Homework 8 on Writing Your Own Exception/Interrupt Handler

Andrew Sohn, Computer Science Department, New Jersey Institute of Technology

• Write an "Assembly handler" and a correspodning "C handler."
• Try to follow the steps below and also the ones discussed in class yesterday:
  • Obtain the IDT table address using inline assembly. See store_idt()/load_idt() for loading and storing the IDT base address.
  • Replace the high and low address of IDT entry n with the new high/low address, where n is an exception number.
  • The new high and low address that would go into the IDT entry will be defined by your own assembly handler.
  • Write your own assembly handler. Use this handler address as the new high & low in IDT.
  • Your assembly handler will call your own C handler.
  • Your C handler will print or do something to indicate that your C handler is activated.
  • Your C handler will terminate normally and return to your assembly handler.
  • Upon returning from your C handler, your assembly handler will jump to the original asm handler.
  • Find the original C handler address from System.map.
• The following statments in your application will generate a "divide error" exception with the message "Floating point exception."

      int i=1, j=0;
      printf("%d",i/j);
    

• Make sure to include some print statements to indicate that the handler is activated.
• Include your name and the nature of the exception/interrupt along with the condition(s) that triggered the event if possible.
• The above example is one of many possibilities. Check the web for more references and try several different techniques if your time allows.