On 05/25/2010 01:36 PM, Mohammed Gamal wrote:
Any reference to back this up? I think rpl is valid regardless of
ss.unusable (i.e. loading selector 0003 results in an unusable segment with
rpl=3), but I don't see how dpl can be valid in an unusable segment.
Intel 64 and IA-32 Architectures Software Developer’s Manual Volume
3B, System Programming Guide, Part 2, Chapter 22, Section 22.3.1.2:
Checks on Guest Segment Registers.
You'll note that DS, ES, FS, GS checks are done when the segment is
usable. SS checks are not necessarily checked only when the segment is
usable.
Strange, but consistent with
If the unusable bit is 1, the base address, the segment limit, and the
remainder of the access rights are undefined after VM entry. The only
exceptions are the following:
— Bits 3:0 of the base address for SS are cleared to 0.
— SS.DPL: always loaded from the SS access-rights field. This will be
the current privilege level (CPL) after the VM entry completes.
— SS.B: set to 1.
— The base addresses for FS and GS: always loaded. On processors
that support Intel 64 architecture, the values loaded for base
addresses for FS and GS are also manifest in the FS.base and
GS.base MSRs.
— The base address for LDTR on processors that support Intel 64 archi-
tecture: set to an undefined but canonical value.
— Bits 63:32 of the base addresses for SS, DS, and ES on processors
that support Intel 64 architecture: cleared to 0.
So you are right.
Seems to me we can simplify vmx_get_cpl() on this basis to look at ss.dpl.
--
error compiling committee.c: too many arguments to function
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