privileged instruction การใช้

• Processor Privilege controls the ability to execute privileged instructions and access protected registers and other state.
• Non-privileged instructions must instead be executed natively ( i . e ., efficiently ).
• The instructions available in this state were the non-privileged instructions of the IBM System 360.
• The separated privileged instruction-set permits research in operating system-support, without redesigning compilers.
• Unlike virtual memory, a system virtual machine entitled the user to write privileged instructions in their code.
• In supervisor mode, the stack registers point to the system stack and all privileged instructions are available.
• A new " monitor mode " limits access to input / output and certain privileged instructions.
• In user mode, the stack registers point to the normal stack and all privileged instructions will generate a fault.
• The use of rings allows for system software to restrict tasks from accessing data, call gates or executing privileged instructions.
• VMM may be constructed if the set of sensitive instructions for that computer is a subset of the set of privileged instructions.
• Resources ( segments, pages, ports, etc . ) and the privileged instructions are tagged with a demanded privilege level.
• Due to the proliferation of Intel microprocessors, the existence of this open privilege instruction was considered a serious issue at the time.
• The system architecture and instruction-set were largely compatible with the non-privileged instruction-set of the IBM System / 360.
• This mechanism was also used to implement privileged instruction, dynamic profiling ( for performance monitoring ) and multiple CPU modes ( e . g.
• PP = 1 restricts most privileged instructions but does allow reading of the day clocks and reading the contents of some of the privileged registers.
• VMM may be constructed for any third generation machine in which the set of user sensitive instructions are a subset of the set of privileged instructions:
• Drivers cannot execute privileged instructions, change the page tables, perform arbitrary input / output ( I / O ), or write to absolute memory.
• Zheng Yin s close relationship to Ge s family, through Ge Xuan, might have naturally led to Ge Hong s privileged instruction in important esoteric texts.
• The assembly language ( known as Usercode ) non-privileged instruction set was identical to IBM System 360 Assembly Language; in privileged mode there were a few extras.
• The privileged instruction set specification explicitly defines " hardware threads, " or " harts . " Multiple hardware threads are a common practice in larger, more powerful computers.