Intel IA-32 Manuale Utente
6-12 Vol. 3A
TASK MANAGEMENT
Figure 6-7 illustrates how a task gate in an LDT, a task gate in the GDT, and a task gate in the
IDT can all point to the same task.
IDT can all point to the same task.
6.3
TASK SWITCHING
The processor transfers execution to another task in one of four cases:
•
The current program, task, or procedure executes a JMP or CALL instruction to a TSS
descriptor in the GDT.
descriptor in the GDT.
•
The current program, task, or procedure executes a JMP or CALL instruction to a task-gate
descriptor in the GDT or the current LDT.
descriptor in the GDT or the current LDT.
•
An interrupt or exception vector points to a task-gate descriptor in the IDT.
•
The current task executes an IRET when the NT flag in the EFLAGS register is set.
Figure 6-7. Task Gates Referencing the Same Task
LDT
Task Gate
TSS
GDT
TSS Descriptor
IDT
Task Gate
Task Gate