Re: [PATCH v5 04/27] x86/fpu/xstate: Add XSAVES system states for shadow stack

[Pavel Machek]

On Sun 2018-11-11 06:59:24, Andy Lutomirski wrote:
> 
> 
> > On Nov 11, 2018, at 3:31 AM, Pavel Machek <pavel@xxxxxx> wrote:
> > 
> > Hi!
> > 
> >>> +/*
> >>> + * State component 12 is Control flow Enforcement kernel states
> >>> + */
> >>> +struct cet_kernel_state {
> >>> +    u64 kernel_ssp;    /* kernel shadow stack */
> >>> +    u64 pl1_ssp;    /* ring-1 shadow stack */
> >>> +    u64 pl2_ssp;    /* ring-2 shadow stack */
> >> 
> >> Just write "privilege level" everywhere - not "ring".
> > 
> > Please just use word "ring". It is well estabilished terminology.
> > 
> > Which ring is priviledge level 1, given that we have SMM and
> > virtualization support?
> 
> To the contrary: CPL, DPL, and RPL are very well defined terms in the architecture manuals. âPLâ is privilege level. PL 1 is very well defined.
> 

"Priviledge level" is generic term. "CPL" I may recognize as
Intel-specific. "priviledge level" I would not. So I'd really use
"ring" there. "CPL 1 shadow stack" would be okay, too I guess.

> SMM is SMM, full stop (unless dual mode or whatever itâs called is on, but AFAIK no one uses it).  VMX non-root CPL 1 is *still* privilege level 1.
> 
> In contrast, the security community likes to call SMM âring -1â, which is cute, but wrong from a systems programmer view. For example, SMMâs CPL can still range from 0-3.
> 

Regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
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