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

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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]] you learned how to download and install the cross-compilers and the source for kernel and u-boot. Now we'll use those tools.
 
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.
 
  
 
== Cross-compiling Hello World ==
 
== Cross-compiling Hello World ==
 +
This shows how to cross-compile with compiler loaded with
 +
 +
host$ '''sudo apt-get install -y git lzop gcc-arm-linux-gnueabi uboot-mkimage'''
  
 
Listing 2-4 on page 29 of the text is an embedded version of Hello World. 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.
 
Listing 2-4 on page 29 of the text is an embedded version of Hello World. 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$ '''gcc helloWorld.c'''
 +
host$ '''file a.out'''
 +
a.out: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
 +
  dynamically linked (uses shared libs), for GNU/Linux 2.6.24,
 +
  BuildID[sha1]=0x357e34e90f7c32d414368d69cc06d0aed59acf1c, not stripped
 
  host$ '''./a.out'''
 
  host$ '''./a.out'''
 
  Hello, World! Main is executing at 0x400524
 
  Hello, World! Main is executing at 0x400524
Line 18: Line 23:
 
  This address (0x601020) is in our data section
 
  This address (0x601020) is in our data section
  
Now that you know it's working, let's cross compile it. First set the paths to find the cross-compilers. Put the following in a file, call it ~/.oe/'''crossCompileEnv.sh'''. Make sure the path is correct for your system. This is for a 32-bit linux.  
+
Now that you know it's working, let's cross compile it. First set the paths to find the cross-compiler. Put the following in a file, call it '''~/crossCompileEnv.sh'''.
  
# add cross tools to your path
 
export ARM_TOOLCHAIN_PATH=~/BeagleBoard/oe/build/tmp-angstrom_v2012_05-eglibc/sysroots/i686-linux/usr/bin/armv7a-angstrom-linux-gnueabi
 
PATH=$PATH:$ARM_TOOLCHAIN_PATH/..
 
PATH=$ARM_TOOLCHAIN_PATH:$PATH 
 
 
  export ARCH=arm
 
  export ARCH=arm
  export CROSS_COMPILE=arm-angstrom-linux-gnueabi-
+
  export CROSS_COMPILE=arm-linux-gnueabi-
 
+
Here it is for 64-bit
+
 
+
# add cross tools to your path
+
export ARM_TOOLCHAIN_PATH=~/BeagleBoard/oe/build/tmp-angstrom_v2012_05-eglibc/sysroots/x86_64-linux/usr/bin/armv7a-angstrom-linux-gnueabi
+
PATH=$PATH:$ARM_TOOLCHAIN_PATH/..
+
PATH=$ARM_TOOLCHAIN_PATH:$PATH 
+
export ARCH=arm
+
export CROSS_COMPILE=arm-angstrom-linux-gnueabi-
+
  
 
Now ''source'' the file and compile again. (Note: you only have to source once per terminal session.)
 
Now ''source'' the file and compile again. (Note: you only have to source once per terminal session.)
  host$ '''source ~/.oe/crossCompileEnv.sh'''
+
  host$ '''source ~/crossCompileEnv.sh'''
 
  host$ '''${CROSS_COMPILE}gcc helloWorld.c'''
 
  host$ '''${CROSS_COMPILE}gcc helloWorld.c'''
 
  host$ '''file a.out'''
 
  host$ '''file a.out'''
  a.out: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.16, not stripped
+
  a.out: ELF 32-bit LSB executable, ARM, version 1 (SYSV),  
 +
  dynamically linked (uses shared libs), for GNU/Linux 2.6.31,
 +
  BuildID[sha1]=0x10182364352b9f3cb15d1aa61395aeede11a52ad, 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
 
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
Line 51: Line 45:
 
  This address (0x10648) is in our data section
 
  This address (0x10648) 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 address are very different from the host version.
+
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.
 
+
== Finding the Kernel and Installing It ==
+
 
+
After doing [[EBC Exercise 08 Installing Development Tools]] 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 '''.git'''s 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'''
+
Error (''Someone paste the the actual error message here.  I don't get it any more'')
+
 
+
So what repository has the tag '''5364d0795bb27c2deb5a4e2df7d2f01ffb394cca'''?  Try google.
+
 
+
Change to the kernel directory. It's one of the paths that leads to the '''uImage''' found above.
+
host$ '''cd ~/BeagleBoard/oe/build/tmp-angstrom_v2012_05-eglibc/work/beagleboard-angstrom-linux-gnueabi/linux-mainline-3.2.18-r121b/git'''
+
 
+
Here look for all the '''.git''' directories
+
host$ '''find . -name .git'''
+
 
+
The 40 digit hex number is the SHA-1 hash (or haah tag, or tag) that was assigned for the git commit that was used in building the 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.
+
 
+
== 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'''
+
  
 
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Revision as of 01:26, 28 May 2013

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.

Cross-compiling Hello World

This shows how to cross-compile with compiler loaded with

host$ sudo apt-get install -y git lzop gcc-arm-linux-gnueabi uboot-mkimage

Listing 2-4 on page 29 of the text is an embedded version of Hello World. 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 32-bit LSB executable, Intel 80386, version 1 (SYSV), 
 dynamically linked (uses shared libs), for GNU/Linux 2.6.24, 
 BuildID[sha1]=0x357e34e90f7c32d414368d69cc06d0aed59acf1c, not stripped
host$ ./a.out
Hello, World! Main is executing at 0x400524
This address (0x7fff8260bdf8) is in our stack frame
This address (0x601038) is in our bss section
This address (0x601020) is in our data section

Now that you know it's working, let's cross compile it. First 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-gnueabi-

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, version 1 (SYSV), 
 dynamically linked (uses shared libs), for GNU/Linux 2.6.31, 
 BuildID[sha1]=0x10182364352b9f3cb15d1aa61395aeede11a52ad, 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 root@beagle:.
host$ ssh root@beagle ./a.out
Hello, World! Main is executing at 0x8374
This address (0xbeb32d4c) is in our stack frame
This address (0x10650) is in our bss section
This address (0x10648) 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