Intel 64 and IA-32 Architectures Software Developers Manual Volume 2B, Instruction Set Reference, N-Z

4-130 Vol. 2B
INSTRUCTION SET REFERENCE, N-Z
64-BIT_MODE
IF FS, or GS is loaded with non-NULL selector;
THEN
IF segment selector index is outside descriptor table limits
OR segment is not a data or readable code segment
OR ((segment is a data or nonconforming code segment)
AND (both RPL and CPL > DPL))
THEN #GP(selector);
IF segment not marked present
THEN #NP(selector);
ELSE
SegmentRegister ← segment selector;
SegmentRegister ← segment descriptor;
FI;
FI;
IF FS, or GS is loaded with a NULL selector;
THEN
SegmentRegister ← segment selector;
SegmentRegister ← segment descriptor;
FI;
PREOTECTED MODE OR COMPATIBILITY MODE;
IF SS is loaded;
THEN
IF segment selector is NULL
THEN #GP(0);
FI;
IF segment selector index is outside descriptor table limits
or segment selector's RPL
≠ CPL
or segment is not a writable data segment
or DPL
≠ CPL
THEN #GP(selector);
FI;
IF segment not marked present
THEN #SS(selector);
ELSE
SS ← segment selector;
SS ← segment descriptor;
FI;
FI;