Dynamic Translation in the Presence of Intermixed Code and Data

• US 20100287355A1
• Filed: 05/05/2009
• Published: 11/11/2010
• Est. Priority Date: 05/05/2009
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Nair, Ravi, Stoodley, Kevin A.
• Granted Patent: US 8,103,850 B2
• Time in Patent Office: Days
• US Class Current: 711/207
• CPC Class Codes: G06F 12/1027 using associative or pseudo-associative address translation means, e.g. translation look-aside buffer [TLB]
• CPC Class Codes: G06F 2212/655 Same page detection
• CPC Class Codes: G06F 9/45516 Runtime code conversion or optimisation

Abstract

A system for translating software in a first format into a second format includes a memory containing the software in the first format and an emulator coupled to the memory configured to translate the software from the first format to the second format. The system also includes a host engine coupled to the emulator and configured to perform instructions in the second format. The emulator is configured to determine whether a store command in the first format stores information to a memory page that includes instructions and to convert the store instruction to a special store instruction in the event that the target of the store instruction does not contain an instruction.

Claims

1. A system for translating software in a first format into a second format, the system comprising:

a memory containing the software in the first format;

an emulator coupled to the memory configured to translate the software from the first format to the second format; and

a host engine coupled to the emulator and configured to perform instructions in the second format;

wherein the emulator is configured to determine whether a store command in the first format stores information to a memory page that includes instructions and to convert the store instruction to a special store instruction in the event that the target of the store instruction does not contain an instruction.

2. The system of claim 1, further comprising:

a translation lookaside buffer containing translations from virtual memory addresses to physical memory addresses;

a code table listing addresses of regions in the memory containing code previously translated from the first format to the second format.

3. The system of claim 2, wherein the code table further comprises:

code lookaside buffer containing translations from the first format to the second; and

a translation cross-reference table containing entries pointing to translated code that may exist for any location that is a target of a store instruction.

4. The system of claim 3, wherein the emulator is configured to determine, for each store command, whether the target address of the translation is located on a page that contains code.

5. The system of claim 4, wherein the emulator is further configured to access the translation cross-reference table in the event that the target address of the translation is located on a page that contains code and to determine if the target address includes an instruction.

6. A method for translating code from a first format to a second format, the method comprising:

receiving a section of code to be translated from the first format to the second format;

determining that a particular instruction is a store instruction;

accessing a translation lookaside buffer to determine that the address of the store is present;

determining that the store instruction accesses a memory page that includes instructions;

generating a code alias trap;

accessing a translation cross-reference table and determining that the address contains data and not instructions; and

updating the translation for the store instruction to a special store instruction.

7. The method of claim 6, further comprising:

invalidating the translation for the store instruction in a code table.

8. The method of claim 6, further comprising:

determining that the store instruction is a special store instruction; and

executing the special store instruction without generating a code trap.

9. The method of claim 8, wherein the special store instruction is an instruction to store a half-word.

10. The method of claim 8, wherein the special store instruction is an instruction to store a word.

11. The method of claim 8, wherein the special store instruction is an instruction to store a double word.

12. The method of claim 6, further comprising:

accessing the translation lookaside buffer to determine that the address of the store is not present; and

updating the translation lookaside buffer to include the address.

13. The method of claim 6, further comprising:

accessing the code lookaside buffer to determine that the address of the store is not present; and

updating the code lookaside buffer to include the address.

14. A system for translating software in a first format into a second format, the system comprising:

a memory containing the software in the first format;

an emulator coupled to the memory configured to translate the software from the first format to the second format; and

a host engine coupled to the emulator and configured to perform instructions in the second format;

wherein the emulator is configured to speculatively use store commands in the first format, maintaining a table of such stores created and the destination addresses of such stores and convert them to special store commands in the second format in the event that subsequent execution branches to the location which is the destination of the store command with this replacement being performed before execution of the code at said destination location.