On Sun, Jul 02, 2023 at 06:03:42PM +0000, Edgecombe, Rick P wrote:

On Thu, 2023-06-29 at 17:07 +0100, szabolcs.nagy@arm.com wrote:

quoted

which means x86 linux will likely end up maintaining two incompatible
abis and the future one will need user code and build system changes,
not just runtime changes. it is not a small incremental change to add
alt shadow stack support for example.

quoted

i don't think the maintenance burden of two shadow stack abis is the
right path for arm64 to follow, so the shadow stack semantics will
likely become divergent not common across targets.

Unfortunately we are at a bit of an information asymmetry here because
the ARM spec and patches are not public. It may be part of the cause of
the confusion.

While the descriptive text bit of the spec is not yet integrated into
the ARM the architecture XML describing the instructions and system
registers is there, the document is numbered DDI0601:

    https://developer.arm.com/documentation/ddi0601/

The GCS specific instructions and system registers are all named
beginning with GCS, it's aarch64 only.

Hopefully I should have something out next week for the kernel.