Re: [PATCH v2 5/5] powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and 8xx

[Michael Ellerman]

Luis Chamberlain <mcgrof@xxxxxxxxxx> writes:
> On Thu, Jan 27, 2022 at 11:28:12AM +0000, Christophe Leroy wrote:
>> book3s/32 and 8xx have a separate area for allocating modules,
>> defined by MODULES_VADDR / MODULES_END.
>> 
>> On book3s/32, it is not possible to protect against execution
>> on a page basis. A full 256M segment is either Exec or NoExec.
>> The module area is in an Exec segment while vmalloc area is
>> in a NoExec segment.
>> 
>> In order to protect module data against execution, select
>> ARCH_WANTS_MODULES_DATA_IN_VMALLOC.
>> 
>> For the 8xx (and possibly other 32 bits platform in the future),
>> there is no such constraint on Exec/NoExec protection, however
>> there is a critical distance between kernel functions and callers
>> that needs to remain below 32Mbytes in order to avoid costly
>> trampolines. By allocating data outside of module area, we
>> increase the chance for module text to remain within acceptable
>> distance from kernel core text.
>> 
>> So select ARCH_WANTS_MODULES_DATA_IN_VMALLOC for 8xx as well.
>> 
>> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
>> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
>> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
>> Cc: Paul Mackerras <paulus@xxxxxxxxx>
>
> Cc list first and then the SOB.

Just delete the Cc: list, it's meaningless.

cheers