EBC Exercise 22 Cross-Compiling and Finding the Right Kernel - bitbake

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thumb‎ Embedded Linux Class by Mark A. Yoder


This class is about developing software for embedded Linux. So far we have been doing all of our development on the Beagle. This works well for small (and not so small) programs. However, we are now moving into kernel development and that's best done on a more powerful host computer. In EBC Exercise 08 Installing Development Tools you learned how to download and install the cross-compilers and the source for kernel and u-boot. Now we'll use those tools.

First we'll check everything by compiling the Hello World program, then we'll try the kernel and u-boot.

Stop Here, the rest hasn't been updated

Finding the Kernel and Installing It

After doing EBC Exercise 08 Installing Development Tools - bitbake you have a Beagle kernel on your host computer. Let's see if it works.

Once compiled the kernel is put in a file called uImage. You may have seen it in the FAT partition on your SD card. Let's find it on your host. One way to find it is

host$ cd ~/BeagleBoard/oe
host$ find . -name uImage
./build/tmp-angstrom_v2012_05-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-mainline-3.2.18-r121b/git/arch/arm/boot/uImage
./build/tmp-angstrom_v2012_05-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-mainline-3.2.18-r121b/sysroot-destdir/kernel/uImage
./build/tmp-angstrom_v2012_05-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-mainline-3.2.18-r121b/image/kernel/uImage
./build/tmp-angstrom_v2012_05-eglibc/sysroots/beagleboard/kernel/uImage

It looks like I've compile the 3.2.18 version of the kernel. What version is the beagle running?

beagle$ uname -a
Linux yoder-bone 3.2.25 #1 Fri Aug 10 10:33:12 CEST 2012 armv7l GNU/Linux

The bone is running 3.2.25. Here's how to get our sources to match those used to compile the 3.2.25 kernel.

beagle$ cat /etc/angstrom-build-info 
Configured Openembedded layers:
meta-angstrom     = angstrom-v2012.05-yocto1.2:a029f5f5d19f788e2ab17227f35350ff5b6ca125
meta-oe           
toolchain-layer   
meta-efl          
meta-gpe          
meta-gnome        
meta-xfce         
meta-initramfs    
meta-multimedia   = denzil:b4488f4c012a64604b28bd2b6e93de411c34466d
meta-opie         = master:efa3892b20a4ef80274e56e5633ebd62c16f9731
meta-java         = master:3386ea6c96096f107f43f282f654e5afa456109e
meta-browser      = master:c47f59df2e723495679c751cbdf6a8c6adec4b6a
meta-mono         = master:83f8233b0498aadb18bf7605c3ba6c71d9e13a3a
meta-kde          = master:5b0882d951cfd71886d423c190faaa7c7f932333
meta-ti           = angstrom-staging:5364d0795bb27c2deb5a4e2df7d2f01ffb394cca
meta-efikamx      = master:2c09a3a780b23448e8a6ca964256ff7f5ccba65d
meta-nslu2        = master:3d9fc951b05b4df476374b6fc3085ebac7f293ee
meta-htc          
meta-nokia        
meta-openmoko     
meta-palm         = master:2b106be01228f64298d6cb338f93088806594344
meta-handheld     = master:1f05a15aceb4c3a19fa070463b58125b5658b2a9
meta-raspberrypi  = denzil:34eef2ea4f5f24630dbb73b386861430167b8431
meta-intel        
meta-sugarbay     
meta-crownbay     
meta-emenlow      
meta-fishriver    
meta-fri2         
meta-jasperforest 
meta-n450         = master:f75f9b6f68473eb0efac802409608f8389be0030
meta              = denzil:b052427a6678b1b696f8c64cf0fdc55e6af86c48

This file shows the various repositories that were used to compile the kernel (and the root file system) for the given SD image (the bone A6A image in my case). Yes, the kernel comes from several git repositories. How many?

