Linux最小内核移植

╰半夏微凉° 2022-05-30 10:53 245阅读 0赞

**Linux内核编译**  
本篇博客来自凌云实验室开发板介绍及其烧录学习笔记

# 1.内核介绍 #

一种开源电脑操作系统内核。它是一个用C语言写成，符合POSIX标准的类Unix操作系统。也就是，最上面是用户（或应用程序）空间，程序执行的地方。\*\*函数库(glibc或uclibc)\*\*提供了连接内核的系统调用接口，还提供了在用户空间应用程序和内核之间进行转换的机制。区别于51，stm32单片机等，每个用户空间的进程都使用自己的虚拟地址空间，而内核则占用单独的地址空间。  
![Linux内核][Linux]

# 2.内核下载 #

现在内核更新的比较快，我们为s3c2440选择3.0版本。附上内核下载[链接][Link 1]。  
![内核][70]

# 3.文件准备 #

博主使用的是三星的ARM9 S3C2440，该cpu是以armv4t指令集的ARM920t，跑ARM Linux的开发板时，以SMDK2440为模板支持相应的硬件。建立整体框架。

[klaus@localhost ~]$ mkdir fl2440
    [klaus@localhost ~]$ cd fl2440/
    [klaus@localhost fl2440]$ mkdir -p {crosstool,bootloader,linux/{kernel,rootfs},driver,3rdparty,program,images}
    [klaus@localhost fl2440]$ tree
    .
    ├── 3rdparty
    ├── bootloader
    ├── crosstool
    ├── driver
    ├── images
    ├── linux
    │   ├── kernel
    │   └── rootfs
    └── program
    
    9 directories, 0 files
    [klaus@localhost fl2440]

# 4.内核修改编译 #

下载源代码后，修改成自己单片机相应的类型  
一般为开发板型号  
![3.1][]  
其他型号都不需要选择，只选择**s3c2440 and s3c2442 Machines**  
![111][3.1]  
不同需要，比如更改**串口驱动设备**，自己的**交叉编译器**等等。  
编译前可以查看一下C文件和汇编文件的多少，当然我这个是内核生成之后的文件个数。

[klaus@localhost linux-3.0]$ find -name *.c | wc -l
    16563
    [klaus@localhost linux-3.0]$ find -name *.S | wc -l
    1226
    [klaus@localhost linux-3.0]$

# 5. 有趣的三角 #

拟写一个shell脚本，博主会在另一篇文章详细讲解，文章链接在这里。

#!/bin/bash
    make
    mkimage -A arm -O linux -T kernel -C none -a 30008000 -e 30008040 -n "Linux Kernel" -d arch/arm/boot/zImage linuxrom-s3c2440.bin
    chmod a+x linuxrom-s3c2440.bin

执行脚本后就可以查看生成结果了

[klaus@localhost linux-3.0]$ chmod a+x build.sh
    [klaus@localhost linux-3.0]$ ./build.sh
    
    ... ... ...
    Image Name:   Linux Kernel
    Created:      Thu Mar 15 11:58:01 2018
    Image Type:   ARM Linux Kernel Image (uncompressed)
    Data Size:    2314180 Bytes = 2259.94 kB = 2.21 MB
    Load Address: 30008000
    Entry Point:  30008040
    [klaus@localhost linux-3.0]$ ls
    arch      CREDITS        firmware  ipc      lib                   mm               net             scripts     tools    vmlinux.o
    block     crypto         fs        Kbuild   linuxrom-s3c2440.bin  modules.builtin  README          security    usr
    build.sh  Documentation  include   Kconfig  MAINTAINERS           modules.order    REPORTING-BUGS  sound       virt
    COPYING   drivers        init      kernel   Makefile              Module.symvers   samples         System.map  vmlinux
    [klaus@localhost linux-3.0]$

# 6.可能遇到的问题 #

\#\#\#\#\#1）格式错误

... ... ...
    [klaus@localhost linux-3.0]$ make s3c2410_defconfig
    make: *** /home/klaus/fl2440/linux/linux-3.0/arch/arm: Is a directory.  Stop.

解决办法，在改文件路径时，多空格少换号都不行，要严格注意

export KBUILD_BUILDHOST := $(SUBARCH)
    ARCH            ?=arm
    CROSS_COMPILE   ?=/opt/x-tools/arm920t/bin/arm-linux-

楼主我出现这个问题是因为我多打了一个空格，arm后面。  
\#\#\#\#2）缺少依赖

... ... ...
    IHEX2FW firmware/emi62/spdif.fw
    IHEX2FW firmware/emi62/midi.fw
    ./build.sh:line 3:mkimage:command not found
    chmod:cannot access `linuxrom-s3c2440.bin`:No such file or directory
    [klaus@localhost linux-3.0]$

可能是缺少uboot-tools之间这个依赖，可以直接下载这个安装包进行安装

[klaus@localhost ~]$ wget http://rpmfind.net/linux/epel/6/x86_64/Packages/u/uboot-tools-2011.03-1.el6.x86_64.rpm
    [klaus@localhost ~]$ sudo rpm -ivh uboot-tools-2011.03-1.el6.x86_64.rpm

