Re: [PATCH v3] PowerPC: Replace kretprobe with rethook

[Naveen N Rao <naveen@kernel.org>]

Masami Hiramatsu wrote:
> On Thu, 27 Jun 2024 09:21:01 -0400
> Abhishek Dubey <adubey@linux.ibm.com> wrote:
> 
>> +/* rethook initializer */
>> +int __init arch_init_kprobes(void)
>> +{
>> +	return register_kprobe(&trampoline_p);
>> +}
> 
> No, please don't use arch_init_kprobes() for initializing rethook, since
> rethook is used from fprobe too (at this moment).
> 
> If you want to make it relays on kprobes, you have to make a dependency
> in powerpc's kconfig, e.g.
> 
> select HAVE_RETHOOK if KPROBES
> 
> But I don't recommend it.

Given that kretprobe has always worked this way on powerpc, I think this
is a fair tradeoff. We get to enable fprobes on powerpc only if kprobes
is also enabled.

Longer term, it would certainly be nice to get rid of that probe, and to
expand the trampoline to directly invoke the rethook callback.


Thanks,
Naveen