[PATCH] powerpc/64: Implement arch_within_stack_frames

[Nicholas Piggin]

On Thu Dec 15, 2022 at 10:17 AM AEST, Segher Boessenkool wrote:
> On Wed, Dec 14, 2022 at 09:39:25PM +1000, Nicholas Piggin wrote:
> > What about just copying x86's implementation including using
> > __builtin_frame_address(1/2)? Are those builtins reliable for all
> > our targets and compiler versions?
>
> __builtin_frame_address(n) with n > 0 is specifically not supported, not
> on any architecture; it does not work in all situations on *any* arch,
> and not in *any* situation on some archs.

No, but the particular case of powerpc where we have frame pointers and
calling from a function where we know we have at least n + 1 frames on
the stack, it would be okay, right? The code is not really different
than using r1 directly and dereferencing that.

Thanks,
Nick