$r16->$r17

Characters can be printed on the screen. Support partial stack backtracking

This part does not involve hardware issues, so it can be advanced quickly, but the reader needs to fully understand the synchronization issues of the operating system

Since the process mechanism of the loongarch platform is different from that of riscv, the implementation of threads also needs to be modified. The main focus is on the kernel stack and trap context.

Note that the matrix bug is triggered here, which needs to be fixed later

Need to pay attention to compiler related errors, including two panic expansion functions

Close the external interrupt correlation, test the accuracy of the file system

use isomorphic_drivers and pci-rs in rcore-os repository

Complete pci device scans, probe stat devices, and modify other libraries to support the loonarch platform. Write a simple keyboard device driver. Add external interrupt support

Preliminarily completed the abstraction of the process in Chapter 5, and
made some changes according to the platform characteristics of
loongarch, but there are still some bugs in the current system that need
to be resolved, and these bugs come from memory management.

Re-modified the address mapping space. This enables the kernel to manage the virtual memory space as if it were directly managing physical memory, and the kernel does not need to perform address translation.

Because the hardware characteristics of loongarch are quite different from those of riscv, the changes in this chapter are relatively large, and because the behavior of privileged instructions is difficult to debug, although the basic work has been completed, it still cannot work normally.