Difference between revisions of "EBC Exercise 08a Cross-Compiling"

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'''This page isn't finished yet, please wait before doing it.'''
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[[Category:ECE497]]
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[[Category: BeagleBoard]]
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{{YoderHead}}
  
This class is about developing software for embedded Linux. The eLinux site [[http://elinux.org/Main_Page]] is a good source for embedded Linux in general.  There are many on going embedded efforts going on many platforms. Poke around the site a while to get a feel for what's happening.
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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_4.4]] you learned how to download and install the cross compilers and the source for kernel and u-boot. Now we'll use those tools.
  
We are going to use the Ångström Distribution [[http://www.angstrom-distribution.org]]It's available many platforms. Look around the site, you may recognize some of them.
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== Cross compiling Hello World ==
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Normally when you compile you compile on the machine that will run the code.  You can compile and run on the Bone, but sometimes (like when compiling the kernel) it's better to use a more powerful machine for the compilingFirst we'll compile ''helloWorld.c'' on the host computer and run it there, then we'll cross compile it on the host to run on the Bone.
  
Instructions for building Ångström are given here [[http://www.angstrom-distribution.org/building-angstrom]]; however I'm going to present a Beagle-tuned version of those instructions on this page.
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If you've set up your git repository you will find it in '''helloWorld.c''' when you do a''' git pull'''.  Compile and run it on your host to be sure it works.
  
== Step 1 - get Open Embedded metadata ==
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host$ '''gcc helloWorld.c'''
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host$ '''file a.out'''
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a.out: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked,
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interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0,
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BuildID[sha1]=049e80612d5735fda0966f6e23c637d345447f49, not stripped
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host$ '''./a.out'''
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Hello, World! Main is executing at 0x55f7f41f96aa
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This address (0x7ffd98d0ebd0) is in our stack frame
 +
This address (0x55f7f43fa018) is in our bss section
 +
This address (0x55f7f43fa010) is in our data section
  
First install <code>git</code> by running the following on your host computer.
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Now that you know it's working, let's cross compile it. First figure out what version of the cross compiler was loaded.
<pre>
 
sudo apt-get install git-core
 
</pre>
 
  
Then run the following to load the meta data.
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host$ '''cd BeagleBoard/bb-kernel/dl'''
<pre>
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host$ '''ls'''
export OETREE="${HOME}/oe"
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gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabihf
mkdir -p ${OETREE} && cd ${OETREE}
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gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabihf.tar.xz
git clone git://git.openembedded.org/openembedded.git openembedded
 
cd openembedded
 
git checkout origin/stable/2009 -b stable/2009
 
</pre>
 
The first git transfers some 336,000 object and takes about 18 minutes with the network running at 600 some KiB/s. Keep an eye on it, mine stopped about 23% in and I had to restart it. The second git takes almost no time.
 
  
Now run the following to update the metadata:
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Here we see two versions of the compiler have been loadedLet's pick the newer one.
<pre>
 
cd ${OETREE}/openembedded
 
git pull
 
</pre>
 
You've created a directory called <code>oe</code>.  Go explore around it to see what is there.  Be sure to look in <code>oe/openembedded/recipes</code>.  These folders contain instructions on where to get and how to build various things.  Look in <code>recipes/Linux</code>.  Here are instructions for building various Linux kernelsWe'll be using <code>linux-omap-2.6.*</code>.  What's the highest version you can find?
 
  
== Step 2 - Setting up for the BeagleBoard ==
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Now set the paths to find the cross-compiler. Put the following in a file, call it '''~/crossCompileEnv.sh'''.
  
We need a small script to setup the environment, so download <code>source-me.txt</code> [[http://www.rose-hulman.edu/~yoder/eLinux/files/source-me.txt] to ${OETREE}.
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export ARCH=arm
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export CROSS_COMPILE=arm-linux-gnueabihf-
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export PATH=$PATH:~/BeagleBoard/bb-kernel/dl/gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabihf/bin
  
Now let's setup <code>local.conf</code> for our needs:
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Make sure the PATH you use goes to the bin directory where the cross compiler is installed.
<pre>
 
mkdir -p ${OETREE}/build/conf
 
cp ${OETREE}/openembedded/contrib/angstrom/local.conf ${OETREE}/build/conf/
 
</pre>
 
Open <code>${OETREE}/build/conf/local.conf</code> in your favourite editor and add the following to the end of the file.
 
