构建 ARM Linux 4.7.3 嵌入式开发环境 —

上一篇我们已经成功将 ARM Linux 4.7.3 的内核利用 U-BOOT 引导了起来。但是细心的你会发现，引导到后面，系统无法启动，出现内核恐慌（Kernel Panic）。原因是找不到文件系统。为了让内核成功启动，我们还需要构建一个根文件系统。为了后期开发的方便，我们采用 NFS 网络文件系统。

利用 BusyBox 构建 mini 根文件系统

什么是 BusyBox ？

BusyBox 是一个遵循GPL协议、以自由软件形式发行的应用程序。Busybox在单一的可执行文件中提供了精简的Unix工具集，可运行于多款POSIX环境的操作系统，例如Linux（包括Android、Hurd、FreeBSD等等。由于BusyBox可执行文件尺寸小、并通常使用 Linux内核，这使得它非常适合使用于嵌入式系统。此外，由于BusyBox功能强大，因此有些人将 BusyBox 称为“嵌入式Linux的瑞士军刀”。

下载最新 BusyBox 源码

$ wget -c http://busybox.net/downloads/busybox-1.25.0.tar.bz2

$ tar xvf busybox-1.25..tar.bz2

$ cd busybox-1.25.

配置编译 BusyBox

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- defconfig

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- menuconfig

BusyBox Setting >> Build Options 勾选编译成静态文件。

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- install

$ cd _install

$ mkdir proc sys dev etc etc/init.d

$ touch etc/init.d/rcS

$ cat << EOF > etc/init.d/rcS

#!bin/sh

mount -t proc none /proc

mount -t sysfs none /sys

/sbin/mdev -s

EOF

$ chmod +x etc/init.d/rcS

$ sudo mkdir /rootfs

$ sudo pax -r -w -p e . /rootfs

$ sudo chmod  /rootfs -R

$ sudo chown -R nobody:nobody /rootfs

到这里，根文件系统的内容已经准备好了，接下来配置 NFS 。

NFS 服务配置

$ sudo apt install nfs-kernel-server

$ sudo touch /etc/exports

$ sudo cat << EOF > /etc/exports

/rootfs    *(rw,sync,no_root_squash,no_subtree_check)

EOF

$ sudo service start nfs-kernel-server.service

OK, 到这里 NFS 服务配置完毕。

最后的准备

确保 Kernel 配置了 NFS 支持模块。

File systems  --->

    [*] Network File Systems  --->

        <*>   NFS client support

        <*>     NFS client support for NFS version 3

        [*]       NFS client support for the NFSv3 ACL protocol extension

        [*]   Root file system on NFS

修改 U-BOOT 传递给内核的引导参数

想要开机就生效，请参看本系列文章（一）,在编译 U-BOOT 时配置。

setenv bootargs 'root=/dev/nfs rw nfsroot=192.168.0.3:/rootfs init=/linuxrc console=ttyAMA0 ip=192.168.0.5'

启动系统

$ sudo qemu-system-arm -M vexpress-a9 -m 128M -nographic -net nic -net tap,ifname=tap0 -kernel u-boot



U-Boot 2016.07 (Sep 16 2016 - 11:18:06 +0800)

DRAM:  128 MiB

WARNING: Caches not enabled

Flash: 128 MiB

MMC:   MMC: 0

*** Warning - bad CRC, using default environment

In:    serial

Out:   serial

Err:   serial

Net:   smc911x-0

Hit any key to stop autoboot:  0

=> setenv bootargs 'root=/dev/nfs rw nfsroot=192.168.0.3:/home/rain/rootfs init=/linuxrc console=ttyAMA0 ip=192.168.0.5'

=> tftp 0x62000000 kernel

smc911x: MAC 52:54:00:12:34:56

smc911x: detected LAN9118 controller

smc911x: phy initialized

smc911x: MAC 52:54:00:12:34:56

Using smc911x-0 device

TFTP from server 192.168.0.3; our IP address is 192.168.0.5

Filename 'kernel'.

