Intel IA-32 - Manual (Page 192)

5-16 Vol. 3A
INTERRUPT AND EXCEPTION HANDLING
When the processor performs a call to the exception- or interrupt-handler procedure:
•
If the handler procedure is going to be executed at a numerically lower privilege level, a
stack switch occurs. When the stack switch occurs:
a. The segment selector and stack pointer for the stack to be used by the handler are
obtained from the TSS for the currently executing task. On this new stack, the
processor pushes the stack segment selector and stack pointer of the interrupted
procedure.
b. The processor then saves the current state of the EFLAGS, CS, and EIP registers on
the new stack (see Figures 5-4).
c. If an exception causes an error code to be saved, it is pushed on the new stack after the
EIP value.
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If the handler procedure is going to be executed at the same privilege level as the
interrupted procedure:
a. The processor saves the current state of the EFLAGS, CS, and EIP registers on the
current stack (see Figures 5-4).
b. If an exception causes an error code to be saved, it is pushed on the current stack after
the EIP value.