Protecting memory by containing pointer accesses

• US 7,761,676 B2
• Filed: 12/12/2006
• Issued: 07/20/2010
• Est. Priority Date: 12/12/2006
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Doshi, Kshitij A., Jacobson, Quinn A.
• Primary Examiner(s): Chace, Christian P
• Assistant Examiner(s): Otto, Alan
• Application Number:
  US11/637,661
• Publication Number:
  US 20080140968A1
• Time in Patent Office: 1,316 Days
• Field of Search: None
• US Class Current: 711/163
• CPC Class Codes: G06F 12/1466 Key-lock mechanism

Abstract

In one embodiment, the present invention includes a method for associating a first identifier with a first pointer that points to a first object in a memory. The first identifier may correspond to a value in a segment of a map array for a location of the first object in the memory. Other embodiments are described and claimed.

Claims

1. An apparatus comprising:

a computer-readable medium including instructions that enable the apparatus to organize a map including a plurality of elements each to store a value for a corresponding block of a memory, wherein the value is a random value to be arbitrarily generated and is to be used to determine access permission to the corresponding block of the memory, wherein access to a kth portion of the memory block is to be controlled by comparison of a value of the element of a location of the map that is k locations from the location of the map for the memory block, and wherein the instructions enable accessing a vector associated with at least one of the elements of the map, wherein the vector includes a plurality of portions each having a first value to identify that a corresponding portion of the corresponding block of the memory includes an object boundary, and having a second value to identify that the corresponding portion does not include an object boundary.

2. The apparatus of claim 1, further comprising a storage to store at least a portion of the map, wherein the portion is to accelerate determination of the access permission.

3. The apparatus of claim 2, wherein the storage comprises a color lookaside buffer (CLB).

4. The apparatus of claim 3, wherein the CLB is to store a plurality of entries, each of the entries to include a portion of the map for a region of the memory including a plurality of blocks.

5. The apparatus of claim 3, further comprising a translation lookaside buffer (TLB) to store virtual address to physical address translations.

6. The apparatus of claim 5, wherein the CLB is to be maintained incoherently with the TLB.

7. The apparatus of claim 1, wherein the map is to store a first selected value in an element if access to the corresponding block of the memory is to be unlimited such that a pointer having an encoding portion with any value can access the memory block, and to store a second selected value in the element if no access to the corresponding block of the memory is to be permitted such that no pointer can access the memory block.

8. The apparatus of claim 1, further comprising an access validator to determine if an identifier portion of a pointer matches the value stored in an element of the map, wherein the pointer points to a block of the memory corresponding to the element of the map.

9. The apparatus of claim 8, wherein the access validator is to prevent access to the corresponding block of the memory if a mismatch occurs.

18. The apparatus of claim 1, wherein the random value is to be reused according to random scheme to determine access permission to a different block of the memory.

10. A machine-readable medium having stored thereon instructions, which if executed by a machine cause the machine to perform a method comprising:

determining if a first portion of a pointer matches a value stored in a location of a map that corresponds to a block of memory pointed to by the pointer when executing a first program on the machine, the value corresponding to a random value arbitrarily generated to provide statistical protection against type-unsafe pointer accesses; and

allowing access to the block of memory if a match occurs, otherwise preventing the access, wherein access to a kth portion of the memory block is to be controlled by comparison of a value of a location of the map that is k locations from the location of the map for the memory block; and

accessing a vector associated with at least one of the locations of the map, wherein the vector includes a plurality of portions each having a first value to identify that a corresponding portion of the corresponding block of the memory includes an object boundary, and having a second value to identify that the corresponding portion does not include an object boundary.

11. The machine-readable medium of claim 10, wherein the method further comprises:

searching a color lookaside buffer (CLB) for a portion of the map associated with the pointer; and

obtaining and storing the portion of the map in the CLB if the portion of the map is not present in the CLB.

12. The machine-readable medium of claim 10, wherein the method further comprises encoding the value in an instruction that is to access the block of memory.

13. The machine-readable medium of claim 10, wherein the method further comprises dynamically modifying a size of the location of the map and the corresponding block of memory.

19. The machine-readable medium of claim 10, wherein the method further comprises not determining if the first portion of the pointer matches the value and instead directly allowing the access to the memory block when executing a second program on the machine, the second program corresponding to a legacy program unaware of the statistical protection.

14. A system comprising:

a map having a plurality of locations each to store an identifier to control access to a corresponding block of a memory, wherein access to a k^th portion of the memory block is to be controlled by comparison of a value of the identifier of a location of the map that is k locations from the location of the map for the memory block;

a vector associated with at least one of the locations of the map, wherein the vector includes a plurality of portions each having a first value to identify that a corresponding portion of the corresponding block of the memory includes an object boundary, and having a second value to identify that the corresponding portion does not include an object boundary; and

a dynamic random access memory (DRAM) coupled to the map, the DRAM comprising the memory.

15. The system of claim 14, further comprising a color lookaside buffer (CLB) to store a plurality of entries, each of the entries to include a portion of the map for a region of the memory including a plurality of blocks.

16. The system of claim 15, further comprising a walker coupled to the CLB to obtain a portion of the map and store the portion in the CLB if at least a portion of a pointer does not hit in the CLB.

17. The system of claim 14, further comprising a control register to store a base address for the map.

20. The system of claim 14, wherein k is determined based on a number of the portions of the vector having a first value.

21. The system of claim 14, wherein k is determined based on a modulo operation between an address portion of a pointer to the corresponding portion of the memory block and a size of the memory block.

22. A processor comprising:

an execution unit to execute instructions; and

a memory management unit (MMU) coupled to the execution unit, the MMU including;

a translation lookaside buffer (TLB) to store virtual address to physical address translations; and

a color lookaside buffer (CLB) including a plurality of entries, each of the entries to include a portion of a map for a region of a memory coupled to the processor, the region including a plurality of blocks, the map including a plurality of elements each to store a value for a corresponding block of the memory, wherein the value is a random value to be arbitrarily generated and used to determine access permission to provide statistical protection against type-unsafe pointer accesses by a pointer to the corresponding block of the memory; and

a vector associated with at least one of the elements of the map, wherein the vector includes a plurality of portions each having a first value to identify that a corresponding portion of the corresponding block of the memory includes an object boundary, and having a second value to identify that the corresponding portion does not include an object boundary;

wherein the processor is to determine if a first portion of the pointer matches a value stored in an entry of the CLB during execution of a first program, and allow access to the block of memory if a match occurs, otherwise to prevent the access, wherein access to a kth portion of the memory block is to be controlled by comparison of a value of the element of a location of the map that is k locations from the location of the map for the memory block.

23. The processor of claim 22, wherein the processor is to search the CLB for a portion of the map associated with the pointer, and obtain and store the portion of the map in the CLB if the portion of the map is not present in the CLB.

24. The processor of claim 22, wherein the CLB is to be maintained incoherently with the TLB.