Google Inc.

Sriraman Tallam

Xinliang David Li

Cary Allen Coutant

Christopher G Demetriou

Ian Lance Taylor

Geoffrey Roeder Pike

Úlfar Erlingsson

Lawrence Alan Crowl

Caroline Tice

Kenneth Buchanan

Paul Pluzhnikov

Methods for reducing memory loads for accessing global variables (globals) when creating executables for position independent (PI) code are disclosed. A first method includes compiling PI code, identifying globals, and determining whether globals are defined in the executable. If a global is not defined in the executable, a definition is created in the executable. A second method includes receiving a list of defined globals from instrumented PI code binary and comparing the list with globals in the PI code. Memory loads are created for globals that are unlisted. A third method includes compiling PI code with special relocations for globals and determining whether globals are defined in the executable. If the global is defined in the executable, the special relocation is replaced with a direct load of the global. If not, the special relocation is replaced with a two-instruction sequence that loads the global's address and then the global's value.

Methods to eliminate extra memory loads while accessing global variables in position independent code

A system and method for detecting execution of unsupported instructions while testing multiversioned functions within software application code are disclosed. An example method includes annotating a software application's executable binary to distinguish functions that are directed to particular hardware variations. Functions with instructions that are unsupported by a simulated hardware platform variation on which the software application's annotated executable binary will run may then be detected. The contents of the detected functions may be rewritten with trap instructions. At runtime, when executing the software application on the simulated hardware platform variation running on a different physical hardware platform variation, responsive to execution of a function with instructions that are unsupported by the simulated hardware platform, terminating the software application based on the execution of the trap instructions. Execution of unsupported instructions may be detected based on the termination of the software application.

Method and apparatus for detecting execution of unsupported instructions while testing multiversioned code

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for receiving source code that contains a hot function that calls a multiversioned function, where a function definition of the multiversioned function specifies a first version and an alternative second version, and generating compiled code that includes a first and a second clone of the hot function, and a first and a second version of the multiversioned function. In the compiled code, the first clone of the hot function includes a direct call to the first version of the multiversioned function, and the second clone of the hot function includes a direct call to the second version of the multiversioned function.

Multiversioned functions

A system and method is disclosed for providing security in virtual function calling. During a build process a program code is analyzed to identify one or more call sites used to facilitate a call to a subroutine associated with a declared object type. One or more trusted vtable pointers to a respective subroutine is determined, and the program is configured, via the build process, to detect, at an execution time, an initiation of a virtual call at a call site, verify whether a vtable pointer used in connection with the call site is associated with at least one of the trusted vtable pointers, and, if verified, facilitate the virtual call using the call site. If the vtable pointer cannot be verified then the virtual call is aborted.

Detecting and handling vtable pointer corruption

A system and method for optimizing the object codes of a computer program is disclosed. The method includes receiving one or more object code units associated with an executable program; identifying, among the object code units, a first program entity and a first set of operations associated with the first program entity and a second program entity and a second set of operations associated with the second program entity, each program entity having an object code segment and an associated address; updating the object code units by inserting a predefined instruction before the first program entity's object code segment and causing the second set of operations to be associated with the predefined instruction if the first program entity's object code segment is identical to the second program entity's object code segment; and combining the updated object code units into the executable program.

Method and system for optimizing an executable program by generating special operations for identical program entities

A system and method for optimizing the object code of a computer program is disclosed. The method includes receiving one or more object code units from the memory; identifying first and second identical program entities in the one or more object code units, wherein each program entity has an object code segment and an associated address; updating the one or more object code units by merging the first identical program entity with the second identical program entity if neither of the first and second program entities is subject to an operation on the respective program entity's address; and linking the updated one or more object code units into an executable program.

Growing community of inventors

Sunnyvale, CA, United States of America

Sriraman Tallam