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

Christophe Leroy [off-list ref] writes:

Le 03/02/2022 à 06:39, Michael Ellerman a écrit :

quoted

Luis Chamberlain [off-list ref] writes:

quoted

On Thu, Jan 27, 2022 at 11:28:12AM +0000, Christophe Leroy wrote:

quoted

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 <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <redacted>

Cc list first and then the SOB.

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

Was an easy way to copy you automatically with 'git send-email', but 
getting it through linuxppc-dev list is enough I guess ?

It's useful for making the tooling Cc the right people, it's fine to use
them for that.

But there's no value in committing them to the git history, I actively
strip them when applying. The fact that someone is Cc'ed on a patch
tells you nothing, given the volume of mail maintainers receive.

The link tag back to the original submission gives you the Cc list
anyway.

cheers