kernel

Author: jiaxianhua

_posts/2020-12-30-linux-kernel.md

@@ -0,0 +1,91 @@
+---
+layout: post
+title: "LinuxLab 真板开发：内核构建"
+author: iosdevlog
+date: 2020-12-30 17:09:32 +0800
+description: ""
+cover-img: /assets/images/LinuxLab/IMX6ULL/kernel.png
+category: 
+tags: [LinuxLab, IMX6ULL, linux, kernel]
+---
+
+## 切换到ebf-imx6ull
+
+```bash
+make BOARD=arm/ebf-imx6ull
+git branch
+# * next
+```
+
+## 修改内核
+
+进入内核源码目录，做一些修改。
+
+```bash
+vi src/linux-stable/init/main.c
+```
+
+`kernel_init` 添加添加一条打印。
+
+ubuntu@linux-lab:/labs/linux-lab/src/linux-stable$ `git diff init/main.c`
+
+```diff
+diff --git a/init/main.c b/init/main.c
+index e083fac08aed..c8041fa17d6c 100644
+--- a/init/main.c
++++ b/init/main.c
+@@ -1078,6 +1078,8 @@ static int __ref kernel_init(void *unused)
+ 
+ 	rcu_end_inkernel_boot();
+ 
++	printk(KERN_DEBUG "Hello, IMX6ULL from Linux Lab.");
++
+ 	if (ramdisk_execute_command) {
+ 		ret = run_init_process(ramdisk_execute_command);
+ 		if (!ret)
+```
+
+编译安装
+
+```bash
+$ make kernel-build
+$ make modules-install
+```
+
+上传
+
+```bash
+make kernel-upload
+```
+
+启动新 Image
+
+```bash
+make boot
+```
+
+查看启动日志
+
+```bash
+debian@npi:~$ dmesg | grep from                                                
+[    0.000000] random: get_random_bytes called from start_kernel+0xa0/0x434 wi0
+[    0.000000] rcu:     RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=1.   
+[    1.543896] sii902x bound to mxs-lcdif from 21c8000.lcdif                   
+[    1.646126] Console IMX rounded baud rate from 114943 to 114900             
+[    7.438844] Hello, IMX6ULL from Linux Lab.                                  
+[    9.745109] fec 20b4000.ethernet eth2: renamed from eth0                    
+[   15.209116] systemd-journald[206]: Received request to flush runtime journa1
+```
+
+可以看到我们在 `init/main.c` 里添加的打印已经生效了。
+
+![kernel](/assets/images/LinuxLab/IMX6ULL/kernel.png)
+
+查看一下内核信息：
+
+```bash
+debian@npi:~$ uname -a                                                         
+Linux npi 4.19.35+ #2 SMP PREEMPT Wed Dec 30 17:33:39 CST 2020 armv7l GNU/Linux
+```
+
+是刚才编译的，说明我们修改的内核确实起作用了。