DEBUGGING PROGRAM CODE AT INSTRUCTION LEVEL THROUGH EMULATION

• US 20190065347A1
• Filed: 08/25/2017
• Published: 02/28/2019
• Est. Priority Date: 08/25/2017
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: MOLA, Jordi
• Granted Patent: US 10,445,216 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 11/3636 by tracing the execution of the program
• CPC Class Codes: G06F 11/3644 by instrumenting at runtime
• CPC Class Codes: G06F 11/3652 in-circuit-emulation [ICE] arrangements
• CPC Class Codes: G06F 11/3664 Environments for testing or debugging software
• CPC Class Codes: G06F 8/70 Software maintenance or management

Abstract

Methods and systems are disclosed for debugging program code at instruction level by emulating an epilog. Issues with retrieving values that a caller function has stored in non-volatile registers before calling a callee function are addressed at the instruction code level by through emulation. The epilog of the callee function may be emulated after copying a computing environment of the target program code from a target system to an emulation system. When the debugged code does not include an epilog, values that a caller function stored before calling a callee function in non-volatile registers may be retrieved by emulating the calling function forward from the breakpoint.

Claims

1. A computer-implemented method for debugging executable code, the method comprising:

executing the executable code stopping execution of the executable code at a current function;

locating an instruction code segment of the current function;

emulating the instruction code segment;

after emulating the instruction code segment, retrieving at least one value of non-volatile registers for a caller function of the current function, wherein the instruction code segment modifies at least one value of non-volatile registers; and

providing the at least one value of a non-volatile registers for the caller function.

2. The computer-implemented method of claim 1, wherein the executable code is executed in a target system, and wherein the method further comprises:

specifying, a breakpoint in the current function;

copying a set of data related to executing the executable code on the target system to an emulation system; and

wherein the instruction code segment is executed by the emulation system.

3. The computer-implemented method of claim 2, further comprising:

determining a set functions in a hierarchy of caller functions based on the current function;

determining at a set of one or more instruction code segments from the set of functions;

iteratively emulating the one or more instruction code segments; and

based upon the iterative emulation, providing at least one additional value for one or more non-volatile registers.

4. The computer-implemented method of claim 1, wherein the instruction code segment is an epilog of the current function, wherein the epilog restores non-volatile registers for a caller function.

5. The computer-implemented method of claim 1, wherein the method further comprises:

identifying a call to a callee function by the current function; and

determining a return instruction code for the callee function as the instruction code; and

after emulating the instruction code segment, retrieving at least one value of non-volatile registers for the caller function of the current function.

6. The computer-implemented method of claim 5, wherein determining the return instruction code for the second function further comprises:

determining at least one code in the caller function, wherein the at least one code calls the second function;

based on the at least one code, determine one or more parameters stored in a memory stack before calling the second function; and

based on statistical information, remove the one or more parameters from the memory stack.

7. The computer-implemented method of claim 1, wherein the instruction code segment is at least in part a prolog of the break function in a reverse sequence of instructions.

8. The computer-implemented method of claim 1, wherein the instruction code segment is at least a part of the current function when the current function is a leaf function, and wherein the leaf function is a function without a call instruction to another function.

9. A computing device, comprising:

at least one processing unit; and

at least one memory storing computer executable instructions for debugging program code at instruction level, the instructions when executed by the at least one processing unit causing the computing device to;

execute the executable code

stop execution of the executable code at a current function;

locate an instruction code segment of the current function;

emulate the instruction code segment;

after emulating the instruction code segment, retrieve at least one value of non-volatile registers for a caller function of the current function, wherein the instruction code segment modifies at least one value for non-volatile registers; and

provide the at least one value of a non-volatile registers for the caller function.

10. The computing device of claim 9, wherein the at least one program code is executed on a first computer, the instructions further causing the computing device to:

specify, a breakpoint in the current function;

copy a set of data related to executing the executable code on the target system to an emulation system; and

wherein the instruction code segment is executed by the emulation system.

11. The computing device of claim 10, the instructions further causing the computing device to:

determine a set functions in a hierarchy of caller functions based on the current function;

determine at a set of one or more instruction code segments from the set of functions;

iteratively emulate the one or more instruction code segments; and

based upon the iterative emulation, provide at least one addition value for one or more non-volatile registers;

12. The computing device of claim 9, wherein the instruction code segment is an epilog of the current function, wherein the epilog restores non-volatile registers for a caller function.

13. The computing device of claim 9, wherein the instruction code segment is at least one program instruction code of the break function, the instructions further causing the computing device to:

identify a call to a callee function by the current function; and

determine a return instruction code for the callee function as the instruction code; and

after emulating the instruction code segment, retrieve at least one value of non-volatile registers for the caller function of the current function.

14. The computing device of claim 13, the instruction to determine the return instruction code for the second function further causing the computing device to:

determine at least one code in the caller function, wherein the at least one code calls the second function;

based on the at least one code, determine one or more parameters stored in a memory stack before calling the second function; and

based on statistical information, remove the one or more parameters from the memory stack.

15. The computing device of claim 9, wherein the instruction code segment is at least in part of a prolog of the break function in a reverse sequence of instructions.

16. A computer storage device storing computer executable instructions for debugging program code at instruction level, the instructions when executed by at least one processing unit, cause the at least one processing unit to:

execute the program code;

stop execution of the program code at a current function;

locate an instruction code segment of the current function;

emulate the instruction code segment;

after emulating the instruction code segment, retrieve at least one value of non-volatile registers for a caller function of the current function, wherein the instruction code segment modifies at least one value for non-volatile registers; and

provide the at least one value of a non-volatile registers for the caller function.

17. A computer storage device of claim 16, wherein the instructions further cause the computing device to:

specify, a breakpoint in the current function;

copy a set of data related to executing the executable code on the target system to an emulation system; and

wherein the instruction code segment is executed by the emulation system.

18. A computer storage device of claim 16, wherein the instruction code segment is an epilog of the current function, wherein the epilog restores non-volatile registers for a caller function.

19. A computer storage device of claim 16, wherein the instruction code segment is at least one program instruction code of the break function, the instructions further causing the computing device to:

identify a call to a callee function by the current function; and

determine a return instruction code for the callee function as the instruction code; and

after emulating the instruction code segment, retrieve at least one value of non-volatile registers for the caller function of the current function.

20. A computer storage device of claim 19, the instruction to determine the return instruction code for the second function further causing the computing device to:

determine at least one code in the caller function, wherein the at least one code calls the second function;

based on the at least one code, determine one or more parameters stored in a memory stack before calling the second function; and

based on statistical information, remove the one or more parameters from the memory stack.