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

Le 26/11/2021 à 11:27, Nicholas Piggin a écrit :

Excerpts from Christophe Leroy's message of November 26, 2021 4:34 pm:

quoted

Le 26/11/2021 à 04:22, Nicholas Piggin a écrit :

quoted

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