裁剪Linux内核，用qemu进行调试

1. 内核编译

1. 进入到下载好的Linux内核文件中，将配置文件中的选项清空

   make allnoconfig
   

2. make menuconfig 进入配置文件菜单选项，将以下选择勾选

   64-bit kernel ---> yes
   General setup ---> Initial RAM filesystem and RAM disk (initramfs/initrd) support ---> yes
   General setup ---> Configure standard kernel features ---> Enable support for printk ---> yes
   Executable file formats / Emulations ---> Kernel support for ELF binaries ---> yes
   Executable file formats / Emulations ---> Kernel support for scripts starting with #! ---> yes
   Device Drivers ---> Generic Driver Options ---> Maintain a devtmpfs filesystem to mount at /dev ---> yes
   Device Drivers ---> Generic Driver Options ---> Automount devtmpfs at /dev, after the kernel mounted the rootfs ---> yes
   Device Drivers ---> Character devices ---> Enable TTY ---> yes
   Device Drivers ---> Character devices ---> Serial drivers ---> 8250/16550 and compatible serial support ---> yes
   Device Drivers ---> Character devices ---> Serial drivers ---> Console on 8250/16550 and compatible serial port ---> yes
   File systems ---> Pseudo filesystems ---> /proc file system support ---> yes
   File systems ---> Pseudo filesystems ---> sysfs file system support ---> yes
   

1. 编译内核,差不多只有1M

   sudo make -j8
   

   

2. 使用busybox构建根文件系统

1. 进入busybox文件夹，使用默认的配置文件

   make defconfig
   

2. make menuconfig 编辑配置文件，一定开启静态编译

   Busybox Settings ---> Build Options ---> Build BusyBox as a static binary (no shared libs) ---> yes
   

3. 编译busybox

   time make -j 8
   

4. 安装busybox, install之后出现_install 文件夹

   make install
   

5. cd _install 创建一些文件夹以及文件

   • mkdir -p proc sys dev etc etc/init.d lib tmp
     

   • ln -sf linuxrc init
     

   • cat > etc/init.d/rcS <<EOF
     #!/bin/sh
     mount -t proc none /proc
     mount -t sysfs none /sys
     /sbin/mdev -s
     ifconfig lo up
     EOF
     

   • chmod +x etc/init.d/rcS
     

   • cat > etc/inittab <<EOF
     # /etc/inittab
     ::sysinit:/etc/init.d/rcS
     ::askfirst:-/bin/sh
     ::ctrlaltdel:/sbin/reboot
     ::shutdown:/bin/umount -a -r
     EOF
     

6. 使用cpio生成根文件系统

   find . -print0 | cpio --null -ov --format=newc   | gzip -9 > ../initramfs.cpio.gz
   

7. busybox文件夹中，解压刚才生成的initramfs.cpio.gz为initramfs.cpio

3. 使用qemu启动编译好的内核

• qemu-system-x86_64 -kernel ~/Desktop/linux-4.14/arch/x86/boot/bzImage -initrd initramfs.cpio