Re: [PATCH v4 07/39] x86: Add user control-protection fault handler

Borislav Petkov
2023-01-04T12:50:23Z

On Wed, Dec 21, 2022 at 09:42:50PM +0000, Edgecombe, Rick P wrote:
> Oh, you mean the whole Kconfig thing. Yea, I mean I see the point about
> typical configs. But at least CONFIG_X86_CET seems consistent with
> CONFIG_INTEL_TDX_GUEST, CONFIG_IOMMU_SVA, etc.
>
> What about moving it out of traps.c to a cet.c, like
> exc_vmm_communication for CONFIG_AMD_MEM_ENCRT? Then the inclusion
> logic lives in the build files, instead of an ifdef.

Yeah, that definitely sounds cleaner. Another example would be the #MC handler
being in mce code and not in traps.c.

So yeah, the reason why I'm even mentioning this is that I get an allergic
reaction when I see unwieldy ifdeffery in one screen worth of code. But this is
just me. :)

> One aspect that has come up a couple of times, is how closely related
> all these CET features are (or aren't). Shadow stack and IBT are mostly
> separate, but do share an xfeature and an exception type. Similarly for
> supervisor and user mode support for either of the CET features. So
> maybe that is what is unusual here. There are some aspects that make
> them look like separate features, which leads people to think they
> should be separate in the code. But actually separating them leads to
> excess ifdefery.

Yeah, I think you solved that correctly by having the common X86_CET symbol
selected by the two.

Thx.

--
Regards/Gruss,
Boris.