Re: [PATCH 00/29] x86: Kernel IBT

[Peter Zijlstra]

On Mon, Feb 21, 2022 at 12:42:25AM -0800, Kees Cook wrote:

> >+void cet_disable(void)
> >+{
> >+	cr4_clear_bits(X86_CR4_CET);
> 
> I'd rather keep the pinning...

Uff. is that still enforced at this point?

> >+	wrmsrl(MSR_IA32_S_CET, 0);
> >+}
> 
> Eh, why not just require kexec to be IBT safe? That seems a reasonable
> exercise if we ever expect UEFI to enforce IBT when starting the
> kernel on a normal boot...

Well, it makes it impossible to kexec into an 'old' kernel. That might
not be very nice.