US 6,553,429 B1 · Fast conditional thunk utility

Abstract

A conditional thunk utility employing an assembler-level direct-branch thunk technique. In a condition-check alternative, the conditional thunk utility performs a condition check followed by a direct-branch jump. The condition-check methodology is implemented using an assembler-level direct-branch technique, and the conditional thunk utility does not utilize the stack to queue the arguments of a function call. Thus, the stack is not altered from its desired condition just prior to executing the API function call. The condition-check alternative checks the thunk condition for each function call and, for this reason, may be used when the thunk condition can vary relatively frequently while the host computer system is running. In a jump-table alternative, the conditional thunk utility performs an assembler-level jump table check followed by a direct jump to a target address. In the jump-table alternative, the assembler-level direct branch code is configured to retrieve the jump address for the conditional thunk decision from the instruction cache memory (I-cache). Because the thunk conditions are checked and the jump table is configured in advance, the jump-table embodiment does not require a thunk condition check before each jump. For this reason, the jump-table alternative may be used for thunk conditions are invariant, or vary relatively infrequently, while the host computer system is running.

Claims11

Dependent claims

A computer-readable medium having computer-executable instructions for performing the steps of:

checking a plurality of thunk conditions to obtain a thunk condition result for each of a plurality of functions;
loading an assembler-level jump table with a target address for each function, the value of the target address for each function depending on the thunk condition result for that function;
generating a function call associated with a conditionally thunked function;
pushing parameters associated with the function call onto a parameter passing utility associated with a computer system;
without altering the condition of the parameter passing utility, invoking an assembler-level direct-branch conditional thunk utility configured for selecting a version of the function based on a condition of the computer system;
calling the selected version of the function;
reading the parameters from the parameter passing utility;
and
performing the selected version of the function using the parameters read from the parameter passing utility.

6 more elements

A computer-readable medium having computer-executable instructions for performing the steps of:

checking a plurality of thunk conditions to obtain a thunk condition result for each of a plurality of conditionally thunked functions, and
loading an assembler-level jump table with a target address for each function, the value of the target address depending on the thunk condition result the associated function;
generating a function call associated with one of the functions;
pushing parameters associated with the function call onto a parameter passing utility;
without altering the condition of the parameter passing utility, invoking an assembler-level direct-branch conditional thunk utility configured for jumping to a previously-selected version of the function based on a condition of a computer system by,
obtaining a target address associated with the function from an assembler-level jump table, and
jumping to the target address;
calling the previously-selected version of the function located at the target address;
reading the parameters from the parameter passing utility;
and
performing the selected version of the function using the parameters read from the parameter passing utility.

8 more elements

Dependencies are inferred from the claim text.

Fast conditional thunk utility

Life of this patent

Fast conditional thunk utility

Life of this patent

Abstract

Claims11