[PATCH RFC 2/8] arm64: stacktrace: Add arch_within_stack_frames

[Kees Cook]

On Mon, Apr 18, 2022 at 09:22:11PM +0800, He Zhe wrote:
> This function checks if the given address range crosses frame boundary.
> It is based on the existing x86 algorithm, but implemented via stacktrace.
> This can be tested by USERCOPY_STACK_FRAME_FROM and
> USERCOPY_STACK_FRAME_TO in lkdtm.

Hi,

Thanks for doing this implementation! One reason usercopy hardening
didn't persue doing a "full" stacktrace was because it seemed relatively
expensive. Did you do any usercopy-heavily workload testing to see if
there was a noticeable performance impact?

It would be nice to block the exposure of canaries and PAC bits, though,
so I'm not opposed, but I'd like to get a better sense of how "heavy"
this might be.

Thanks!

-Kees

-- 
Kees Cook