host$ cd ~/BeagleBoard/oe
host$ find . -name .git
./.git
./build/tmp-angstrom_v2012_05-eglibc/buildhistory/.git
./build/tmp-angstrom_v2012_05-eglibc/work/beagleboard-angstrom-linux-gnueabi/u-boot-2011.12-r8/git/.git
./build/tmp-angstrom_v2012_05-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-mainline-3.2.18-r121b/git/.git
./build/tmp-angstrom_v2012_05-eglibc/work/armv7a-angstrom-linux-gnueabi/mtd-utils-1.4.9-r1/git/.git
./sources/meta-xilinx/.git
./sources/meta-intel/.git
./sources/bitbake/.git
./sources/meta-efikamx/.git
./sources/meta-angstrom/.git
./sources/openembedded-core/.git
./sources/meta-handheld/.git
./sources/meta-kde/.git
./sources/meta-nslu2/.git
./sources/meta-openembedded/.git
./sources/meta-raspberrypi/.git
./sources/meta-mono/.git
./sources/meta-java/.git
./sources/meta-ti/.git
./sources/meta-ettus/.git
./sources/meta-openpandora/.git
./sources/meta-smartphone/.git
./sources/meta-opie/.git
./sources/meta-browser/.git

The first .git is the repository you cloned to do the initial bitbake. The next is the u-boot repository. The next one is the kernel's repository. We'll be using that repository so much you should set up a symbolic link to it so you can find it easily.

host$ ln -s ~/BeagleBoard/oe/build/tmp-angstrom_v2012_05-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-mainline-3.2.18-r121b/git/ ~/...

Notice several .gits are in the sources directory. Note they have many names in common with the contents of /etc/angstrom-build-info. These are the repositories where we need to checkout the commits that correspond to the tags above. Here's how, take the first repository with a tag and cd to it.

meta-angstrom

host$ cd sources/meta-angstrom/
/home/beagle/BeagleBoard/oe/sources/meta-angstrom
host$ git status
# On branch angstrom-v2012.05-yocto1.2
nothing to commit (working directory clean)
host$ git remote update
Fetching origin
remote: Counting objects: 132, done.
remote: Compressing objects: 100% (57/57), done.
remote: Total 105 (delta 53), reused 96 (delta 45)
Receiving objects: 100% (105/105), 16.95 KiB, done.
Resolving deltas: 100% (53/53), completed with 18 local objects.
From git://github.com/Angstrom-distribution/meta-angstrom
   140671a..784d76b  master     -> origin/master

Now checkout the corresponding tag

host$ git checkout a029f5f5d19f788e2ab17227f35350ff5b6ca125
Note: checking out 'a029f5f5d19f788e2ab17227f35350ff5b6ca125'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b new_branch_name

HEAD is now at a029f5f... base-files bbappend: move /var/run handling to systemd proper
host$ git status
# Not currently on any branch.
nothing to commit (working directory clean)

Don't worry that your HEAD is detached. That just means your not on a branch. However it is the commit that was used to create the kernel we want.

meta-opie

Now, repeat this for each of the hash tags in /etc/angstrom-build-info. I'll get you started, you finish it.

host$ cd ../meta-opie
/home/beagle/BeagleBoard/oe/sources/meta-opie
host$ git remote update
Fetching origin
host$ git checkout efa3892b20a4ef80274e56e5633ebd62c16f9731
HEAD is now at efa3892... opie-packagemanager: fix a couple more quoting issues

and so on...

Keep going until you get an error.

meta-ti

This repository pulls from more than one place so the checkout will fail. Here's what to do.

host$ cd ../meta-ti
host$ git remote update
host$ git checkout 5364d0795bb27c2deb5a4e2df7d2f01ffb394cca
fatal: reference is not a tree: 5364d0795bb27c2deb5a4e2df7d2f01ffb394cca

So what repository has the tag 5364d0795bb27c2deb5a4e2df7d2f01ffb394cca? Try google. With a bit of googling, I was able to find https://github.com/Angstrom-distribution/meta-ti/commit/5364d0795bb27c2deb5a4e2df7d2f01ffb394cca. Add this to the remote repositories.

host$ git remote add test https://github.com/Angstrom-distribution/meta-ti
host$ git remote update
host$ git checkout 5364d0795bb27c2deb5a4e2df7d2f01ffb394cca

Now continue on with the rest of the repositories.

