, , :
1) (LDT) LDTR .
.. .
2 ) GDT, , .
,
3) , ( LDT ).
( ):
GDTR LDTR
4) ( , , )
:
, , 5- ( ):
7- 5-
6- 5- DPL ( )
4- 0- ( )
S (c ):
(0) LDT TSS
(1)
E (0) (1)
:
ED Expand Down :
o 0
o 1
W writeable (1 , 0 - )
A accessed ( , )
:
- conforming :
o 0 , CPL = DPL
o 1 , CPL >= DPL
R readable (1 , 0 - )
A accessed ( , )
1) - ( , ).
2)
( )
,
:
( ):
4 :
|
|
0
1, 2
3
:
DPL Descripror Privilege Level (DPL )
RPL Request Privilege Level (RPL (, ))
PL Current Privilege Level (RPL (, ))
EPL Effective Privilege Level . ?
. 2 : 00 01 10 11. DPL.
. TSS task state segment
:
-
EPL DPL :
EPL = max (RPL, CPL) -
CPL
RPL ,
DPL ,
-
,
EPL = DPL ,
.. .
-
CPL DPL, .