Intel IA-32 Manuale Utente
5-14 Vol. 3A
INTERRUPT AND EXCEPTION HANDLING
5.12
EXCEPTION AND INTERRUPT HANDLING
The processor handles calls to exception- and interrupt-handlers similar to the way it handles
calls with a CALL instruction to a procedure or a task. When responding to an exception or inter-
rupt, the processor uses the exception or interrupt vector as an index to a descriptor in the IDT.
If the index points to an interrupt gate or trap gate, the processor calls the exception or interrupt
handler in a manner similar to a CALL to a call gate (see Section 4.8.2, “Gate Descriptors,”
calls with a CALL instruction to a procedure or a task. When responding to an exception or inter-
rupt, the processor uses the exception or interrupt vector as an index to a descriptor in the IDT.
If the index points to an interrupt gate or trap gate, the processor calls the exception or interrupt
handler in a manner similar to a CALL to a call gate (see Section 4.8.2, “Gate Descriptors,”
Figure 5-2. IDT Gate Descriptors
31
16 15
13
14
12
8 7
0
P
Offset 31..16
D
P
P
L
0
4
31
16 15
0
Segment Selector
Offset 15..0
0
0
1
1
D
Interrupt Gate
DPL
Offset
P
Selector
Offset
P
Selector
Descriptor Privilege Level
Offset to procedure entry point
Segment Present flag
Segment Selector for destination code segment
Offset to procedure entry point
Segment Present flag
Segment Selector for destination code segment
31
16 15
13
14
12
8 7
0
P
D
P
P
L
0
4
31
16 15
0
TSS Segment Selector
0
1
0
1
0
Task Gate
4
5
0 0 0
31
16 15
13
14
12
8 7
0
P
Offset 31..16
D
P
P
L
0
4
31
16 15
0
Segment Selector
Offset 15..0
0
1
1
1
D
Trap Gate
4
5
0 0 0
Reserved
Size of gate: 1 = 32 bits; 0 = 16 bits
D