嵌入式微处理器保护方式下高特权级系统调用的研究

Research on High Privilege System Call in Protected Mode of Embedded Microprocessor

设计拥有我国自主版权的微处理器有着重大意义 .高特权级系统调用算法及高特权级系统调用测试单元PCU是拥有保护机制微处理器的重要组成部分 ,文中探讨了保护方式下高特权级系统调用的数据结构、定义 ,给出了高特权级系统调用算法 ,提出了高特权级系统调用测试单元 PCU的细胞群结构 ,并指出细胞是高特权级系统调用测试单元 PCU的基本测试单位 .细胞群结构概念的提出解决了微处理器保护测试单元结构设计的难题 ,使设计拥有自主版权的支持保护方式的微处理器成为可能 .细胞群结构已用于航空嵌入式拥有保护机制微处理器 NCS的设计 ,经 EDA工具 MENTOR GRAPHICS仿真与综合 。

High privilege system call is the only way for low privilege procedure to obtain system service in protected mode. In order to prevent low privilege procedure from interfering with high privilege procedure, a call gate data structure is used to protect system call. Only if call gate checkup passes, control could transfer from low privilege level to high privilege level. After analyzing definition and data structures of system calls, an algorithm is given to implement them. A basic test unit called cell is extracted from the algorithm, it produces Boolean test value to control branch of the microprogram for system call. Cells are enumerated and extracted from system call algorithm to form a kind of cell group to establish Privileged system Call test Unit (PCU). Cell group solves a difficult problem in protected test unit design in protected microprocessor, and it has been used in the design of aviation embedded 16 bit microprocessor NCS. VHDL description at RTL level for PCU and the algorithm microprogram have been successfully synthesized and simulated with MENTOR GRAPHICS of EDA tools and its simulation proves the validity of PCU.