Re: [PATCH v2 03/39] x86/cpufeatures: Add CPU feature flags for shadow stacks

Borislav Petkov
2022-10-14T16:21:01Z

On Thu, Sep 29, 2022 at 03:29:00PM -0700, Rick Edgecombe wrote:
> From: Yu-cheng Yu <yu-cheng.yu@intel.com>
>
> The Control-Flow Enforcement Technology contains two related features,
> one of which is Shadow Stacks. Future patches will utilize this feature
> for shadow stack support in KVM, so add a CPU feature flags for Shadow
> Stacks (CPUID.(EAX=7,ECX=0):ECX[bit 7]).
>
> To protect shadow stack state from malicious modification, the registers
> are only accessible in supervisor mode. This implementation
> context-switches the registers with XSAVES. Make X86_FEATURE_SHSTK depend
> on XSAVES.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: Kees Cook <keescook@chromium.org>

Reviewed-by: Borislav Petkov <bp@suse.de>

--
Regards/Gruss,
Boris.