参考文章：
MIT OSLab
MIT Index of /2020/labs
xv6-riscv-book 中文版
https://github.com/FrankZn/xv6-riscv-book-Chinese/blob/main/Chapter-3.md
https://github.com/ranxian/xv6-chinese
https://th0ar.gitbooks.io/xv6-chinese/content/content/chapter0.html
原文
https://pdos.csail.mit.edu/6.828/2012/xv6/book-rev7.pdf
RISC-V手册
http://riscvbook.com/chinese/RISC-V-Reader-Chinese-v2p1.pdf
https://blog.csdn.net/weixin_47037146/article/details/128859088
https://mit-public-courses-cn-translatio.gitbook.io/mit6-s081/lec11-thread-switching-robert/11.1-thread
xv6-riscv源码
https://github.com/mit-pdos/xv6-riscv
https://github.com/ejunjsh/myxv6/tree/main
https://blog.xen.lol/2021/02/04/mit-6-S081-lab/
https://blog.csdn.net/u013577996/article/details/109582932
https://hitsz-cslab.gitee.io/os-labs/lab1/part2/#11
http://xv6.dgs.zone/
https://csdiy.wiki/%E6%93%8D%E4%BD%9C%E7%B3%BB%E7%BB%9F/NJUOS/
南大操作系统
https://jyywiki.cn/
https://jyywiki.cn/OS/2022/slides/18.slides.html#/
https://www.zhihu.com/question/598621331
RISC V 指令 jalr：jump and link register