Load address: 0x62000000

Loading: #################################################################

     #################################################################

     #################################################################

     #################################################################

     #################################################################

     #################################################################

     #################################################################

     #################################################################

     #################################################################

     #################################################################

     ################################################

     1.6 MiB/s

done

Bytes transferred = 3571036 (367d5c hex)

smc911x: MAC 52:54:00:12:34:56

=> bootz 0x62000000

Kernel image @ 0x62000000 [ 0x000000 - 0x3643e8 ]

Starting kernel ...

Uncompressing Linux... done, booting the kernel.

Booting Linux on physical CPU 0x0

Linux version 4.7.3 (rain@rain-pc) (gcc version 5.4.0 20160609 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.1) ) #7 SMP Fri Sep 16 11:11:23 CST 2016

CPU: ARMv7 Processor [410fc090] revision 0 (ARMv7), cr=10c5387d

CPU: PIPT / VIPT nonaliasing data cache, VIPT nonaliasing instruction cache

Machine model: V2P-CA9

Memory policy: Data cache writeback

CPU: All CPU(s) started in SVC mode.

percpu: Embedded 13 pages/cpu @87eb8000 s23116 r8192 d21940 u53248

Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 32512

Kernel command line: root=/dev/nfs rw nfsroot=192.168.0.3:/home/rain/rootfs init=/linuxrc console=ttyAMA0 ip=192.168.0.5

log_buf_len individual max cpu contribution: 4096 bytes

log_buf_len total cpu_extra contributions: 12288 bytes

log_buf_len min size: 16384 bytes

log_buf_len: 32768 bytes

early log buf free: 14944(91%)

PID hash table entries: 512 (order: -1, 2048 bytes)

Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)

Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)

Memory: 121092K/131072K available (5261K kernel code, 161K rwdata, 1424K rodata, 1024K init, 155K bss, 9980K reserved, 0K cma-reserved)

Virtual kernel memory layout:

    vector  : 0xffff0000 - 0xffff1000   (   4 kB)

    fixmap  : 0xffc00000 - 0xfff00000   (3072 kB)

    vmalloc : 0x88800000 - 0xff800000   (1904 MB)

    lowmem  : 0x80000000 - 0x88000000   ( 128 MB)

    modules : 0x7f000000 - 0x80000000   (  16 MB)

      .text : 0x80008000 - 0x807875c0   (7678 kB)

      .init : 0x80800000 - 0x80900000   (1024 kB)

      .data : 0x80900000 - 0x809284a0   ( 162 kB)

       .bss : 0x8092a000 - 0x80950cc4   ( 156 kB)

SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1

Hierarchical RCU implementation.

    Build-time adjustment of leaf fanout to 32.

    RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=4.

RCU: Adjusting geometry for rcu_fanout_leaf=32, nr_cpu_ids=4

NR_IRQS:16 nr_irqs:16 16

GIC CPU mask not found - kernel will fail to boot.

GIC CPU mask not found - kernel will fail to boot.

L2C: platform modifies aux control register: 0x02020000 -> 0x02420000

L2C: DT/platform modifies aux control register: 0x02020000 -> 0x02420000

L2C-310 enabling early BRESP for Cortex-A9

L2C-310 full line of zeros enabled for Cortex-A9

L2C-310 dynamic clock gating disabled, standby mode disabled

L2C-310 cache controller enabled, 8 ways, 128 kB

L2C-310: CACHE_ID 0x410000c8, AUX_CTRL 0x46420001

smp_twd: clock not found -2

sched_clock: 32 bits at 24MHz, resolution 41ns, wraps every 89478484971ns

clocksource: arm,sp804: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275 ns

Console: colour dummy device 80x30

Calibrating local timer... 92.79MHz.

