초록 ▼

A data storage resource is identifiable by physical addresses, and optionally by a virtual address. A policy defines which resources are accessible and which resources are not accessible. A request to access a resource is allowed if access to the resource is permitted by the policy, and if carrying

A data storage resource is identifiable by physical addresses, and optionally by a virtual address. A policy defines which resources are accessible and which resources are not accessible. A request to access a resource is allowed if access to the resource is permitted by the policy, and if carrying out the access will not cause virtual addresses to be assigned to resources to which the policy disallows access. Since resources to which access is disallowed do not have virtual addresses, certain types of access requests that identify a resource by a virtual address can be allowed without consulting the policy.

대표청구항 ▼

What is claimed is: 1. A method of controlling access to a plurality of resources in accordance with a policy, each of the resources being addressable by a set of first identifiers, at least some of the resources being addressable by a set of second identifiers, the method comprising: initializing

What is claimed is: 1. A method of controlling access to a plurality of resources in accordance with a policy, each of the resources being addressable by a set of first identifiers, at least some of the resources being addressable by a set of second identifiers, the method comprising: initializing the resources to a state that does not include any of the resources that a source is not allowed to access under the policy and are not addressable by the source with any of the second identifiers; receiving a request to access one of the resources, the request identifying said one of the resources by one of the second identifiers; determining whether said request is a read request for one of the resources identified by one of the second identifiers; and allowing the request without further evaluation of whether said request is allowable under said policy if, based on the determination, the read request references resources that are included in a list of addressable resources, wherein the request is denied when the request references a first identifier that is determined to be outside of the list of addressable resources. 2. The method of claim 1, wherein the first identifiers are physical addresses of the resources, wherein the second identifiers are virtual addresses, and wherein a modifiable mapping maps at least some of the virtual addresses to at least some of the physical addresses. 3. The method of claim 2, wherein said mapping is based at least in part on the identity of a source that issues said request. 4. The method of claim 3, wherein said mapping is further based on information other than the second identifiers and the identity of the source that issues said request. 5. The method of claim 1, wherein the act of initializing the resources comprises: initializing the resource to a state in which none of the resources that the source is not allowed to write under the policy is addressable by the source with any of the second identifiers. 6. The method of claim 1, wherein information that affects which of the resources corresponds to a given virtual address is stored in a first set of the resources, and wherein the act of initializing the resources comprises: initializing the resources to a state in which none of the resources that the source is not allowed to access under the policy are in the first set. 7. The method of claim 1, wherein information that affects which of the resources corresponds to a given virtual address is stored in a first set of the resources, and wherein the act of initializing the resources comprises: initializing the resources to a state in which none of the resources that a source is not allowed to write under the policy is addressable by the source with any of the second identifiers, and in which none of the resources that the source is not allowed to write under the policy are in the first set. 8. A computer-readable medium encoded with computer-executable instructions to perform a method of controlling access to a plurality of resources according to a policy in a system comprising a first set of resources, each of the set of resources being addressable by a set of first identifiers, at least some of the resources being addressable by a set of second identifiers, each of the second identifiers having an attribute associated therewith indicating whether a resource identified by a second identifier is read-only, information affecting which of the resources corresponds to a given virtual address being stored in a set of the resources, the method comprising: initializing the resources to a state that does not include any of the resources that a source is not allowed to access under the policy and are not addressable by the source with any of the second identifiers, and in which the set of resources does not include any resource whose second identifier is associated with an attribute indicative of being only readable by the source; receiving a request to access one of the resources, the request identifying said one of the resources by one of the second identifiers; determining whether said request is a write request for one of the resources identified by one of the second identifiers; and allowing the request without further evaluating whether said request is allowable under said policy if, based on the determination, the write request references resources that are included in a list of addressable resources, wherein the request is denied when the request references a first identifier that is determined to be outside of the list of addressable resources. 9. The computer-readable medium of claim 8, wherein the method further comprises: initializing the resources to a state in which none of the resources that a source is not allowed to write under the policy is addressable by the source with any of the second identifiers. 10. In a system that comprises a plurality of resources and a virtual memory manager, each of the resources being addressable by a physical address, the virtual memory manager enabling at least some of the resources to be addressable by virtual addresses, a process comprising: invoking a guard that evaluates a request to allow a source to access at least one of the resources; the guard determining whether said request is a read request that uses a virtual address to identify the resource, where if, based on the determination, the request is the read request, the guard allowing the request; and wherein, if based on the determination, the request comprises a write request component, the guard allowing access to said one of the resources if a group of one or more conditions is true, the guard otherwise denying the request, the conditions comprising: the request being allowable under a policy; and execution of the request will not result in the creation of a circumstance in which any of the resources that the source is not allowed to access under the policy become addressable by the source with a virtual address. 11. The improvement of claim 10, wherein the system has been initialized to a state in which none of the resources that the source is allowed to access under the policy are addressable by the source with virtual addresses. 12. The improvement of claim 10, wherein information affecting which of the resources are associated with virtual addresses is sorted in a set of the resources, and wherein the conditions further comprise: execution of the request not resulting in a circumstance in which the set includes resources that the source is not allowed to access under the policy. 13. The improvement of claim 10, wherein the conditions further comprise: execution of the request not resulting in a circumstance in which any of the resources that the source is not allowed to write under the policy are addressable by the source with a virtual address. 14. The improvement of claim 13, wherein information affecting which of the resources are associated with virtual addresses is stored in a set of the resources, and wherein the conditions further comprise: execution of the request not resulting in a circumstance in which the set includes resources that the source is not allowed to write under the policy. 15. The improvement of claim 10, wherein the system further comprises a processor, and wherein the guard comprises executable instructions that execute on the processor. 16. The improvement of claim 10, wherein the guard comprises at least one of: hardware logic and firmware. 17. The improvement of claim 10, wherein the virtual memory manager associates an attribute with a resource that has been requested by a virtual address, the attribute indicating whether the resource may be only written or read and written, the virtual memory manager being configured to invoke said guard when a request is received to write to a resource whose corresponding attribute indicates that the resource is only readable. 18. The improvement of claim 17, wherein the virtual memory manager raises an exception whenever a request is received to write to a resource whose corresponding attribute indicates that the resource is only readable, and wherein the guard comprises, or is invoked by, a handler for said exception. 19. The improvement of claim 17, wherein information affecting which of the resources are associated with virtual addresses is stored in a set of the resources, each of the resources in the set being associated with an attribute indicating that the resource is only readable when requested by said source. 20. The improvement of claim 10, wherein the virtual memory manager indicates, for each resource requestable by virtual address, whether the resource is present or not present, the virtual memory manager being configured to invoke said guard when a request is received to access a resource that is indicted as not present, and wherein the virtual memory manager is configured to invoke said guard when a request is received to access a resource whose corresponding attribute indicates that the resource is not present.