Re: [PATCH 0/6] objtool: Add support for Arm64

From: Josh Poimboeuf
Date: Tue Apr 09 2019 - 23:39:23 EST

On Tue, Apr 09, 2019 at 10:43:18AM -0700, Ard Biesheuvel wrote:
> On Tue, 9 Apr 2019 at 06:53, Raphael Gault <raphael.gault@xxxxxxx> wrote:
> >
> > Hi,
> >
> > As of now, objtool only supports the x86_64 architecture but the
> > groundwork has already been done in order to add support for other
> > architecture without too much effort.
> >
> > This series of patches adds support for the arm64 architecture
> > based on the Armv8.5 Architecture Reference Manual.
> >
> I think it makes sense to clarify *why* we want this on arm64. Also,
> we should identify things that objtool does today that maybe we don't
> want on arm64, rather than buy into all of it by default.

Agreed, the "why" should at least be in the cover letter. From my
perspective, the "why" includes:

- Live patching - objtool stack validation is the foundation for a
reliable unwinder

- ORC unwinder - benefits include presumed improved overall performance
from disabling frame pointers, and the ability to unwind across
interrupts and exceptions

- PeterZ's new uaccess validation?