[PATCH] arm64: Introduce sysctl to disable pointer authentication

[Will Deacon]

On Tue, Jul 07, 2020 at 06:32:32PM +0100, Steve Capper wrote:
> Pointer authentication is a mandatory feature in the Armv8.3
> architecture that provides protection against return oriented
> programming attacks. (meaning that all Arm CPUs targetting at least
> Armv8.3 will have this feature).
> 
> Once CONFIG_ARM64_PTR_AUTH=y, any systems with the hardware support for
> pointer authentication will automatically have it enabled by the kernel.
> 
> There are, however, situations where end users may want to disable
> pointer authentication. One could be tracking down/working around a bug
> in userspace relating to pointer auth. Also, one may wish to quantify
> the performance overhead of pointer auth by running a workload
> with/without it.

If you're debugging userspace, just recompile your userspace application
without ptr auth, in the same way that you might recompile with -g.

The performance argument sucks; this stuff needs to be fast otherwise it's
pointless. If you really need that last bit of speed, try Gentoo ;)

Will