如果在内核把特权级切换到用户态之前屏蔽 CPU 对软中断的响应，是不是就再也进不了内核态了？ 第1页

CLI — Clear Interrupt Flag

Description

In most cases, CLI clears the IF flag in the EFLAGS register and no other flags are affected. Clearing the IF flag causes the processor to ignore maskable external interrupts. The IF flag and the CLI and STI instruction have no effect on the generation of exceptions and NMI interrupts.

6.3.3 Software-Generated Interrupts

The INT n instruction permits interrupts to be generated from within software by supplying an interrupt vector number as an operand. For example, the INT 35 instruction forces an implicit call to the interrupt handler for interrupt 35.

Any of the interrupt vectors from 0 to 255 can be used as a parameter in this instruction. If the processor's predefined NMI vector is used, however, the response of the processor will not be the same as it would be from an NMI interrupt generated in the normal manner. If vector number 2 (the NMI vector) is used in this instruction, the NMI interrupt handler is called, but the processor’s NMI-handling hardware is not activated.

Interrupts generated in software with the INT n instruction cannot be masked by the IF flag in the EFLAGS register.

注意加粗部分。

另外，SYSENTER/SYSCALL都可以进内核态。

结论就是，不能。