Dynamic instrumentation of an executable program by means of causing a breakpoint at the entry point of a function and providing instrumentation code

An apparatus for dynamic instrumentation of an executable application program by an instrumentation program, the application program including a plurality of original functions, each original function having an entry point and an endpoint, comprising:

• means for patching the function entry points with breakpoint instructions;
• means for creating a shared memory segment for the instrumentation program and the application program;
• means for creating in the shared memory segment corresponding substitute functions including instrumentation code upon initial invocation of the original functions in the application program and in response to encountering the breakpoint instructions;
• and
• means for executing the substitute functions in lieu of the original functions in the application program.