Once all the repositories are all up to date

Now it's time to bitbake again and the 3.2.25 kernel should appear.

host$ cd ~/BeagleBoard/oe
host$ source ~/.oe/environment-angstromv2012.05
host$ time bitbake virtual/kernel

Finding the Kernel for the ETC 2012 image

We are looking for uImage, but we only want the 2.6.32 version. The last grep file the file in the boot directory. Several lines are printed, but the one I'm interested in is:

./build/tmp-angstrom_2010_x-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-omap-psp-2.6.32-r110b+gitr5fc29e7b2a76a64a739f857858ef0b98294aa155/git/arch/arm/boot/uImage

The first part of the path (in italics) is the path to the kernel. Check it out.

host$ cd build/tmp-angstrom_2010_x-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-omap-psp-2.6.32-r110b+gitr5fc29e7b2a76a64a739f857858ef0b98294aa155/git
host$ ls -F
arch/           drivers/   Kbuild       modules.order   samples/    usr/
block/          firmware/  kernel/      Module.symvers  scripts/    virt/
COPYING         fs/        lib/         net/            security/   vmlinux*
CREDITS         include/   MAINTAINERS  patches/        sound/      vmlinux.o
crypto/         init/      Makefile     README          System.map
Documentation/  ipc/       mm/          REPORTING-BUGS  tools/

We'll be learning what's in many of these over the next couple of weeks. Remember this location. Let's find uImage.

host$ cd arch/arm/boot; ls -shF
total 13M
4.0K bootp/       6.3M Image*      4.0K Makefile  3.0M zImage*
4.0K compressed/  4.0K install.sh  3.0M uImage
host$ ls -l uImage
-rw-r--r-- 1 beagle beagle 3144300 2011-12-08 01:02 uImage

It should have the date that you did the bitbake. Let's see if it runs on the Beagle

host$ scp uImage root@beagle:.
host$ ssh root@beagle
beagle$ cd /boot; ls -F
total 18M
4.0K MLO@
372K Module.symvers-2.6.32
1.4M System.map-2.6.32
 80K config-2.6.32
4.0K u-boot.bin@
   0 uImage@
3.1M uImage-2.6.32
8.9M vmlinux-2.6.32
beagle$ ls -l uImage
lrwxrwxrwx 1 www-data www-data 13 May 12  2011 uImage -> uImage-2.6.32

So the uImage that is there is a symbolic link to uImage-2.6.32. Let's save the working uImage in a difference file and copy our new uImage in.

beagle$ mv uImage-2.6.32 uImage-2.6.32.orig
beagle$ mv ~/uImage uImage-2.6.32

And then reboot.

beagle$ shutdown -r now

After a couple of minutes your should be back and running again. Check and see if you are really running the new kernel.

beagle$ uname -a
Linux beagleboard 2.6.32 #3 PREEMPT Thu Dec 8 01:02:13 EST 2011 armv7l GNU/Linux

It worked! That's the date I compiled mine on.

Failed Kernel

Here's what I get when trying to run the 3.2.18 kernel on the A6A bone image.

reading u-boot.img
reading u-boot.img


U-Boot 2011.09-00053-gb423c52 (Aug 10 2012 - 11:26:55)

I2C:   ready
DRAM:  256 MiB
WARNING: Caches not enabled
No daughter card present
NAND:  HW ECC Hamming Code selected
No NAND device found!!!
0 MiB
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
*** Warning - readenv() failed, using default environment

Net:   cpsw
Hit any key to stop autoboot:  0 
SD/MMC found on device 0
reading uEnv.txt

27 bytes read
Loaded environment from uEnv.txt
Importing environment from mmc ...
Loading file "/boot/uImage" from mmc device 0:2 xxa2
4385656 bytes read
## Booting kernel from Legacy Image at 80007fc0 ...
   Image Name:   Linux-3.2.18
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    4385592 Bytes = 4.2 MiB
   Load Address: 80008000
   Entry Point:  80008000
   Verifying Checksum ... OK
   XIP Kernel Image ... OK
OK

Starting kernel ...

