Christophe Leroy wrote:
Le 29/03/2022 à 14:01, Michael Ellerman a écrit :
Josh Poimboeuf <jpoim...@redhat.com> writes:
On Sun, Mar 27, 2022 at 09:09:20AM +0000, Christophe Leroy wrote:
What are current works in progress on objtool ? Should I wait Josh's
changes before starting looking at all this ? Should I wait for anything
else ?
I'm not making any major changes to the code, just shuffling things
around to make the interface more modular. I hope to have something
soon (this week). Peter recently added a big feature (Intel IBT) which
is already in -next.
Contributions are welcome, with the understanding that you'll help
maintain it ;-)
Some years ago Kamalesh Babulal had a prototype of objtool for ppc64le
which did the full stack validation. I'm not sure what ever became of
that.
From memory he was starting to clean the patches up in late 2019, but I
guess that probably got derailed by COVID. AFAIK he never posted
anything. Maybe someone at IBM has a copy internally (Naveen?).
Kamalesh had a WIP series to enable stack validation on powerpc. From
what I recall, he was waiting on and/or working with the arm64 folks
around some of the common changes needed in objtool.
FWIW, there have been some objtool patches for arm64 stack validation,
but the arm64 maintainers have been hesitant to get on board with
objtool, as it brings a certain maintenance burden. Especially for the
full stack validation and ORC unwinder. But if you only want inline
static calls and/or mcount then it'd probably be much easier to
maintain.
I would like to have the stack validation, but I am also worried about
the maintenance burden.
I guess we start with mcount, which looks pretty minimal judging by this
series, and see how we go from there.
I'm not sure mcount is really needed as we have recordmcount, but at
least it is an easy one to start with and as we have recordmount we can
easily compare the results and check it works as expected.
On the contrary, I think support for mcount in objtool is something we
want to get going soon (hopefully, in time for v5.19) given the issues
we are seeing with recordmcount:
- https://github.com/linuxppc/issues/issues/388
- https://lore.kernel.org/all/20220211014313.1790140-1-...@ozlabs.ru/
- Naveen
