Re: [PATCH v3 00/36] arm64/gcs: Provide support for GCS in userspace

[Mark Brown]

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:

> > 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).

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