Patching functions in use on a running computer system

• US 10,310,863 B1
• Filed: 07/31/2013
• Issued: 06/04/2019
• Est. Priority Date: 07/31/2013
• Status: Active Grant

• Current Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Original Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Inventors: Poimboeuf, Joshua Nathan, Rostedt, Steven David
• Primary Examiner(s): Mitchell, Jason D
• Application Number:
  US13/955,937
• Time in Patent Office: 2,134 Days
• Field of Search: 717168-173, 717127-130
• 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 8/656 while running

Abstract

A mechanism for patching functions in use on a running computer system. A method includes modifying an original function to call a hot patch function. The hot patch function transfers execution control from the original function to a replacement function.

Claims

1. A method comprising:

receiving a call to an original function;

modifying, by a processing device, the original function to call a hot patch function to transfer execution control from the original function to a replacement function by changing an initial instruction in the original function that specifies no operation to be executed to specifying that the call to the hot patch function is to be executed, wherein the hot patch function is conditionally applied to replace the original function in view of a number of calls to the original function that have been received by applying the hot patch function for a particular call for every defined number of calls that have been received and not applying the hot patch function for remaining calls for every defined number of calls that have been received;

changing, by the processing device, a value of a pointer, in a data structure identifying a plurality of original functions used by an operating system, from an original memory location associated with the original function to a replacement memory location associated with the replacement function;

executing, by the processing device, the replacement function using the pointer to the replacement memory location associated with the replacement function in the data structure identifying the plurality of original functions used by the operating system; and

returning, by the processing device, to a caller of the original function in response to executing the replacement function.

2. The method of claim 1 wherein the hot patch function is associated with a security update for the original function.

3. The method of claim 1, further comprising:

in response to executing the replacement function, changing a value of a register of the processing device to reflect another value of the original function, wherein the executing of the replacement function uses the another value of the original function.

4. The method of claim 3 further comprising calling the original function to execute the changed first instruction of the original function.

5. The method of claim 1, wherein the transferring execution control comprises returning from the hot patch function to the replacement function.

6. The method of claim 1 wherein the original function is modified during run time of the operating system.

7. A system comprising:

a memory;

a processing device, operatively coupled with the memory, to;

receive a call to an original function;

modify the original function to call a hot patch function to transfer execution control from the original function to a replacement function by changing an initial instruction in the original function that specifies no operation to be executed to specifying that the call to the hot patch function is to be executed, wherein the hot patch function is conditionally applied to replace the original function in view of a number of calls to the original function that have been received by applying the hot patch function for a particular call for every defined number of calls that have been received and not applying the hot patch function for remaining calls for every defined number of calls that have been received;

change a value of a pointer, in a data structure identifying a plurality of original functions used by an operating system, from an original memory location associated with the original function to a replacement memory location associated with the replacement function;

execute the replacement function using the pointer to the replacement memory location associated with the replacement function in the data structure identifying the plurality of original functions used by the operating system; and

return to a caller of the original function in response to executing the replacement function.

8. The system of claim 7, wherein the hot patch function is associated with a security update for the original function.

9. The system of claim 7, wherein the processing device is further to:

in response to executing the replacement function, change a value of a register of the processing device to reflect another value of the original function, wherein the executing of the replacement function uses the another value of the original function.

10. The system of claim 9, the processing device to call the original function to execute the changed first instruction of the original function.

11. The system of claim 7, wherein to transfer execution control, the processing device is to return from the hot patch function to the replacement function.

12. The system of claim 7, wherein the original function is modified during run time of the operating system.

13. A non-transitory machine-readable storage medium comprising data, when accessed by a processing device, cause the processing device to:

receive a call to an original function;

modify, by the processing device, the original function to call a hot patch function to transfer execution control from the original function to a replacement function by changing an initial instruction in the original function that specifies no operation to be executed to specifying that the call to the hot patch function is to be executed, wherein the hot patch function is conditionally applied to replace the original function in view of a number of calls to the original function that have been received by applying the hot patch function for a particular call for every defined number of calls that have been received and not applying the hot patch function for remaining calls for every defined number of calls that have been received;

change, by the processing device, a value of a pointer, in a data structure identifying a plurality of original functions used by an operating system, from an original memory location associated with the original function to a replacement memory location associated with the replacement function;

execute, by the processing device, the replacement function using the pointer to the replacement memory location associated with the replacement function in the data structure identifying the plurality of original functions used by the operating system; and

return, by the processing device, to a caller of the original function in response to executing the replacement function.

14. The non-transitory machine-readable storage medium of claim 13, wherein the hot patch function is associated with a security update for the original function.

15. The non-transitory machine-readable storage medium of claim 13, wherein the processing device is further to:

in response to executing the replacement function, change a value of a register of the processing device to reflect another value of the original function, wherein the executing of the replacement function uses the another value of the original function.

16. The non-transitory machine-readable storage medium of claim 13, wherein the processing device is to call the original function to execute the changed first instruction of the original function.

17. The non-transitory machine-readable storage medium of claim 14 wherein the first instruction is a no-op instruction.