Installing a New U-boot

While we're at it, let's install a new U-boot. Note: The new U-boot runs for me, but doesn't boot the kernel, yet.

host$ cd ~/BeagleBoard/oe/build/tmp-angstrom_2010_x-eglibc/work/beagleboard-angstrom-linux-gnueabi/
host$ ls -F
linux-3.0.9-r110a/
linux-omap-psp-2.6.32-r110b+gitr5fc29e7b2a76a64a739f857858ef0b98294aa155/
shadow-4.1.4.3-r5/
u-boot-2011.09-r4/

There's the U-boot directory.

host$ cd u-boot-2011.09-r4/git/; ls -F
api/        COPYING    fs/          mkconfig*     post/            tools/
arch/       CREDITS    include/     mmc_spl/      README           u-boot*
board/      disk/      lib/         nand_spl/     rules.mk         u-boot.bin
boards.cfg  doc/       MAINTAINERS  net/          snapshot.commit  u-boot.lds
common/     drivers/   MAKEALL*     onenand_ipl/  spl/             u-boot.map
config.mk   examples/  Makefile     patches/      System.map       u-boot.srec

The file we want is right on the top level.

host$ scp u-boot.bin root@beagle:.
host$ ssh -X root@beagle
beagle$ cd /media/mmcblk0p1/; ls -F
MLO*         u-boot.bin.broken*  uEnv.txt*
U-BOOT.BIN*  UIMAGE*             uEnv/

Be sure you are logged into the Beagle via the serial port, rather than using ssh. Otherwise you won't see the boot sequence that appears before the kernel is running.

Here we've changed to the FAT partition which is where u-boot lives. Back it up and install the new one.

beagle$ mv U-BOOT-BIN u-boot-bin.orig
beagle$ mv ~/.u-boot-bin .
beagle$ shutdown -r now

You should now see the new u-boot running if you are logged in via the serial port.

Compile via make

When you use bitbake it sets up all the paths to use the correct cross compilers. You can also build the kernel or u-boot by using make if you set the paths like we did above.

If you haven't already, source the file and cd to the kernel directory and try a make.

host$ source ~/.oe/crossCompileEnv.sh
host$ cd ~/BeagleBoard/oe/build/tmp-angstrom_2010_x-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-omap-psp-2.6.32-r110b+gitr5fc29e7b2a76a64a739f857858ef0b98294aa155/git
host$ make xconfig

(EBC Exercise 13 Configuring the Kernel has details on configuring the kernel.)

To make the kernel run

host$ make uImage

Now, follow the instructions above to install your freshly compiled kernel.

Getting the A6A Kernel

beagle$ cat /etc/angstrom-build-info 
Configured Openembedded layers:
meta-angstrom     = angstrom-v2012.05-yocto1.2:a029f5f5d19f788e2ab17227f35350ff5b6ca125
meta-oe           
toolchain-layer   
meta-efl          
meta-gpe          
meta-gnome        
meta-xfce         
meta-initramfs    
meta-multimedia   = denzil:b4488f4c012a64604b28bd2b6e93de411c34466d
meta-opie         = master:efa3892b20a4ef80274e56e5633ebd62c16f9731
meta-java         = master:3386ea6c96096f107f43f282f654e5afa456109e
meta-browser      = master:c47f59df2e723495679c751cbdf6a8c6adec4b6a
meta-mono         = master:83f8233b0498aadb18bf7605c3ba6c71d9e13a3a
meta-kde          = master:5b0882d951cfd71886d423c190faaa7c7f932333
meta-ti           = angstrom-staging:5364d0795bb27c2deb5a4e2df7d2f01ffb394cca
meta-efikamx      = master:2c09a3a780b23448e8a6ca964256ff7f5ccba65d
meta-nslu2        = master:3d9fc951b05b4df476374b6fc3085ebac7f293ee
meta-htc          
meta-nokia        
meta-openmoko     
meta-palm         = master:2b106be01228f64298d6cb338f93088806594344
meta-handheld     = master:1f05a15aceb4c3a19fa070463b58125b5658b2a9
meta-raspberrypi  = denzil:34eef2ea4f5f24630dbb73b386861430167b8431
meta-intel        
meta-sugarbay     
meta-crownbay     
meta-emenlow      
meta-fishriver    
meta-fri2         
meta-jasperforest 
meta-n450         = master:f75f9b6f68473eb0efac802409608f8389be0030
meta              = denzil:b052427a6678b1b696f8c64cf0fdc55e6af86c48 
host$ cd BeagleBoard/oe/sources/meta-ti
host$ git checkout master




thumb‎ Embedded Linux Class by Mark A. Yoder