EJTAG Debugging In Loongson3A System

In2001, Institute Of Computing Technology Chinese Academy Of Sciencesestablished a research team named "Loongson" to develop China’s own CPU. The team isestablished to assure the security of the information systems used by the military,government, state-owned enterprises and research institutions. With the help of the open-source Linux system, Loongson computer will greatly reduce the risk of the nationalinformation network. Debugging plays a very important role in the development of thenew system, and a good debugger can greatly speed up the process of the research.Unfortunately, most available debuggers are designed for applications other than kernels.What’s more, the few kernel debuggers can not work well on the loogson3A processorplatform.This project examines how to use EJTAG to do source-level debugging of the Linuxkernel under the Loongson3Aprocessor platform.This article first introduces domestic and foreign kernel debugging Research,compares the advantages and disadvantages of EJTAG debug and other kernel debugmethods. Some basic concepts are introduced later to make preparation for the debugsystem. Subsequently, the article describes the structure of the EJTAG debug system. Next,the article describes the instruction-level debugging, explains how to implement a CPUinstruction from the parallel port operation, thus achieving the read-write memory andregisters purposes. Then the debugger works with libdwarf library to implement source-level debugging. You can print variable or set breakpoints with it.