DTrace and CTF data

[Artem Belevich]

You may be confusing CTF info and the probes. Those are different things.

CTF info just describes data types and variable/function location.
DTrace later uses it to figure out where and how to install the
probes.

Probes are installed dynamically, at runtime when DTrace program is
run. That's why you see it with kgdb on the live kernel once probe has
been installed.
DTrace does not modify your original kernel binary, so you will not
see any probes there.

--Artem



On Sun, May 30, 2010 at 12:10 PM, Shrikanth Kamath
<shrikanth07 at gmail.com> wrote:
> I have a query about the FBT provider in DTrace, does FBT provider not need
> the CTF info for the /kernel binary...
>
> I have this observation, when I disassemble say a 'kernel_funtion' , I see
> the function is not instrumented...
>
> (kgdb) disassemble kernel_function
> Dump of assembler code for function kernel_function:
> 0xc04aa05d <kernel_function+0>: push   %ebp
> 0xc04aa05e <kernel_function+1>: mov    %esp,%ebp
> 0xc04aa060 <kernel_function+3>: sub    $0x2c,%esp
>
>
> Now after I did a 'fbt::kernel_function:entry', if I disassemble the
> 'kernel_function'...
>
> (kgdb) disassemble kernel_function
> Dump of assembler code for function kernel_function:
> 0xc04aa05d <kernel_function+0>: lock mov %esp,%ebp                 <== FBT
> instrumentation
> 0xc04aa060 <kernel_function+3>: sub    $0x2c,%esp
>
> If I do a 'objdump' on the kernel.debug binary I do not see any CTF sections
> showing up?
>
>
> --
> Shrikanth R K
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