Communication between kernel and kernel module

Communication between kernel and kernel module

[drewd77.gm]

Hi,

Is there any way to call a function defined in a kernel module from within
the kernel proper?

Here's what I'm trying to do:

I'm trying to keep track of when and for how long a process is being
executed on the processor, i.e. I need to know when context switches occur.

There is a function called context_switch() in linux/kernel/sched/core.c
that is called whenever a context switch happens. I would like to call a
function in a kernel module I've written from within context_switch() and
pass some data to it.

I've seen how to communicate between user space and kernel space, such as
using a file in /dev or using system calls, but not how to communicate
within the kernel itself.

Regards,
Drew
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Communication between kernel and kernel module

[Vlad Dogaru]

On Tue, May 22, 2012 at 9:18 PM, drewd77.gm <drewd77.gm@gmail.com> wrote:
> Hi,
>
> Is there any way to call a function defined in a kernel module from within
> the kernel proper?
>
> Here's what I'm trying to do:
>
> I'm trying to keep track of when and for how long a process is being
> executed on the processor, i.e. I need to know when context switches occur.

Kprobes [1] might be useful.  I for one haven't used Kprobes before,
but I'm sure others on this list can provide useful insight.

[1] http://lwn.net/Articles/132196/

Hope this helps,
Vlad

Communication between kernel and kernel module

[刘智猷]

Hi,
On 05/23/2012 02:18 AM, drewd77.gm wrote:
> Hi,
>
> Is there any way to call a function defined in a kernel module from 
> within the kernel proper?
>
> Here's what I'm trying to do:
>
> I'm trying to keep track of when and for how long a process is being 
> executed on the processor, i.e. I need to know when context switches 
> occur.
>
> There is a function called context_switch() 
> in linux/kernel/sched/core.c that is called whenever a context switch 
> happens. I would like to call a function in a kernel module I've 
> written from within context_switch() and pass some data to it.
There are lots of ways to do it, maybe you don't need to write a module 
or hacking the kernel like that... Check perf and systemtap. They may help.
>
> I've seen how to communicate between user space and kernel space, such 
> as using a file in /dev or using system calls, but not how to 
> communicate within the kernel itself.
>
> Regards,
> Drew
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Regards,
LIU Zhiyou
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Communication between kernel and kernel module

[Frank Ch. Eigler]

"drewd77.gm" <drewd77.gm@gmail.com> writes:

> Is there any way to call a function defined in a kernel module from within the
> kernel proper?

One needs a proper hook mechanism such as kprobes or tracepoints.

> I'm trying to keep track of when and for how long a process is being executed
> on the processor, i.e. I need to know when context switches occur.
>
> There is a function called context_switch() in?linux/kernel/sched/core.c that
> is called whenever a context switch happens. I would like to call a function in
> a kernel module I've written from within context_switch() and pass some data to
> it.

The sched_switch tracepoint is probably the best spot for this.  A
systemtap script that listens for these events and simply traces them
to stdout looks like:

probe scheduler.ctxswitch { println(cpu(), ":", prev_tid, "->", next_tid) }

- FChE