Calibrating delay loop... 516.09 BogoMIPS (lpj=2580480)

pid_max: default: 32768 minimum: 301

Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)

Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)

CPU: Testing write buffer coherency: ok

CPU0: thread -1, cpu 0, socket 0, mpidr 80000000

Setting up static identity map for 0x60100000 - 0x60100058

Brought up 1 CPUs

SMP: Total of 1 processors activated (516.09 BogoMIPS).

CPU: All CPU(s) started in SVC mode.

devtmpfs: initialized

VFP support v0.3: implementor 41 architecture 3 part 30 variant 9 rev 0

clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns

NET: Registered protocol family 16

DMA: preallocated 256 KiB pool for atomic coherent allocations

cpuidle: using governor ladder

of_amba_device_create(): amba_device_add() failed (-19) for /memory-controller@100e0000

of_amba_device_create(): amba_device_add() failed (-19) for /memory-controller@100e1000

of_amba_device_create(): amba_device_add() failed (-19) for /watchdog@100e5000

of_amba_device_create(): amba_device_add() failed (-19) for /smb@04000000/motherboard/iofpga@7,00000000/sysctl@01000

of_amba_device_create(): amba_device_add() failed (-19) for /smb@04000000/motherboard/iofpga@7,00000000/wdt@0f000

hw-breakpoint: debug architecture 0x4 unsupported.

Serial: AMBA PL011 UART driver

10009000.uart: ttyAMA0 at MMIO 0x10009000 (irq = 35, base_baud = 0) is a PL011 rev1

console [ttyAMA0] enabled

1000a000.uart: ttyAMA1 at MMIO 0x1000a000 (irq = 36, base_baud = 0) is a PL011 rev1

1000b000.uart: ttyAMA2 at MMIO 0x1000b000 (irq = 37, base_baud = 0) is a PL011 rev1

1000c000.uart: ttyAMA3 at MMIO 0x1000c000 (irq = 38, base_baud = 0) is a PL011 rev1

SCSI subsystem initialized

usbcore: registered new interface driver usbfs

usbcore: registered new interface driver hub

usbcore: registered new device driver usb

Advanced Linux Sound Architecture Driver Initialized.

clocksource: Switched to clocksource arm,sp804

NET: Registered protocol family 2

TCP established hash table entries: 1024 (order: 0, 4096 bytes)

TCP bind hash table entries: 1024 (order: 1, 8192 bytes)

TCP: Hash tables configured (established 1024 bind 1024)

UDP hash table entries: 256 (order: 1, 8192 bytes)

UDP-Lite hash table entries: 256 (order: 1, 8192 bytes)

NET: Registered protocol family 1

RPC: Registered named UNIX socket transport module.

RPC: Registered udp transport module.

RPC: Registered tcp transport module.

RPC: Registered tcp NFSv4.1 backchannel transport module.

hw perfevents: enabled with armv7_cortex_a9 PMU driver, 1 counters available

futex hash table entries: 1024 (order: 4, 65536 bytes)

workingset: timestamp_bits=29 max_order=15 bucket_order=0

squashfs: version 4.0 (2009/01/31) Phillip Lougher

jffs2: version 2.2. (NAND) © 2001-2006 Red Hat, Inc.

9p: Installing v9fs 9p2000 file system support

io scheduler noop registered (default)

clcd-pl11x 10020000.clcd: PL111 rev2 at 0x10020000

clcd-pl11x 10020000.clcd: /clcd@10020000 hardware, 1024x768@59 display

Console: switching to colour frame buffer device 128x48

clcd-pl11x 1001f000.clcd: PL111 rev2 at 0x1001f000

clcd-pl11x 1001f000.clcd: /smb@04000000/motherboard/iofpga@7,00000000/clcd@1f000 hardware, 640x480@59 display

40000000.flash: Found 2 x16 devices at 0x0 in 32-bit bank. Manufacturer ID 0x000000 Chip ID 0x000000

