Re: [PATCH v3 1/1] x86/fred: Fix INT80 emulation for FRED

[Xin Li]

On 4/17/2024 2:38 AM, Borislav Petkov wrote:
> On Tue, Apr 16, 2024 at 11:30:01PM -0700, Xin Li (Intel) wrote:
> > 3) The FRED kernel entry handler does *NOT* dispatch INT instructions,
> >     which is of event type EVENT_TYPE_SWINT, so compared with
> >     do_int80_emulation(), there is no need to do any user mode check.
>
> What does that mean?
>
> An event handler doesn't dispatch INT insns?
>
> /me is confused.

Maybe better to say?

The FRED kernel entry handler fred_entry_from_kernel() calls 
fred_bad_type() if an event is of type EVENT_TYPE_SWINT because Kernel 
does not use INT insns! So if the kernel is handling an INT insn, it can 
only be from a user level application.


> > + * A dedicated FRED INT80 handler duplicates quite a bit of the code in
> > + * do_int80_emulation(), but it avoids sprinkling more tests and seems
> > + * more readable. Just remember that we can always unify common stuff
> > + * later if it turns out that it won't diverge anymore, i.e., after the
> > + * FRED code settles.
> > + */
>
> And this is talking about duplication above and that text is duplicated
> from the commit message. :)

I wanted to keep it as a TODO.  I can remove it in the next iteration.

> I'll zap it when applying.
>
> Thx.