# 7.烧录到开发板 #

内核生成后，我们可以尝试将这个.bin文件烧录到现有的开发板上去，看看现象会怎样  
这里在u-boot界面采用tftp下载到开发板

U-Boot 2010.09 (May 05 2017 - 19:48:28)
    
    DRAM:  64 MiB
    NAND:  256 MiB
    In:    serial
    Out:   serial
    Err:   serial
    Net:   dm9000
    Hit any key to stop autoboot:  0 
    [fl2440@lingyun]#
    [fl2440@lingyun]# run tb
    dm9000 i/o: 0x20000300, id: 0x90000a46 
    DM9000: running in 16 bit mode
    MAC: 00:11:22:33:44:55
    could not establish link
    Using dm9000 device
    TFTP from server 192.168.100.8; our IP address is 192.168.100.18
    Filename 'linuxrom-s3c2440.bin'.
    Load address: 0x30008000
    Loading: #################################################################
             #################################################################
             ##########################################################
    done
    Bytes transferred = 2752308 (29ff34 hex)
    ## Booting kernel from Legacy Image at 30008000 ...
       Image Name:   Linux Kernel
       Created:      2017-06-19  22:03:17 UTC
       Image Type:   ARM Linux Kernel Image (uncompressed)
       Data Size:    2752244 Bytes = 2.6 MiB
       Load Address: 30008000
       Entry Point:  30008040
       Verifying Checksum ... OK
       XIP Kernel Image ... OK
    OK
    
    Starting kernel ...
    
    Uncompressing Linux... done, booting the kernel.
    Linux version 3.0.0 (guowenxue@centos6.localdomain) (gcc version 4.5.4 (Buildroot 2012.08) ) #2 Tue Jun 20 06:03:14 CST 2017
    CPU: ARM920T [41129200] revision 0 (ARMv4T), cr=c0007177
    CPU: VIVT data cache, VIVT instruction cache
    Machine: SMDK2440
    Memory policy: ECC disabled, Data cache writeback
    CPU S3C2440A (id 0x32440001)
    S3C24XX Clocks, Copyright 2004 Simtec Electronics
    S3C244X: core 405.000 MHz, memory 101.250 MHz, peripheral 50.625 MHz
    
    ... ... ... 
    
    arp_tables: (C) 2002 David S. Miller
    TCP cubic registered
    NET: Registered protocol family 17
    lib80211: common routines for IEEE802.11 drivers
    Registering the dns_resolver key type
    s3c-rtc s3c2410-rtc: setting system clock to 2017-10-31 02:57:07 UTC (1509418627)
    Root-NFS: no NFS server address
    VFS: Unable to mount root fs via NFS, trying floppy.
    VFS: Cannot open root device "(null)" or unknown-block(2,0)
    Please append a correct "root=" boot option; here are the available partitions:
    1f00            1024 mtdblock0  (driver?)
    1f01           15360 mtdblock1  (driver?)
    1f02           40960 mtdblock2  (driver?)
    1f03           81920 mtdblock3  (driver?)
    1f04           81920 mtdblock4  (driver?)
    1f05           40960 mtdblock5  (driver?)
    Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
    Backtrace: 
    [<c003b2cc>] (dump_backtrace+0x0/0x110) from [<c040f60c>] (dump_stack+0x18/0x1c)
     r6:00008000 r5:c38ac000 r4:c056dd40 r3:c05446d4
    [<c040f5f4>] (dump_stack+0x0/0x1c) from [<c040f66c>] (panic+0x5c/0x17c)
    [<c040f610>] (panic+0x0/0x17c) from [<c0008de0>] (mount_block_root+0x1c8/0x208)
     r3:00000000 r2:20000013 r1:c3819f58 r0:c04c32ed
     r7:c04c3351
    [<c0008c18>] (mount_block_root+0x0/0x208) from [<c0008fc8>] (mount_root+0xac/0xd0)
    [<c0008f1c>] (mount_root+0x0/0xd0) from [<c000914c>] (prepare_namespace+0x160/0x1b4)
     r4:c056d680
    [<c0008fec>] (prepare_namespace+0x0/0x1b4) from [<c00089d4>] (kernel_init+0xe4/0x118)
     r5:c0025d3c r4:c056d620
    [<c00088f0>] (kernel_init+0x0/0x118) from [<c004d8ac>] (do_exit+0x0/0x624)
     r5:c00088f0 r4:00000000

系统会报出 \*\*Unable to mount root fs on unknown-block(2,0)\*\*这样的错误，这时候就是缺少根文件系统了，下一步，将根文件系统树烧进内核中绑定一起就以可以将系统跑起来，[这里文件系统的制作链接][Link 2]。

[Linux]: /images/20220530/7abfc1f920034d0aa36e393d3a5454d3.png
[Link 1]: https://www.kernel.org/pub/linux/kernel/
[70]: /images/20220530/e4fbaee6b9cb4630a8cb612691380571.png
[3.1]: 
[Link 2]: https://blog.csdn.net/klaus_x/article/details/79805166