操作系统 Interrupt 执行的具体步骤

本文内容主要摘抄于 Intel® 64 and IA-32 Architectures Software Developer's Manual，其详细介绍了 interrupt 执行的具体步骤以及对应stack的前后变化，因为写的非常好，所以在这里和大家分享下。

其实我一直在找相关方面的资料，但在读了网上的各种文章后，我还是有各种疑问，所以今天下决心读了下intel的官方manual（以前就知道，只是因为内容太多了，迟迟没有细看），发现写的非常详细，以前的很多疑问也都豁然开朗了。

再次证明，学习一个东西一定要先看官方资料。

下面就是 interrupt 执行的具体步骤：

If the code segment for the handler procedure has the same privilege level as the currently executing program or task, the handler procedure uses the current stack; if the handler executes at a more privileged level, the processor switches to the stack for the handler’s privilege level.

If no stack switch occurs, the processor does the following when calling an interrupt or exception handler (see Figure 6-5):

1. Pushes the current contents of the EFLAGS, CS, and EIP registers (in that order) on the stack.

2. Pushes an error code (if appropriate) on the stack.

3. Loads the segment selector for the new code segment and the new instruction pointer (from the interrupt gate or trap gate) into the CS and EIP registers, respectively.

4. If the call is through an interrupt gate, clears the IF flag in the EFLAGS register.

5. Begins execution of the handler procedure

If a stack switch does occur, the processor does the following:

1. Temporarily saves (internally) the current contents of the SS, ESP, EFLAGS, CS, and EIP registers.

2. Loads the segment selector and stack pointer for the new stack (that is, the stack for the privilege level being called) from the TSS into the SS and ESP registers and switches to the new stack.

3. Pushes the temporarily saved SS, ESP, EFLAGS, CS, and EIP values for the interrupted procedure’s stack onto the new stack.

4. Pushes an error code on the new stack (if appropriate).

5. Loads the segment selector for the new code segment and the new instruction pointer (from the interrupt gate or trap gate) into the CS and EIP registers, respectively.

6. If the call is through an interrupt gate, clears the IF flag in the EFLAGS register.

7. Begins execution of the handler procedure at the new privilege level.

A return from an interrupt or exception handler is initiated with the IRET instruction. The IRET instruction is similar to the far RET instruction, except that it also restores the contents of the EFLAGS register for the interrupted procedure. When executing a return from an interrupt or exception handler from the same privilege level as the interrupted procedure, the processor performs these actions:

1. Restores the CS and EIP registers to their values prior to the interrupt or exception.

2. Restores the EFLAGS register.

3. Increments the stack pointer appropriately.

4. Resumes execution of the interrupted procedure.

When executing a return from an interrupt or exception handler from a different privilege level than the interrupted procedure, the processor performs these actions:

1. Performs a privilege check.

2. Restores the CS and EIP registers to their values prior to the interrupt or exception.

3. Restores the EFLAGS register.

4. Restores the SS and ESP registers to their values prior to the interrupt or exception, resulting in a stack switch back to the stack of the interrupted procedure.

5. Resumes execution of the interrupted procedure

下面是对应stack的前后变化图：

希望对你有所帮助。

完。