Intel 253668-032US Manual De Usuario
5-4 Vol. 3
PROTECTION
Many different styles of protection schemes can be implemented with these fields
and flags. When the operating system creates a descriptor, it places values in these
fields and flags in keeping with the particular protection style chosen for an operating
system or executive. Application program do not generally access or modify these
fields and flags.
and flags. When the operating system creates a descriptor, it places values in these
fields and flags in keeping with the particular protection style chosen for an operating
system or executive. Application program do not generally access or modify these
fields and flags.
Figure 5-1. Descriptor Fields Used for Protection
Base 23:16
31
24 23 22 21 20 19
16 15
13
14
12 11
8 7
0
P
Base 31:24
G
D
P
P
L
Type
1
0
4
31
16 15
0
Base Address 15:00
Segment Limit 15:00
0
Base 23:16
A
V
V
L
Limit
19:16
B
A
W
E
0
Data-Segment Descriptor
31
24 23 22 21 20 19
16 15
13
14
12 11
8 7
0
P
Base 31:24
G
D
P
P
L
Type
1
0
4
31
16 15
0
Base Address 15:00
Segment Limit 15:00
0
Base 23:16
A
V
V
L
Limit
19:16
D
A
R
C
1
Code-Segment Descriptor
31
24 23 22 21 20 19
16 15
13
14
12 11
8 7
0
P
Base 31:24
G
D
P
P
L
Type
0
4
31
16 15
0
Base Address 15:00
Segment Limit 15:00
0
Limit
19:16
System-Segment Descriptor
A
B
C
D
DPL
C
D
DPL
Accessed
Big
Conforming
Default
Descriptor Privilege Level
Conforming
Default
Descriptor Privilege Level
Reserved
E
G
R
LIMIT
W
P
G
R
LIMIT
W
P
Expansion Direction
Granularity
Readable
Segment Limit
Writable
Present
Granularity
Readable
Segment Limit
Writable
Present
0
AVL Available to Sys. Programmer’s