Mechanism for lossless tracing in an arbitrary context

1. A method for tracing an instrumented program, comprising:

triggering a probe in the instrumented program;

obtaining an original instruction associated with the probe, wherein obtaining the original instruction comprises searching a look-up table using a program counter value, wherein the look-up table comprises the original instruction associated with the probe and an address associated with the original instruction;

loading the original instruction into a scratch space, wherein the scratch space is allocated on a per-thread basis; and

executing the original instruction in the scratch space using a thread, wherein executing the original instruction results in placing the instrumented program in a state equivalent to natively executing the original instruction.

2. The method of claim 1 , further comprising:

emulating a location dependent instruction to determine a value of a program counter if the original instruction is a control-flow instruction wherein semantics of the location dependent instruction depend on a location of the original instruction within the instrumented program.

3. The method of claim 1 , further comprising:

incrementing a value of a program counter using a size of the original instruction.

4. The method of claim 1 , further comprising:

determining a value of a program counter; and

loading the value of the program counter into the scratch space.

5. The method of claim 4 , wherein determining the value of the program counter comprises:

incrementing the value of the program counter using a size of the original instruction if the original instruction is not a control-flow instruction; and

emulating a location dependent instruction to determine the value of the program counter if the original instruction is a control-flow instruction.

6. The method of claim 1 , furthering comprising:

loading a control transfer instruction into the scratch space prior to executing the original instruction.

7. The method of claim 6 , wherein the control transfer instruction includes a value of a program counter.

8. The method of claim 1 , wherein the probe corresponds to a trap.

9. The method of claim 1 , wherein the instrumented program is executed on multi-thread architecture.

10. The method of claim 1 , wherein executing the original instruction comprises single-stepping the original instruction.

11. The method of claim 1 , wherein executing the original instruction comprises single-stepping the original instruction.

12. A system for tracing an instrumented program, comprising:

a thread configured to execute the instrumented program;

a look-up table arranged to store an address and a corresponding original instruction;

a trap handler configured to halt execution of the thread when a trap instruction is encountered and using an address of the trap instruction to obtain the corresponding original instruction from the look-up table;

a scratch space arranged to store the original instruction, wherein the scratch space is allocated on a per-thread basis; and

an execution facility for executing the original instruction in the scratch space to obtain data.

13. The system of claim 12 , further comprising:

a buffer for storing the data.

14. The system of claim 12 , further comprising:

a tracing framework emulating a location dependent instruction to determine a value of a program counter if the original instruction is a control-flow instruction.

15. The system to claim 12 , wherein the trap handler sets the value of the program counter to the value of a next address immediately the address of the trap instruction after executing the original instruction.

16. The system of claim 12 , wherein the trap handler increments a value of a program counter using a size of the original instruction if the original instruction is not a control-flow instruction.

17. The system of claim 12 , wherein the instrumented program is executed on multi-thread architecture.