Browse Prior Art Database

Program Protection Method

IP.com Disclosure Number: IPCOM000050163D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Griscom, RE: AUTHOR [+2]

Abstract

The method described herein is useful for determining that the execution of a computer system follows rules intended to assure its coorect operation. This method involves the use of bit masks to define capabilities of code in execution, so as to allow the detection of violations of these capabilities.

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Program Protection Method

The method described herein is useful for determining that the execution of a computer system follows rules intended to assure its coorect operation. This method involves the use of bit masks to define capabilities of code in execution, so as to allow the detection of violations of these capabilities.

In this method, the code is divided into main storage accessing regions, with each module assigned to one of the regions. Each region is represented by a bit mask which has only one bit on. A second bit mask is established for each such region. This bit mask indicates which regions may not store data into the associated region. Additional bit masks are established, one for each class of instructions to be treated as privileged. These bit masks indicate which regions are not allowed to issue the associated class of instructions. During the operation of the computer system, these bit masks are checked to detect rule violations, either bad store operations or unauthorized use of privileged instructions. This is done by "ANDing" the appropriate capability mask with the region mask corresponding to the location of the instruction. A non-zero result indicates a violation.

This method is useful for simulators of computer systems in which the processors do not have adequate storage or privileged instruction protection capabilities built into their hardware, such as microprocessors. This method is also useful in the development systems for such comp...