Comment linux kernel code

learn linux kernel with qemu simulator 编译kernel，制作rootfs，配置qemu参数，主要用来使用gdb学习、分析调试linux kernel、uboot

how to use

sudo apt-get install gdb-arm-none-eabi gcc-arm-linux-gnueabi
./scripts/download.sh
make all

qemu options you can speicify:

• -S hold in the first instruction
• -s gdb server with port 1234

how to debug with gdb

waiting for composing

about making rootfs

• how many ways to identify a rootfs ?

how to use tap netdevice in qemu

first, sudo apt install uml-utilities bridge-utils

install tap netdevice

sudo ./setup-net.sh for example: sudo ./setup-net.sh eth0 $(whoami)

remove tap netdevice

sudo ./rm-net.sh

Tips

• only support assign ip via DHCP
• The IP assignment maybe fail, commonly because DHCP, then you will lose the connection to the host when you login via ssh/telnet

Questions

• 什么情况下会使用到skb链表？处理分片时？
• skb->truesize 有啥用
• _____alloc_skb 中，skbuff_head_cache skbuff_fclone_cache 的区别，为fast clone专门设计了一个memory ?
• skb 是什么的缩写 ? socket buffer
• what does skb->data_len represent ?