Re: [PATCH 1/3] powerpc/code-patching: work around code patching verification in patching tests

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 26/11/2021 à 11:27, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of November 26, 2021 4:34 pm:
>>
>>
>> Le 26/11/2021 à 04:22, Nicholas Piggin a écrit :
>>> Code patching tests patch the stack and (non-module) vmalloc space now,
>>> which falls afoul of the new address check.
>>>
>>> The stack patching can easily be fixed, but the vmalloc patching is more
>>> difficult. For now, add an ugly workaround to skip the check while the
>>> test code is running.
>>
>> This really looks hacky.
>>
>> To skip the test, you can call do_patch_instruction() instead of calling
>> patch_instruction().
> 
> And make a do_patch_branch function. I thought about it, and thought
> this is sligtly easier.
> 

Anyway, as reported by Sachin the ftrace code also trips in the new 
verification. So I have submitted a patch to revert to the previous 
level of verification.

Then we can fix all this properly without going through a temporary hack 
and activate the verification again once every caller is fixed.

I was not able to reproduce Sachin's problem on PPC32. Could it be 
specific to PPC64 ?

Christophe