<pre>
 
MACHINE ?= "beagleboard"
 
</pre>
 
  
== Step 3 - Start building ==
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Now ''source'' the file and compile again. (Note: you only have to source once per terminal session.)
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host$ '''source ~/crossCompileEnv.sh'''
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host$ '''${CROSS_COMPILE}gcc helloWorld.c'''
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host$ '''file a.out'''
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a.out: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV),
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dynamically linked, interpreter /lib/ld-linux-armhf.so.3,
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for GNU/Linux 3.2.0, BuildID[sha1]=17ab3588195851d9eb444f70e5069376cae3bdec,
 +
with debug_info, not stripped
  
<pre>
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The '''file''' command tells what's in the file. In this case we have an ARM executable.  Success!  Now copy to your Beagle and run
# set environment variables
 
source source-me.txt
 
  
#Go to the OE tree
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host$ '''scp a.out debian@192.168.7.2:.'''
cd ${OETREE}/openembedded
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host$ '''ssh debian@192.168.7.2 ./a.out'''
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Hello, World! Main is executing at 0x103d5
 +
This address (0xbeb83c54) is in our stack frame
 +
This address (0x21030) is in our bss section
 +
This address (0x21028) is in our data section
  
#Make sure it's up to date
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The '''scp''' copies ''a.out'' to the beagle and the '''ssh''' runs the ''a.out'' on the beagle. Notice the addresses are very different from the host version.
git pull --rebase
 
  
#Start building
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{{YoderFoot}}
bikebake nano
 
</pre>
 
 
 
# you can specify machine on the cmdline:
 
MACHINE=yourmachine bitbake base-image ; MACHINE=yourmachine bitbake console-image x11-image
 
 
 
# If you have set it in local.conf you can do:
 
bitbake base-image ; bitbake console-image x11-image
 
 
 
[[Category:ECE597]]
 

Latest revision as of 11:21, 20 September 2019

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_4.4 you learned how to download and install the cross compilers and the source for kernel and u-boot. Now we'll use those tools.

Cross compiling Hello World

Normally when you compile you compile on the machine that will run the code. You can compile and run on the Bone, but sometimes (like when compiling the kernel) it's better to use a more powerful machine for the compiling. First we'll compile helloWorld.c on the host computer and run it there, then we'll cross compile it on the host to run on the Bone.

If you've set up your git repository you will find it in helloWorld.c when you do a git pull. Compile and run it on your host to be sure it works.

host$ gcc helloWorld.c
host$ file a.out
a.out: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked,
interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0,
BuildID[sha1]=049e80612d5735fda0966f6e23c637d345447f49, not stripped
host$ ./a.out
Hello, World! Main is executing at 0x55f7f41f96aa
This address (0x7ffd98d0ebd0) is in our stack frame
This address (0x55f7f43fa018) is in our bss section
This address (0x55f7f43fa010) is in our data section

Now that you know it's working, let's cross compile it. First figure out what version of the cross compiler was loaded.

host$ cd BeagleBoard/bb-kernel/dl
host$ ls
gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabihf
gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabihf.tar.xz

Here we see two versions of the compiler have been loaded. Let's pick the newer one.

Now set the paths to find the cross-compiler. Put the following in a file, call it ~/crossCompileEnv.sh.

export ARCH=arm
export CROSS_COMPILE=arm-linux-gnueabihf-
export PATH=$PATH:~/BeagleBoard/bb-kernel/dl/gcc-arm-8.3-2019.03-x86_64-arm-linux-gnueabihf/bin

Make sure the PATH you use goes to the bin directory where the cross compiler is installed.

Now source the file and compile again. (Note: you only have to source once per terminal session.)

host$ source ~/crossCompileEnv.sh
host$ ${CROSS_COMPILE}gcc helloWorld.c
host$ file a.out
a.out: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV),
dynamically linked, interpreter /lib/ld-linux-armhf.so.3,
for GNU/Linux 3.2.0, BuildID[sha1]=17ab3588195851d9eb444f70e5069376cae3bdec,
with debug_info, not stripped

The file command tells what's in the file. In this case we have an ARM executable. Success! Now copy to your Beagle and run

host$ scp a.out debian@192.168.7.2:.
host$ ssh debian@192.168.7.2 ./a.out
Hello, World! Main is executing at 0x103d5
This address (0xbeb83c54) is in our stack frame
This address (0x21030) is in our bss section
This address (0x21028) is in our data section

The scp copies a.out to the beagle and the ssh runs the a.out on the beagle. Notice the addresses are very different from the host version.




thumb‎ Embedded Linux Class by Mark A. Yoder