LGDT
Usage: LGDT src Modifies flags: None
Loads a value from an operand into the Global Descriptor Table (GDT) register.
Load Descriptor Tables
LGDT mem ; 0F 01 /2 [286,PRIV]
LIDT mem ; 0F 01 /3 [286,PRIV]
LLDT r/m16 ; 0F 00 /2 [286,PRIV]
LGDT and LIDT both take a 6-byte memory area as an operand: they load a 32-bit linear address and a 16-bit size limit from that area (in the opposite order) into the GDTR (global descriptor table register) or IDTR (interrupt descriptor table register). These are the only instructions which directly use addresses, rather than segment/offset pairs.
LLDT takes a segment selector as an operand. The processor looks up that selector in the GDT and stores the limit and base address given there into the LDTR (local descriptor table register).
See also SGDT, SIDT and SLDT.
Example:
lgdt Label