Computer method and apparatus for safe instrumentation of reverse executable program modules

Abstract

Computer method and apparatus allows instrumentation of program modules while maintaining exception-handling unwinding context. In the case of instrumenting procedure prologues, the invention preserves the calling context. A sanitized copy of the prologue and rewind instructions to reverse the effects of duplicate prologue instructions are employed.

What is claimed is:  
     
         1 . A computer usable medium having computer readable code thereon, for inserting binary instrumentation code into a binary image of a subject program, the computer readable code when executed on a computer processor causing the processor to perform the steps of: 
 identifying a portion of the subject program into which insertion of instrumentation code is desired, the identified portion including an original prologue of a program procedure;    duplicating the identified portion such that a working copy of the identified portion is formed, said duplicating including placing the working copy before the identified portion;    removing instructions from the working copy such that only instructions necessary to restore calling context remains;    instrumenting the identified portion; and    enabling the working copy for use during exception handling of the subject program and otherwise effecting use of the instrumented identified portion in the subject program.    
     
     
         2 . A computer usable medium as claimed in  claim 1  further causing the processor to provide reverse instructions for reverse effecting the working copy of the identified portion.  
     
     
         3 . A computer usable medium as claimed in  claim 1  wherein the step of enabling the working copy includes setting constructs such that the working copy serves as a prologue and the original prologue is executed as part of a main body of the program procedure.  
     
     
         4 . Computer apparatus for inserting binary instrumentation code into a binary image of a subject program comprising: 
 means for identifying a portion of the subject program into which insertion of instrumentation code is desired, the identified portion including an original prologue of a program procedure;    means for duplicating the identified portion such that a working copy of the identified portion is formed, said duplicating including placing the working copy before the identified portion;    means for removing instructions from the working copy such that only instructions necessary to restore calling context remains;    means for instrumenting the identified portion; and    means for enabling the working copy for use during exception handling of the subject program and otherwise effecting use of the instrumented identified portion in the subject program.    
     
     
         5 . Computer apparatus as claimed in  claim 4  further comprising means for providing reverse instructions for reverse effecting the working copy of the identified portion.  
     
     
         6 . Computer apparatus as claimed in  claim 4  wherein the means for enabling the working copy further sets constructs such that the working copy serves as a prologue and the original prologue is executed as part of a main body of the program procedure.