Intel 253666-024US - Manual (Page 577)

Vol. 2A 3-531
INSTRUCTION SET REFERENCE, A-M
LDS/LES/LFS/LGS/LSS—Load Far Pointer
FI;
SegmentRegister ← SegmentSelector(SRC) ;
SegmentRegister ← SegmentDescriptor([SRC]);
FI;
ELSE IF FS, or GS is loaded with a NULL selector:
THEN
SegmentRegister ← NULLSelector;
SegmentRegister(DescriptorValidBit) ← 0; FI; (* Hidden flag;
not accessible by software *)
FI;
DEST ← Offset(SRC);
PREOTECTED MODE OR COMPATIBILITY MODE;
IF SS is loaded
THEN
IF SegementSelector = NULL
THEN #GP(0);
ELSE IF Segment selector index is not within descriptor table limits
or segment selector RPL ≠ CPL
or access rights indicate nonwritable data segment
or DPL
≠
CPL
THEN #GP(selector); FI;
ELSE IF Segment marked not present
THEN #SS(selector); FI;
FI;
SS ← SegmentSelector(SRC);
SS ← SegmentDescriptor([SRC]);
ELSE IF DS, ES, FS, or GS is loaded with non-NULL segment selector
THEN IF Segment selector index is not within descriptor table limits
or access rights indicate segment neither data nor readable code segment
or segment is data or nonconforming-code segment
and (RPL > DPL or CPL > DPL)
THEN #GP(selector); FI;
ELSE IF Segment marked not present
THEN #NP(selector); FI;
FI;
SegmentRegister ← SegmentSelector(SRC) AND RPL;
SegmentRegister ← SegmentDescriptor([SRC]);
FI;
ELSE IF DS, ES, FS, or GS is loaded with a NULL selector:
THEN
SegmentRegister ← NULLSelector;
SegmentRegister(DescriptorValidBit) ← 0; FI; (* Hidden flag;
not accessible by software *)