Inventors:
Lee Silverthorn - Paradise Valley AZ
Curtis Cornils - Phoenix AZ
Mark L. Kirchner - Phoenix AZ
Susan D. Stephens - Chandler AZ
Parker E. Crouse - Chandler AZ
Assignee:
Motorola, Inc. - Schaumburg IL
International Classification:
G06F 1500
G06F 1200
G06F 1312
Abstract:
A computer (20) includes a hardware memory access enforcer (50) to insure that various independent programs (52, 54) operating on the computer (20) follow isolated processing rules. Each program has its own memory domain (56), which may extend across instruction, data, and I/O memory spaces (40, 42, 44). A system controller program (52) is a trusted process. The system controller (52) may access memory in the domain (56) of any application (54), and program flow may exit system controller (52) to any application (54). However, applications (54) cannot access memory outside of their own domains (56), and program flow may not exit applications (54) to enter other applications (54). Program flow may exit applications (54) to system controller (52) only if directed to an entry address (60). A tracking circuit (74) verifies that a microprocessor (22) actually executes entry instructions (94) located at the entry address (60).