A hardware architecture for implementing protection rings

Michael D. Schroeder, Jerome H. Saltzer
1971 Proceedings of the third symposium on Operating systems principles - SOSP '71  
Protection of computations and information is an important aspect of a computer utility. In a system which uses segmentation as a memory addressing scheme, protection can be achieved in part by associating concentric rings of decreasing access privilege with a computation. This paper describes hardware processor mechanisms for implementing these rings of protection. The mechanisms allow cross-ring calls and subsequent returns to occur without trapping to the supervisor. Automatic hardware
more » ... tion of references across ring boundaries is also performed. Thus, a call by a user procedure to a protected subsystem (including the the supervisor) is identical to a call to a companion user procedure. The mechanisms of passing and referencing arguments are the same in both cases as well.
doi:10.1145/800212.806498 dblp:conf/sosp/SchroederS71 fatcat:f3fxqui7bvbvhm7u7ve2rdcgaq