Schedule Syllabus Project

Breakpoints

Breakpoints allow a user to specify a point in a program where execution should pause. This allows the user to inspect registers, memory, and generial program state.

Breakpoints need hardware support to work correctly. The basics steps are:

• Replace instruction with break/trap instruction (backup original instruction)
• Exception handler will be entered
• The user can inspect the program at this point
• When resumed, put the original instruction back
• Restart execution at the original instruction
• Somehow, restore the breakpoint
  • Some processesors can step one instruction
  • Otherwise, put a new breakpoint at the 'next' instruction
  • Once inside the exception handler, put original instruction back
  • Do any cleanup needed to fix restore breakpoint