Abstract

The invention is a debugger which is part of the operating system of a multi-programmable digital data processor with virtual memory. The debugger can identify and correct faults in an embedded operating system of a multi-programmable digital data processor having hardware-controlled process exchange. The debugger is capable of suspending and effectively restarting processes in a primary or second central processing unit, as well as selectively accessing, reading, and/or modifying data at real or virtual memory locations. Further, the debugger can look ahead, using a next instruction prediction function, and determine the location of the next-to-be executed instruction. The debugger can then replace the previous breakpoint with the instruction the break point had originally replaced, and put the breakpoint after the next-to-be executed instruction. The debugger is also capable of simulating the local execution of a replaced instruction and restarting suspended processes. In this way the debugger can be used in single-step fashion to cause process suspension after every instruction in a sequence of code.

Other References

• "Debugging and Monitoring", Communications of the CACM, Jan. 1978, vol. 21, p. 89
• "Exceptions Occurring as the Consequence of an Instruction Start", VAX11 Architecture Handbook, Digital, pp. 304-313
• VAX11 780 Technical Summary, Digital, pp. 4-22-4-23