[RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

[Naveen N. Rao]

Nicholas Piggin wrote:
> Naveen N. Rao's on May 17, 2019 4:22 am:
> 
>> While enabling ftrace, we will first need to patch the preceding 'mflr 
>> r0' (which would now be a 'nop') with 'b +8', then use 
>> synchronize_rcu_tasks() and finally patch in 'bl _mcount()' followed by 
>> 'mflr r0'.
>> 
>> I think that's what you meant, just that my reference to patching 'mflr 
>> r0' with a 'b +8' should have called out that the mflr would have been 
>> nop'ed out.
> 
> I meant that we don't need the b +8 anywhere, because the mflr r0
> is harmless. Enabling ftrace just needs to patch in 'mflr r0', and
> then synchronize_rcu_tasks(), and then patch in 'bl _mcount'. I think?

Ah, that's a good point! That should be enough and it simplifies this 
further.


Thanks,
Naveen