Stack clearing device and method

• US 6,550,058 B1
• Filed: 02/03/2000
• Issued: 04/15/2003
• Est. Priority Date: 02/03/2000
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wynn, Allen C.
• Primary Examiner(s): Dam, Tuan Q.
• Assistant Examiner(s): Steelman, Mary J.
• Application Number:
  US09/497,606
• Time in Patent Office: 1,167 Days
• Field of Search: 717/152, 717/157, 717/158, 717/159, 717/124, 717/127, 717/128, 717/130, 717/131, 717/132, 717/133, 717/154, 711/100, 711/103, 712/202, 713/189, 713/193, 713/194, 713/200, 713/201, 713/185
• US Class Current: 717/158
• CPC Class Codes: G06F 21/52 during program execution, e.g. stack integrity ; Preventing unwanted data erasure; Buffer overflow
• CPC Class Codes: G06F 21/62 Protecting access to data via a platform, e.g. using keys or access control rules
• CPC Class Codes: G06F 2221/2143 Clearing memory, e.g. to prevent the data from being stolen
• CPC Class Codes: G06F 8/41 Compilation
• CPC Class Codes: G06F 9/4486 Formation of subprogram jump address

Abstract

A method for removing residual data from a computer program stack prior to returning control to a calling or controlling process with system and method for automatic inclusion thereof into software application programs at the time of production of executable code. Two methods, one for removing residual data from a relatively small stack frame and another for removing residual data from a large stack frame, are automatically inserted into application program code during an enhanced compiling method. Two compiler controls allow a software designer to globally include the stack cleaning feature in all code being produced, or to selectively include the stack cleaning feature into certain indicated modules, code areas, or procedures.

Claims

1. A method of producing computer executable code for automatically clearing a computer program stack in computer memory, said program stack having a pointer which identifies a memory address value for a top of the stack, and said program stack being operable for storing and passing of data between calling and called processes and subroutines, said method comprising the steps of:

providing a computer program source code compiler having a user control to enable and disable automatic generation of executable code to clear computer stack memory;

receiving at least one computer program source code module and an associated user compiler control;

performing analysis on said computer program source code to find and identify instances of process and subroutine call and return operations; and

inserting stack clearing computer program code into said computer program source code prior to return operations and following call operations such that when the modified computer program code is compiled and executed, stack memory utilized by called processes and subroutines will be cleared to prevent usage of residual data in the stack by other processes or subroutines, said insertion of stack clearing computer program code being inserted only if said user control indicates enablement of insertion of the code.

2. A method of producing computer executable code as set forth in claim 1 wherein the step of performing analysis to find and identify instances of process and subroutine call and return operations further comprises determining a stack frame size utilized by each called process and subroutine.

3. A method of producing computer executable code as set forth in claim 2 wherein the step of inserting stack clearing computer program code into said computer program source code prior to return operations and following call operations further comprises inserting stack clearing computer program code which clears the entire stack frame utilized by each called process or subroutine.

4. A method of producing computer executable code as set forth in claim 1 wherein said step of inserting stack clearing computer program code into said computer program source code prior to return operations further comprises inserting computer program code which clears stack memory of argument values conveyed by the calling process to each called process or subroutine using the stack memory.

5. A method of producing computer executable code as set forth in claim 1 wherein said step of inserting stack clearing computer program code into said computer program source code prior to return operations further comprises inserting computer program code which clears stack memory of local data values generated by each called process or subroutine using the stack memory.

6. A method of producing computer executable code as set forth in claim 1 wherein said step of inserting stack clearing computer program code into said computer program source code following call operations further comprises inserting computer program code which clears stack memory of processor context values stored in stack memory by calling processes or routines.

7. A method of producing computer executable code as set forth in claim 1 wherein said step of inserting stack clearing computer program code into said computer program source code following call operations further comprises inserting computer program code which clears stack memory of return address values conveyed to each called process or subroutine using the stack memory.

8. A method of producing computer executable code as set forth in claim 1 wherein said step inserting stack clearing computer program code into said computer program source code if said user compiler control indicates enablement of insertion of the code further comprises inserting stack clearing code into computer program source code between a pair of enabling and disabling user compiler controls.

9. A method of producing computer executable code as set forth in claim 8 wherein said step inserting stack clearing computer program code into said computer program source code between a pair of enabling and disabling user compiler controls further comprises receiving an enabling pragma control and a disabling pragma control.

10. A method of producing computer executable code as set forth in claim 1 wherein said step inserting stack clearing computer program code into said computer program source code if said user compiler control indicates enablement of insertion of the code further comprises inserting stack clearing code into computer program source code in all computer program source code if a user compiler control selects global insertion for all computer program source code.

11. A method of producing computer executable code as set forth in claim 1 further comprises the step of receiving a user compiler control included in a compiler control file.

12. A method of producing computer executable code as set forth in claim 1 further comprises the step of receiving a user compiler control included in compiler invocation command argument.

13. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory, said program stack having a pointer which identifies a memory address value for a top of the stack, and said program stack being operable for storing and passing of data between calling and called processes and subroutines, said computer program product comprising:

a computer usable medium having computer readable compiler program code means embodied in said medium for compiling computer program source code, said compiler having a user compiler control to enable and disable automatic generation of executable code to clear computer stack memory;

a computer usable medium having computer readable program code means embodied in said medium for performing analysis of said computer program source code to find and identify instances of process and subroutine call and return operations; and

a computer usable medium having computer readable compiler program code means embodied in said medium for inserting stack clearing computer program code into said computer program source code prior to return operations and following call operations such that when the modified computer program code is compiled and executed, stack memory utilized by called processes and subroutines will be cleared to prevent usage of residual data in the stack by other processes or subroutines, said insertion of stack clearing computer program code being inserted only if said user control indicates enablement of insertion of the code.

14. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, wherein the computer readable program code means for performing analysis to find and identify instances of process and subroutine call and return operations further comprises computer readable program code means for determining a stack frame size utilized by each called process and subroutine.

15. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 14, wherein the computer readable program code means for inserting stack clearing computer program code into said computer program source code prior to return operations and following call operations further comprises computer readable program code means for inserting stack clearing computer program code which clears the entire stack frame utilized by each called process or subroutine.

16. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, wherein the computer readable program code means for inserting stack clearing computer program code into said computer program source code prior to return operations further comprises computer readable program code means for inserting computer program code which clears stack memory of argument values conveyed by the calling process to each called process or subroutine using the stack memory.

17. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, wherein said computer program means for inserting stack clearing computer program code into said computer program source code prior to return operations further comprises computer program means for inserting computer program code which clears stack memory of local data values generated by each called process or subroutine using the stack memory.

18. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, wherein said computer program means for inserting stack clearing computer program code into said computer program source code following call operations further comprises computer program means for inserting computer program code which clears stack memory of processor context values stored in stack memory by calling processes or routines.

19. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, wherein said computer program means for inserting stack clearing computer program code into said computer program source code following call operations further comprises computer program means for inserting computer program code which clears stack memory of return address values conveyed to each called process or subroutine using the stack memory.

20. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, wherein said user compiler control comprises a pair of enabling and disabling user compiler controls which enables insertion of stack clearing code into computer program source code located between said pair of enabling and disabling user compiler controls.

21. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 20, wherein said pair of enabling and disabling user compiler controls further comprises an enabling pragma control and a disabling pragma control.

22. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, wherein said user compiler control further comprises a global control which enable stack clearing code insertion for all computer program source code.

23. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, wherein said user compiler control is disposed within a computer-readable compiler control file.

24. A computer program product for producing computer executable code for automatically clearing a computer program stack in computer memory as set forth in claim 13, further comprising computer program means disposed in a computer usable medium for receiving said user compiler control via a compiler invocation command argument.

25. A system for producing computer executable code from computer source code, and for automatically including executable code which clears computer program stack used by called processes and subroutines, said program stack being operable for storing and passing of data between calling and called processes and subroutines, said system comprising:

a computer suitable for compiling computer source code, said computer having a processor and computer-readable memory;

a compiler control; and

a source code compiler disposed in a computer-readable memory and being executable by said computer, said source code compiler having an input for receiving computer source code to be compiled, and having an output for creating computer executable code, said source code compiler further having an analyzer for identifying program and subroutine call operations and return operations in computer source code, and having a code inserter which inserts program stack clearing code prior to return operations and following call operations in computer source code, said insertion being performed only if enabled by a compiler control.

26. A system for producing computer executable code from computer source code as set forth in claim 25, wherein said code inserter further comprises an inserter for code at a position within computer source code following a call operation to clear a return address value stored on the stack memory as a result of the call operation.

27. A system for producing computer executable code from computer source code as set forth in claim 25, wherein said code inserter further comprises an inserter for code at a position within computer source code following a call operation to clear processor context values stored on the stack memory as a result of the call operation.

28. A system for producing computer executable code from computer source code as set forth in claim 25, wherein said code inserter further comprises an inserter for code at a position within computer source code preceding a return operation to clear argument values passed to the called process by the calling process.

29. A system for producing computer executable code from computer source code as set forth in claim 25, wherein said code inserter further comprises an inserter for code at a position within computer source code preceding a return operation to clear local data values created by the called process.

30. A system for producing computer executable code from computer source code as set forth in claim 25, wherein said compiler control further comprises a pair of enable and disable commands which cause automatic insertion of stack clearing code into computer source code located between the enable and disable commands.

31. A system for producing computer executable code from computer source code as set forth in claim 25, wherein said pair of enable and disable commands comprises and enable pragma and a disable pragma.

32. A system for producing computer executable code from computer source code as set forth in claim 25, wherein said compiler control further comprises a global enable command which causes automatic insertion of stack clearing code into all computer source code compiled by the compiler.

33. A system for producing computer executable code from computer source code as set forth in claim 25, wherein said compiler control is disposed in a compiler control file embodied in a computer usable medium.

34. A system for producing computer executable code from computer source code as set forth in claim 25, further comprising a user input device through which said compiler control is specified.

35. A system for producing computer executable code from computer source code as set forth in claim 34, wherein said user input device further comprises a keyboard.

36. A system for producing computer executable code from computer source code as set forth in claim 34, where in said user input device further comprises a mouse.