US 5,335,334 AGranted

Data processing apparatus having a real memory region with a corresponding fixed memory protection key value and method for allocating memories therefor

AssigneeHitachi, Ltd.

InventorsKikuo Takahashi, Toyohiko Kagimasa, Toshiaki Mori

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Abstract

A region comprising a plurality of real pages in a part of a real storage unit is provided with a first key storage unit having a plurality of key storage entries each corresponding to one of the plurality of real pages, while a second region comprising a plurality of real pages in the second part of the real storage unit is provided with a second key storage unit having a single key storage entry. When a real address designated by an instruction to be executed belongs to the first region, an entry corresponding to this address is accessed by a storage protection control circuit. When this address belongs to the second region, the second key storage unit is accessed irrespective of the address. Further, a key within the accessed key information is compared with a key on a program status word (PSW) allocated to a program to determine whether the execution of the instruction is permitted.

Claims18

Dependent claims

A data processing apparatus comprising:

a real storage having first and second regions each having a plurality of real unit regions;
and
a plurality of storage locations, each storage location being provided for a corresponding one of said real unit regions of said first region, each of said plurality of storage locations having a first field for storing a storage protection key determined by a protection key assigned to a virtual unit region after a real unit region has been allocated to said virtual unit region and a second field for storing at least one information signal related to accessing said corresponding real unit region executed after said corresponding real unit region has been allocated to said virtual unit region,
one storage location provided in common to said plurality of real unit regions of said second region having a field for storing a storage protection key predetermined for common use among said real unit regions of said second region, said one storage location storing said predetermined storage protection key before one of said real unit regions of said second region is allocated to a virtual unit region;
and
accessing means responsive to an instruction designating one real unit region of said real storage for either of access to data held in said designated real unit region or access to a storage protection key for said one designated real unit region for accessing one of said plurality of storage locations corresponding to one of said real unit regions of said first region when the designated real unit region is one of said real unit regions of said first region, and for accessing said one storage location when the designated real unit region one of said real unit regions of said second region.

3 more elements

A data processing apparatus comprising:

a real storage having first and second regions each having a plurality of real unit regions;
a plurality of storage locations, each storage location being provided for a corresponding one of said real unit regions of said first region, and receiving a storage protection key determined by a protection key assigned to a virtual unit region after a real unit region corresponding to each of said storage locations of said first region has been allocated to said virtual unit region,
a single storage location provided in correspondence to said real unit regions of said second region for receiving a single storage protection key predetermined for said real unit regions of said second region prior to allocation of a real unit region of said second region to a virtual unit region;
and
determining means for determining whether access requested by a presently executed program to a specific one of said real unit regions of said first region is permissible based upon a storage protection key held in one of said plurality of storage locations corresponding to said specific real unit region of said first region, and for determining whether access requested by a presently executed program to one of said real unit regions of said second region is permissible based upon said predetermined single storage protection key.

2 more elements

In a data processing apparatus comprising a real storage having first and second regions each including a plurality of real unit regions, a plurality of storage locations, each storage location being provided for a corresponding one of said real unit regions of said first region, and a single storage location provided commonly for said real unit regions of said second region, a memory allocating method comprising the steps of:

(a) storing a predetermined storage protection key for said second region in said single storage location before allocating any of said real unit regions of said second region to a virtual unit region;
(b) determining whether or not a value of a storage protection key requested by a presently executed program for a virtual unit region is equal to said predetermined storage protection key in response to said presently executed program requesting allocation of a real unit region either of said first and second regions to said virtual unit region;
(c) allocating one of said real unit regions within said first region to said virtual unit region when a result of the determining step is negative;
(d) writing said storage protection key requested by the program for said virtual unit region into one of the plurality of storage locations corresponding to said allocated real unit region;
and
(e) allocating one of said real unit regions within said second region to said virtual real unit region when said result of the determining step is affirmative.

3 more elements

Dependencies are inferred from the claim text.