Intel 253666-024US User Manual
Page 605
Vol. 2A 3-559
INSTRUCTION SET REFERENCE, A-M
LSL—Load Segment Limit
•
Checks that the descriptor type is valid for this instruction. All code and data
segment descriptors are valid for (can be accessed with) the LSL instruction. The
valid special segment and gate descriptor types are given in the following table.
•
If the segment is not a conforming code segment, the instruction checks that the
specified segment descriptor is visible at the CPL (that is, if the CPL and the RPL
of the segment selector are less than or equal to the DPL of the segment
selector).
If the segment descriptor cannot be accessed or is an invalid type for the instruction,
the ZF flag is cleared and no value is loaded in the destination operand.
Operation
IF SRC(Offset) > descriptor table limit
THEN ZF ← 0; FI;
Table 3-60. Segment and Gate Descriptor Types
Type
Protected Mode
IA-32e Mode
Name
Valid
Name
Valid
0
Reserved
No
Upper 8 byte of a 16-
Byte descriptor
Yes
1
Available 16-bit TSS
Yes
Reserved
No
2
LDT
Yes
LDT
Yes
3
Busy 16-bit TSS
Yes
Reserved
No
4
16-bit call gate
No
Reserved
No
5
16-bit/32-bit task
gate
No
Reserved
No
6
16-bit interrupt gate
No
Reserved
No
7
16-bit trap gate
No
Reserved
No
8
Reserved
No
Reserved
No
9
Available 32-bit TSS
Yes
64-bit TSS
Yes
A
Reserved
No
Reserved
No
B
Busy 32-bit TSS
Yes
Busy 64-bit TSS
Yes
C
32-bit call gate
No
64-bit call gate
No
D
Reserved
No
Reserved
No
E
32-bit interrupt gate
No
64-bit interrupt gate
No
F
32-bit trap gate
No
64-bit trap gate
No