Defintion of CONTEXT

Defintion of CONTEXT

[Domenico Di Leo]

Hello,
in several stp scripts, files .c and .h  appear the variable CONTEXT,
I would like to take at look at its definition,
I guess it is a struct, but where is it defined?
Thank you in  advance,
Domenico

-- 
Domenico Di Leo, PhD student, Università degli Studi di Napoli Federico II
Ph:     +39 081 676770
Fax:    +39 081 676574
Web: http://wpage.unina.it/domenico.dileo (WP)

Re: Defintion of CONTEXT

[Frank Ch. Eigler]

Domenico Di Leo <domenico.dileo@unina.it> writes:

> in several stp scripts, files .c and .h  appear the variable CONTEXT,
> I would like to take at look at its definition,
> I guess it is a struct, but where is it defined?

CONTEXT is a pointer into a "struct context[]" array, which is a place
to store sizeable local variables for the currently running
probe/function.  Such locals are stored on the heap rather than on the
(scarce) kernel stack.

- FChE

Re: Defintion of CONTEXT

[domenico.dileo]

ok, but I would like to find out about the several
information to which is possible to access with CONTEXT.
For instance, CONTEXT->regs allows you to get the
value stored in some registers (I guess),
There are other fields, such as CONTEXT->regflags, CONTEXT->pi
and so on. Where can I find a full description (or definition)
of CONTEXT? What can I access to with CONTEXT?.
Thank you in advance.



Quoting "Frank Ch. Eigler" <fche@redhat.com>:

> Domenico Di Leo <domenico.dileo@unina.it> writes:
>
>> in several stp scripts, files .c and .h  appear the variable CONTEXT,
>> I would like to take at look at its definition,
>> I guess it is a struct, but where is it defined?
>
> CONTEXT is a pointer into a "struct context[]" array, which is a place
> to store sizeable local variables for the currently running
> probe/function.  Such locals are stored on the heap rather than on the
> (scarce) kernel stack.
>
> - FChE
>
>



Domenico Di Leo, PhD student, Universit? degli Studi di Napoli Federico II
Ph:     +39 081 676770
Fax:    +39 081 676574
Web: http://wpage.unina.it/domenico.dileo

Re: Defintion of CONTEXT

[Mark Wielaard]

On Mon, 2012-08-06 at 10:20 +0200, domenico.dileo@unina.it wrote:
> ok, but I would like to find out about the several
> information to which is possible to access with CONTEXT.
> For instance, CONTEXT->regs allows you to get the
> value stored in some registers (I guess),
> There are other fields, such as CONTEXT->regflags, CONTEXT->pi
> and so on. Where can I find a full description (or definition)
> of CONTEXT? What can I access to with CONTEXT?.

It is internal to the systemtap runtime and really not supposed to be
accessed by user code. But if you are interested in the internals then
take a look at runtime/common_probe_context.h which has several comments
describing the fields:
http://www.sourceware.org/git/gitweb.cgi?p=systemtap.git;a=blob;f=runtime/common_probe_context.h;hb=HEAD