On Wed, Feb 26, 2020 at 5:16 PM Dave Hansen [off-list ref] wrote:

On 2/26/20 5:02 PM, H.J. Lu wrote:

quoted

quoted

That way everybody with old toolchains can still build the kernel (and
run/test code with your config option on, btw...).

CET requires a complete new OS image from kernel, toolchain, run-time.
CET enabled kernel without the rest of updated OS won't give you CET
at all.

If you require a new toolchain, nobody even builds your fancy feature.
Probably including 0day and all of the lazy maintainers with crufty old
distros.

GCC 8 or above is needed since vDSO must be compiled with
--fcf-protection=branch.

The point isn't to actually run CET at all.  The point is to get as many
people as possible testing as much of it as possible.  Testing includes
compile testing, static analysis and bloat watching.  It also includes
functional and performance testing when you've got the feature compiled
in but unavailable at runtime.  Did this hurt anything even when I'm not
using it?

I will leave the CET toolchain issue to Yu-cheng.

-- 
H.J.