Re: [RFC PATCH 3/3] objtool/mcount: Add powerpc specific functions

[Josh Poimboeuf <jpoimboe@redhat.com>]

On Mon, Mar 28, 2022 at 10:14:38PM +0200, Peter Zijlstra wrote:
> > 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.
> 
> IIRC the major stumbling block for arm64 is the whole jump-table thing.
> Either they need to rely on compiler plugins to provide objtool that
> data (yuck, since we support at least 2 different compilers), disable
> jump-tables (yuck, for that limits code-gen just to please a tool) or
> use DWARF (yuck, because build times).

Well yeah, that was indeed the main technical issue but I seem to
remember some arm64 maintainers not really being sold on the value of
objtool regardless.

> There was a little talk about an impromptu 'abi' to communicate
> jump-table details to objtool without going full on DWARF, but that
> seems to have hit a dead end again.

Probably my fault, not enough hours in the day...

-- 
Josh