Using NuMega SoftICE

Interrupt Descriptor Table and SoftICE "IDT" command(IDT)

Intel x86 processor architecure defines a data strucutre called Interrupt Descriptor Table (IDT) and its entry, Interrupt Gate (and Task Gate). This is the central location through which all of the "interrupt" is handled. In essence, IDT is a list of "interrupt handlers" who is responsible for handling a particular interrupt.

If you look at each entry of the table, you notice that it is basically a saved "selector:offset" of a handler. This is the major difference from entries of GDT and LDT (for GDT, see How Windows NT uses GDT to implement "kernel mode" and "user mode") where GDT describes a range of memory and its attribute but not points to a routine.

SoftICE "IDT" command lists the contents of the table entries. The figure below shows how raw memory of IDT relates to IDT command output.

 

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