Abstract

moters of these systems imply that their reliability and integrity derive solely from the use of a core set of protected hardware mechanisms, such as address spaces and protected supervisor mode [Custer 93, Cheriton & Duda 94]. While typical microprocessors provide cheap and effective hardware mechanisms to protect the "load word/store word" interface, operating systems are forced to abstract and virtualize this interface to export a far richer set of resources such as files, sockets, threads, and consoles. The access semantics for these resources are almost always protected by software checks and not hardware. For example, protection issues such as "should I allow this process to terminate that process?", "is there enough memory to spawn a new task", "has that thread had more than its share of CPU time", "can I write to that file" or "can this process really halt the machine?" are not typically resolved automatically in hardware. Processor architectures simply do not provide enough fi

Citations