Patent Publication Number: US-4731734-A

Title: Digital computer system incorporating object-based addressing and access control and tables defining derivation of addresses of data from operands in instructions

Description:
This is a continuation of application Ser. No. 542,088, filed Oct. 17, 1983, now abandoned, which is a continuation of application Ser. No. 266,410, filed May 22, 1981, now abandoned. 
    
    
     CROSS REFERENCE TO RELATED APPLICATIONS 
     The present patent application is related to U.S. patent application Ser. No. 266,426 now U.S. Pat. No. 4,575,797 assigned to the assignee of the present application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a digital data processing system and, more particularly, to a multiprocess digital data processing system suitable for use in a data processing network and having a simplified, flexible user interface and flexible, multileveled internal mechanisms. 
     2. Description of Prior Art 
     A general trend in the development of data processing systems has been towards systems suitable for use in interconnected data processing networks. Another trend has been towards data processing systems wherein the internal structure of the system is flexible, protected from users, and effectively invisible to the user and wherein the user is presented with a flexible and simplified interface to the system. 
     Certain problems and shortcomings affecting the realization of such a data processing system have appeared repeatedly in the prior art and must be overcome to create a data processing system having the above attributes. These prior art problems and limitations include the following topics. 
     First, the data processing systems of the prior art have not provided a system wide addressing system suitable for use in common by a large number of data processing systems interconnected into a network. Addressing systems of the prior art have not provided sufficiently large address spaces and have not allowed information to be permanently and uniquely identified. Prior addressing systems have not made provisions for information to be located and identified as to type or format, and have not provided sufficient granularity. In addition, prior addressing systems have reflected the physical structure of particular data processing systems. That is, the addressing systems have been dependent upon whether a particular computer was, for example, an 8, 16, 32, 64 or 128 bit machine. Since prior data processing systems have incorporated addressing mechanisms wherein the actual physical structureof the processing system is apparent to the user, the operations a user could perform have been limited by the addressing mechanisms. In addition, prior processor systems have operated as fixed word length machines, further limiting user operations. 
     Prior data processing systems have not provided effective protection mechanisms preventing one user from effecting another user&#39;s data and programs without permission. Such protection mechanisms have not allowed unique, positive identification of users requesting access to information, or of information, nor have such mechanisms been sufficiently flexible in operation. In addition, access rights have pertained to the users rather than to the information, so that control of access rights has been difficult. Finally, prior art protection mechanisms have allowed the use of &#34;Trojan Horse arguments&#34;. That is, users not having access rights to certain information have been able to gain access to that information through another user or procedure having such access rights. 
     Yet another problem of the prior art is that of providing a simple and flexible interface user interface to a data processing system. The character of user&#39;s interface to a data processing system is determined, in part, by the means by which a user refers to and identifies operands and procedures of the user&#39;s programs and by the instruction structure of the system. Operands and procedures are customarily referred to and identified by some form of logical address having points of reference, and validity, only within a user&#39;s program. These addresses must be translated into logical and physical addresses within a data processing system each time a program is executed, and must then be frequently retranslated or generated during execution of a program. In addition, a user must provide specific instructions as to data format and handling. As such reference to operands or procedures typically comprise a major portion of the instruction stream of the user&#39;s program and requires numerous machine translations and operations to implement. A user&#39;s interface to a conventional system is thereby complicated, and the speed of execution of programs reduced, because of the complexity of the program references to operands and procedures. 
     A data processing system&#39;s instruction structure includes both the instructions for controlling system operations and the means by which these instructions are executed. Conventional data processing systems are designed to efficiently execute instructions in one or two user languages, for example, FORTRAN and COBOL. Programs written in any other language are not efficiently executable. In addition, a user is often faced with difficult programming problems when using any high level language other than the particular one or two languages that a particular conventional system is designed to utilize. 
     Yet another problem in conventional data processing systems is that of protecting the system&#39;s internal mechanisms, for example, stack mechanisms and internal control mechanisms, from accidental or malicious interference by a user. 
     Finally, the internal structure and operation of prior art data processing systems have not been flexible, or adaptive, in structure and operation. That is, the internal structure structure and operation of prior systems have not allowed the systems to be easily modified or adapted to meet particular data processing requirements. Such modifications may include changes in internal memory capacity, such as the addition or deletion of special purpose subsystems, for example, floating point or array processors. In addition, such modifications have significantly effected the users interface with the system. Ideally, the actual physical structure and operation of the data processing system should not be apparent at the user interface. 
