Instruction Set LSL
LSL -- Load Segment Limit
LSL -- Load Segment Limit
Opcode Instruction Clocks Description
0F 03 /r LSL r16,r/m16 pm=20/21 Load: r16 = segment limit,
selector r/m16 (byte granular)
0F 03 /r LSL r32,r/m32 pm=20/21 Load: r32 = segment limit,
selector r/m32 (byte granular)
0F 03 /r LSL r16,r/m16 pm=25/26 Load: r16 = segment limit,
selector r/m16 (page granular)
0F 03 /r LSL r32,r/m32 pm=25/26 Load: r32 = segment limit,
selector r/m32 (page granular)
Description
The LSL instruction loads a register with an unscrambled segment limit,
and sets ZF to 1, provided that the source selector is visible at the CPL
weakened by RPL, and that the descriptor is a type accepted by LSL.
Otherwise, ZF is cleared to 0, and the destination register is unchanged.
The segment limit is loaded as a byte granular value. If the descriptor
has a page granular segment limit, LSL will translate it to a byte limit
before loading it in the destination register (shift left 12 the 20-bit
"raw" limit from descriptor, then OR with 00000FFFH).
The 32-bit forms of this instruction store the 32-bit byte granular limit
in the 16-bit destination register.
Code and data segment descriptors are valid for LSL.
The valid special segment and gate descriptor types for LSL are given
in the following table:
Type Name Valid/Invalid
0 Invalid Invalid
1 Available 80286 TSS Valid
2 LDT Valid
3 Busy 80286 TSS Valid
4 80286 call gate Invalid
5 80286/80386 task gate Invalid
6 80286 trap gate Invalid
7 80286 interrupt gate Invalid
8 Invalid Valid
9 Available 80386 TSS Valid
A Invalid Invalid
B Busy 80386 TSS Valid
C 80386 call gate Invalid
D Invalid Invalid
E 80386 trap gate Invalid
F 80386 interrupt gate Invalid
Flags Affected
ZF as described above
Protected Mode Exceptions
#GP(0) for an illegal memory operand effective address in the CS, DS,
ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment;
#PF(fault-code) for a page fault
Real Address Mode Exceptions
Interrupt 6; LSL is not recognized in Real Address Mode
Virtual 8086 Mode Exceptions
Same exceptions as in Real Address Mode