Messages in this thread | | | Date | Wed, 17 Apr 2024 08:09:19 -0700 | Subject | Re: [PATCH v3 1/1] x86/fred: Fix INT80 emulation for FRED | From | "H. Peter Anvin" <> |
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On 4/17/24 08:06, Xin Li wrote: > 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. >
(Note: if we at some point in the future we may end up adding INT calls from the kernel, at least on FRED it would *still* not share the same code paths and so int $0x80 would not get dispatched.)
-hpa
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