4:264
Volume 4: Base IA-32 Instruction Reference
LGDT/LIDT—Load Global/Interrupt Descriptor Table Register
Description
Loads the values in the source operand into the global descriptor table register (GDTR)
or the interrupt descriptor table register (IDTR). The source operand is a pointer to 6
bytes of data in memory that contains the base address (a linear address) and the limit
(size of table in bytes) of the global descriptor table (GDT) or the interrupt descriptor
table (IDT). If operand-size attribute is 32 bits, a 16-bit limit (lower 2 bytes of the
6-byte data operand) and a 32-bit base address (upper 4 bytes of the data operand)
are loaded into the register. If the operand-size attribute is 16 bits, a 16-bit limit (lower
2 bytes) and a 24-bit base address (third, fourth, and fifth byte) are loaded. Here, the
high-order byte of the operand is not used and the high-order byte of the base address
in the GDTR or IDTR is filled with zeros.
The LGDT and LIDT instructions are used only in operating-system software; they are
not used in application programs. They are the only instructions that directly load a
linear address (that is, not a segment-relative address) and a limit in protected mode.
They are commonly executed in real-address mode to allow processor initialization prior
to switching to protected mode.
Operation
IF Itanium System Environment THEN IA-32_Intercept(INST,LGDT/LIDT);
IF instruction is LIDT
THEN
IF OperandSize = 16
THEN
IDTR(Limit)
SRC[0:15];
IDTR(Base)
SRC[16:47] AND 00FFFFFFH;
ELSE (* 32-bit Operand Size *)
IDTR(Limit)
SRC[0:15];
IDTR(Base)
SRC[16:47];
FI;
ELSE (* instruction is LGDT *)
IF OperandSize = 16
THEN
GDTR(Limit)
SRC[0:15];
GDTR(Base)
SRC[16:47] AND 00FFFFFFH;
ELSE (* 32-bit Operand Size *)
GDTR(Limit)
SRC[0:15];
GDTR(Base)
SRC[16:47];
FI;
FI;
Flags Affected
None.
Opcode
Instruction
Description
0F 01 /2
LGDT
m16&32
Load
m
into GDTR
0F 01 /3
LIDT
m16&32
Load
m
into IDTR
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...