Messages in this thread | | | Subject | Re: [PATCH 0/6] objtool: Add support for Arm64 | From | Julien Thierry <> | Date | Wed, 10 Apr 2019 08:20:31 +0100 |
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On 10/04/2019 04:37, Josh Poimboeuf wrote: > 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@arm.com> 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 >
Yes, as I understand Live patching is a work in progress for arm64. Having objtool to provide more guarantees would be nice.
> - ORC unwinder - benefits include presumed improved overall performance > from disabling frame pointers, and the ability to unwind across > interrupts and exceptions >
I'm unsure this will be part of the plan. I believe so far arm64 code heavily relies on the presence of frame pointers. It's also part of the Aarch64 Procedure Call Standard.
But who knows.
> - PeterZ's new uaccess validation? >
Yes, we've reverted twice our implementation of user_access_begin/end() on arm64 because of the issue of potentially calling sleeping functions.
Once we have the base of objtool work, this would be one of the next work items.
Thanks,
-- Julien Thierry
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