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Unformatted text preview: inter from memory. Load SS:r16 with far pointer from memory. Load SS:r32 with far pointer from memory. Load SS:r64 with far pointer from memory. Load ES:r16 with far pointer from memory. Load ES:r32 with far pointer from memory. Load FS:r16 with far pointer from memory. Load FS:r32 with far pointer from memory. Load FS:r64 with far pointer from memory. Load GS:r16 with far pointer from memory. Load GS:r32 with far pointer from memory. Load GS:r64 with far pointer from memory. Description
Loads a far pointer (segment selector and offset) from the second operand (source operand) into a segment register and the first operand (destination operand). The source operand specifies a 48-bit or a 32-bit pointer in memory depending on the current setting of the operand-size attribute (32 bits or 16 bits, respectively). The instruction opcode and the destination operand specify a segment register/generalpurpose register pair. The 16-bit segment selector from the source operand is loaded into the segment register specified with the opcode (DS, SS, ES, FS, or GS). The 32-bit or 16-bit offset is loaded into the register specified with the destination operand. 3-522 Vol. 2 INSTRUCTION SET REFERENCE, A-M If one of these instructions is executed in protected mode, additional information from the segment descriptor pointed to by the segment selector in the source operand is loaded in the hidden part of the selected segment register. Also in protected mode, a NULL selector (values 0000 through 0003) can be loaded into DS, ES, FS, or GS registers without causing a protection exception. (Any subsequent reference to a segment whose corresponding segment register is loaded with a NULL selector, causes a general-protection exception (#GP) and no memory reference to the segment occurs.) In 64-bit mode, the instruction's default operation size is 32 bits. Using a REX prefix in the form of REX.W promotes operation to specify a source operand referencing an 80-bit pointer (16-bit selector, 64-bit offset) in memory. Using a REX prefix in the form of REX.R permits access to additional registers (R8-R15). See the summary chart at the beginning of this section for encoding data and limits. Operation
64-BIT_MODE IF SS is loaded THEN IF SegmentSelector = NULL and ( (RPL = 3) or (RPL 3 and RPL CPL) ) THEN #GP(0); ELSE IF descriptor is in non-canonical space THEN #GP(0); FI; 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 attempt to load DS, or ES THEN #UD; ELSE IF 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 > DP...
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This note was uploaded on 10/01/2013 for the course CPE 103 taught by Professor Watlins during the Winter '11 term at Mississippi State.
- Winter '11