     The present invention provides data processing system improvements and features which solve the above-described problems and limitations. 
     SUMMARY OF THE INVENTION 
     The present invention relates generally to digital computer systems and more specifically to digital computer systems employing object-based addressing of data. The digital computer system of the present invention includes a memory system including mass storage devices and one or more processors connected to the memory system. 
     The memory system is organized into objects containing data items. Each object is identified by an object identifier. Locations of data items in the memory system are specified by means of the object identifier for the object containing the data item and an offset specifying the bit at which the data item begins in the object. 
     Access to the data items in the object is controlled. When the digital computer system processes data in an object, it does so for a subject representing an entity using the computer system. An access control list associated with each object defines sets of subjects and a set of memory operations which a subject in a given set of subjects may perform on data items in the object. A memory operation on a data item in an object succeeds only if there is an access cntrol list entry associated with the object which allows the subject for whom the processor is performing the memory operation to perform that operation on the data in the object. 
     The data items include instructions which are executable by the processor. In the instructions, operands are represented by names. Each name in a procedure corresponds to a name table entry. Data in the name table entry corresponding to a name specifies how the processor is to derive the logical address of the operand represented by the name. 
     The memory system responds to a memory operation specifier consisting of a memory command specifying a memory operation such as read data or write data, a logical address containing a representation of an object identifier, an offset, and a length in bits and to a value representing the subject for which the processor is currently executing a procedure. In response to each memory operation specifier, the memory system checks to determine whether the current subject can perform the operation specified in the memory command on data contained in the object specified by the logical address. If the current subject cannot, the memory system does not perform the operation. 
     The processor includes instruction decoding apparatus, logical address generating apparatus which generates logical addresses, and control apparatus for controlling the processor in response to signals from the other components and the memory system and providing memory commands to the memory system. The logical address generation apparatus generates a logical address for a data item represented by a name by performing a resolve operation on the name. In that operation, the logical address generator derives the logical address as specified in the name table entry corresponding to the name. The logical address generation hardware also generates the logical address of the next instruction to be executed. 
     Execution of an instruction by the processor proceeds as follows: The logical address generator generates the address of the next instruction, and the processor outputs a memory command containing that address to the memory system. The memory system then outputs the instruction to the processor. The instruction decoder decodes the operation code, and in response to the instruction decoder, the control apparatus causes the logical address generation apparatus to resolve the names in the instruction. The processor produces a memory operation specifier for data by outputting the logical address produced by the logical address generation apparatus together with a memory command produced by the control apparatus. 
     It is thus an object of the present invention to provide an improved data processing system. 
     It is another object of the present invention to provide a data processing system capable of use in large, interconnected data processing networks. 
     It is yet another object of the present invention to provide an improved addressing mechanism suitable for use in large, interconnected data processing networks. 
     It is a further object of the present invention to provide an improved information protection mechanism. 
     It is still another object of the present invention to provide a simplified and flexible user interface to a data processing system. 
     It is yet a further object of the present invention to provide an improved mechanism for referring to operands. 
     It is a still further object of the present invention to provide an instruction structure allowing efficient data processing system operation with a plurality of high level user languages. 
     It is a further object of the present invention to provide data processing internal mechanisms protected from user interference. 
     It is yet another object of the present invention to provide a data processing system having a flexible internal structure capable of multiple, concurrent operations. 
     Other objects, advantages and features of the present invention will be understood by those of of ordinary skill in the art, after referring to the following detailed description of the preferred embodiments and drawings wherein: 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a partial block diagram of a computer system incorporating the present invention. 
    
    
     This application incorporates by reference the entire application, Ser. No. 266,402, filed on May 22, 1981, of Baxter et al., now issued as U.S. Pat. No. 4,455,602, on June 19, 1984.