffer
         req_bufflen = $cmd->request_bufflen
}
...

And this alias also have some predefined variables for you to use.

- Guanglei

Re: Probing symbols that are not EXPORT()ed

[William Cohen]

Alan David Brunelle wrote:
> [Sorry for this newbie question...]
> 
> How does one probe on a kernel function that does not have an
> 
> EXPORT_SYMBOL()
> 
> invocation?
> 
> For example the following fails:
> 
> global rqs
> 
> probe kernel.function("scsi_dispatch_cmd")
> {
>        rqs <<< $cmd->request_bufflen
> }
> 
> probe end
> {
>        print(@hist_linear(rqs, 0, 512000, 4000))
>        exit()
> }
> 
> with:
> 
> [root@bl25p1 06_08]# stap -v scwrite.stp
> Pass 1: parsed user script and 11 library script(s) in 40usr/0sys/51real 
> ms.
> semantic error: no match for probe point
>         while: resolving probe point kernel.function("scsi_dispatch_cmd")
> Pass 2: analyzed script: 1 probe(s), 4 function(s), 1 global(s) in 
> 150usr/20sys/163real ms.
> Pass 2: analysis failed.
> 
> Thanks,
> Alan

Is this in the scsi module?

Shouldn't it be something like:

probe kernel.module("scsi_mod").function("scsi_dispatch_cmd")
{
        rqs <<< $cmd->request_bufflen
}

Re: Probing symbols that are not EXPORT()ed

[Martin Hunt]

On Thu, 2006-06-08 at 13:15 -0400, Alan David Brunelle wrote:
> [Sorry for this newbie question...]
> 
> How does one probe on a kernel function that does not have an
> EXPORT_SYMBOL()

There is no requirement to have functions exported before they can be
probed.

> For example the following fails:
> probe kernel.function("scsi_dispatch_cmd")
> {
>         rqs <<< $cmd->request_bufflen
> }

That function is normally in a module, not in the kernel. So you have to
do either:
probe module("scsi_mod").function("scsi_dispatch_cmd")
OR
probe module("*").function("scsi_dispatch_cmd")

Martin

Probing symbols that are not EXPORT()ed

[Alan David Brunelle]

[Sorry for this newbie question...]

How does one probe on a kernel function that does not have an

EXPORT_SYMBOL()

invocation?

For example the following fails:

global rqs

probe kernel.function("scsi_dispatch_cmd")
{
        rqs <<< $cmd->request_bufflen
}

probe end
{
        print(@hist_linear(rqs, 0, 512000, 4000))
        exit()
}

with:

[root@bl25p1 06_08]# stap -v scwrite.stp
Pass 1: parsed user script and 11 library script(s) in 40usr/0sys/51real ms.
semantic error: no match for probe point
         while: resolving probe point kernel.function("scsi_dispatch_cmd")
Pass 2: analyzed script: 1 probe(s), 4 function(s), 1 global(s) in 
150usr/20sys/163real ms.
Pass 2: analysis failed.

Thanks,
Alan