Importance

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Abstract

A subroutine execution time tracer that is able to trace execution times of software subroutines regardless of whether the subroutines are invoked or exited using standard or non-standard subroutine calling conventions is described. A head patch is placed at the beginning of a software subroutine, and a tail patch is placed at the end of the software routine. The invention uses the head patch to examine the return address on the system stack before replacing the return address with the address of a tail patch. If the return address on the system stack already corresponds to a tail patch, then a counter associated with the tail patch is incremented. The counter serves to notify the tail patch that when invoked it must log an additional exit event. This allows subroutines which 'jump' to other subroutines (i.e., non-standard subroutine calls) to be properly traced. The invention also configures the tail patch as an internal code stack. The code stack ensures that every exit event will be properly logged and the subroutines will have been successfully traced regardless of whether the subroutines have modified the system stack with non-standard calling conventions. The invention can be implemented as a method, an apparatus, a system or a computer readable medium.

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First Claim