On Tue, Aug 01, 2023 at 03:13:20PM +0100, Will Deacon wrote:

On Mon, Jul 31, 2023 at 02:43:09PM +0100, Mark Brown wrote:

quoted

The arm64 Guarded Control Stack (GCS) feature provides support for
hardware protected stacks of return addresses, intended to provide
hardening against return oriented programming (ROP) attacks and to make
it easier to gather call stacks for applications such as profiling.

Why is this better than Clang's software shadow stack implementation? It
would be nice to see some justification behind adding all this, rather
than it being an architectural tick-box exercise.

Mainly that it's hardware enforced (as the quoted paragraph says).  This
makes it harder to attack, and hopefully it's also a bit faster (how
measurable that might be will be an open question, but even NOPs in
function entry/exit tend to get noticed).