[RFC] Design + prototype: Multiple handler sets per probe address

[Ananth N Mavinakayanahalli]

William Cohen wrote:
> Ananth N Mavinakayanahalli wrote:
> 
>> Hi,
>>
>> Here is a design to support "Mulitple handler sets per address". I 
>> have also put in the i386 implementation based on this design.
>>
>> Some notes:
>>
>> - The interfaces to register, unregister, define handlers all remain
>> the same.
>> - A kprobe and jprobe cannot co-exist at the same location. (Ideas are 
>> welcome on how to support this).
>>
>> I have minimally tested the patch and it works(tm).
>>
>> Please let me know your thoughts on the design. I'd also appreciate if 
>> you could test the patch (diffed against 2.6.12-rc1-mm3) and provide 
>> feedback.
>>
>>
>> Thanks,
>> Ananth
> 
> 
> 
> I have been working on some simple testing to exercises the multiple 
> probes. It checks to make sure that probes are inserted and deleted as 
> expected. It has three probes at location.
> 
> I appologize for the verbose output. I have also attached output of the 
> test results. There are some warning about allocating sleeping function.

The warning appears only in one of the eight runs. Will investigate
this. A GFP_KERNEL/GFP_ATOMIC issue, probably - but if so, why only in
one of the eight runs? Beats me!

> It appears to be inserting and removing probes as expected.

Good to hear that!

> It seems like it would be useful to have unregister_kprobe() return 
> whether the operation was successful or not. Be able to catch cases were 
> code attempts to remove a probe twice.

Changing the existing interface :-) But I suppose users who don't care
about the return code may as well ignore it.

Thanks,
Ananth