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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
Содержание ITANIUM ARCHITECTURE
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Страница 7: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 199: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Страница 269: ...4 262 Volume 4 Base IA 32 Instruction Reference LES Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 270: ...Volume 4 Base IA 32 Instruction Reference 4 263 LFS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 273: ...4 266 Volume 4 Base IA 32 Instruction Reference LGS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 288: ...Volume 4 Base IA 32 Instruction Reference 4 281 LSS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 352: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Страница 368: ...Volume 4 Base IA 32 Instruction Reference 4 361 SHL SHR Shift Instructions See entry for SAL SAR SHL SHR ...
Страница 373: ...4 366 Volume 4 Base IA 32 Instruction Reference SIDT Store Interrupt Descriptor Table Register See entry for SGDT SIDT ...
Страница 589: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Страница 590: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Страница 591: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 603: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...
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