US 4,366,537 AGranted

Authorization mechanism for transfer of program control or data between different address spaces having different storage protect keys

AssigneeInternational Business Machines Corporation

InventorsAndrew R. Heller, William S. Worley, Jr.

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Abstract

Permits one program in one address space to obtain access to data in another address space or to call a program in another address space without invoking a supervisor, with authorization to use a storage protect key other than that specifically assigned to the program by a supervisor when in a new semi-privileged state. Programs executing in a particular address space have supervisor assigned storage protect key masks permitting the program, when authorized, to utilize a storage protect key other than the one specifically assigned by the supervisor. A second address space can be designated by a program, and when authorized, can cause transfer of data in main memory from one physical location to another associated with the different address space, and two different storage protect keys can be utilized. A calling program can provide addressability to data in its address space by combining storage protect key masks from the calling program with a key mask of a called program to permit access to data by the called program. Entering the called program causes the saving and changing of a problem/supervisor control bit and instruction address.

Claims8

Dependent claims

In a multiprogramming data processing system including (1) a main memory comprised of an addressing mechanism providing access to physical, addressable blocks having associated addressable coded storage protect keys providing access control to the associated physical block, the main memory storing information including data, problem programs, supervisor programs, and system control tables, and (2) processor means for extracting and decoding series of program instructions from the main memory and for performing the operations required including the accessing of physical addressable blocks in the main memory for transfer of information between the processor and main memory, the processor including a program status word (PSW) register including a plurality of control bits including a problem program bit, the binary state of which signifies a problem or supervisor program state, control fields including a coded PSW protect key field connected to the access control of the main memory to be compared with the coded storage protect key of a physical block to be accessed in main memory, and an instruction address field connected to the addressing mechanism of the main memory for accessing the next program instruction to be executed, the improvement comprising:

key-mask storage comprised of a plurality of binary key-mask bits, each corresponding to a different one of the permutations of the coded storage protect keys in the PSW protect key field and storage protect keys, and each having a first or second binary state,
program call signalling means, responsive to a program instruction, from a calling program, providing a called program identification,
entry access means responsive to said called program identification, including means for accessing a particular entry in an associated system control table for transferring said particular entry to the processor, and means for storing said particular entry which comprises entry control information including an initial called program instruction address, and an authorization key-mask having the same plurality of binary key-mask bits as said key-mask storage, and
key-mask checking means, connected to said key-mask storage and said authorization key-mask, including means for performing a bit-for-bit combinatorial function and providing an interrupt signal in response to a particular result of said combinatorial function.

1 more element

key-mask storage comprised of a plurality of binary key-mask bits, each corresponding to a different one of the permutations of the coded storage protect keys in the PSW protect key field and storage protect keys, and each having a first or second binary state,
key authorization checking means, operative when the PSW problem bit indicates the processor is in the problem program state, including check initiating signalling means indicating a requirement of a problem program operation to obtain authority for the use of at least one coded storage protect key different from the PSW protect key, and
inhibit means, connected to said PSW problem program bit and said key-mask bit in said key-mask storage corresponding to said at least one coded storage protect key, for preventing the problem program operation when said key-mask bit is in said second binary state.

Dependencies are inferred from the claim text.