Intel/Sharp Extended Query Table at 0x0031

Using buffer write method

40000000.flash: Found 2 x16 devices at 0x0 in 32-bit bank. Manufacturer ID 0x000000 Chip ID 0x000000

Intel/Sharp Extended Query Table at 0x0031

Using buffer write method

Concatenating MTD devices:

(0): "40000000.flash"

(1): "40000000.flash"

into device "40000000.flash"

libphy: smsc911x-mdio: probed

Generic PHY 4e000000.etherne:01: attached PHY driver [Generic PHY] (mii_bus:phy_addr=4e000000.etherne:01, irq=-1)

smsc911x 4e000000.ethernet eth0: MAC Address: 52:54:00:12:34:56

isp1760 4f000000.usb: bus width: 32, oc: digital

isp1760 4f000000.usb: NXP ISP1760 USB Host Controller

isp1760 4f000000.usb: new USB bus registered, assigned bus number 1

isp1760 4f000000.usb: Scratch test failed.

isp1760 4f000000.usb: can't setup: -19

isp1760 4f000000.usb: USB bus 1 deregistered

usbcore: registered new interface driver usb-storage

mousedev: PS/2 mouse device common for all mice

rtc-pl031 10017000.rtc: rtc core: registered pl031 as rtc0

mmci-pl18x 10005000.mmci: Got CD GPIO

mmci-pl18x 10005000.mmci: Got WP GPIO

mmci-pl18x 10005000.mmci: mmc0: PL181 manf 41 rev0 at 0x10005000 irq 31,32 (pio)

ledtrig-cpu: registered to indicate activity on CPUs

usbcore: registered new interface driver usbhid

usbhid: USB HID core driver

input: AT Raw Set 2 keyboard as /devices/platform/smb@04000000/smb@04000000:motherboard/smb@04000000:motherboard:iofpga@7,00000000/10006000.kmi/serio0/input/input0

aaci-pl041 10004000.aaci: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 30

aaci-pl041 10004000.aaci: FIFO 512 entries

oprofile: using arm/armv7-ca9

NET: Registered protocol family 17

9pnet: Installing 9P2000 support

Registering SWP/SWPB emulation handler

rtc-pl031 10017000.rtc: setting system clock to 2016-09-19 05:56:32 UTC (1474264592)

smsc911x 4e000000.ethernet eth0: SMSC911x/921x identified at 0x892a0000, IRQ: 28

input: ImExPS/2 BYD TouchPad as /devices/platform/smb@04000000/smb@04000000:motherboard/smb@04000000:motherboard:iofpga@7,00000000/10007000.kmi/serio1/input/input2

IP-Config: Guessing netmask 255.255.255.0

IP-Config: Complete:

     device=eth0, hwaddr=52:54:00:12:34:56, ipaddr=192.168.0.5, mask=255.255.255.0, gw=255.255.255.255

     host=192.168.0.5, domain=, nis-domain=(none)

     bootserver=255.255.255.255, rootserver=192.168.0.3, rootpath=

ALSA device list:

  #0: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 30

VFS: Mounted root (nfs filesystem) on device 0:12.

Freeing unused kernel memory: 1024K (80800000 - 80900000)

nfs: server 192.168.0.3 not responding, still trying

nfs: server 192.168.0.3 OK

Please press Enter to activate this console.

/ # ls

bin      dev      etc      linuxrc  proc     sbin     sys      usr

/ # ip a

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1

    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

    inet 127.0.0.1/8 scope host lo

       valid_lft forever preferred_lft forever

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000

    link/ether 52:54:00:12:34:56 brd ff:ff:ff:ff:ff:ff

    inet 192.168.0.5/24 brd 192.168.0.255 scope global eth0

       valid_lft forever preferred_lft forever

/ # uname -a

Linux 192.168.0.5 4.7.3 #7 SMP Fri Sep 16 11:11:23 CST 2016 armv7l GNU/Linux

/ #

参考文章

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