Re: [RFC][PATCH 6/6] objtool: Add IBT validation / fixups

Joao Moreira
2022-02-09T02:45:12Z

>> Note: This feature was already submitted for upstreaming with the
>> llvm-project: https://reviews.llvm.org/D116070
>
> Ah nice; I see this has been committed now.

Yes, but then some front-end changes also required this fix
https://reviews.llvm.org/D118052, which is currently under review
(posting this here in case someone is trying this out).

>
> Given that IBT will need to work with both Clang and gcc, I suspect the
> objtool approach will still end up needing to do all the verification.
>
> (And as you say, it has limited visibility into assembly.)

Agreed that at this point objtool provides more coverage. Yet, besides
being an attempt to relief objtool and improve a bit the compiler
support as mentioned in the series cover letter, it is still nice to
reduce the left-over nops and fixups which end-up scattered all around.

FWIIW, https://reviews.llvm.org/D118438 and
https://reviews.llvm.org/D118355 are also being cooked. Comments and
ideas for new approaches or improvements in the compiler support for
this are very welcome :)

Tks,
Joao