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.
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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.
  
== Cross-compiling Hello World ==
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== Cross compiling Hello World ==
This shows how to cross-compile with compiler loaded with
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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 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.
  
host$ '''sudo apt-get install -y git lzop gcc-arm-linux-gnueabi uboot-mkimage'''
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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.
 
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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.
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  host$ '''gcc helloWorld.c'''
 
  host$ '''gcc helloWorld.c'''
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host$ '''file a.out'''
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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 19: Line 21:
 
  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-compiler. Put the following in a file, call it ~/.oe/'''crossCompileEnv.sh'''.
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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 ARCH=arm
  export CROSS_COMPILE=arm-linux-gnueabi-
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  export CROSS_COMPILE=arm-linux-gnueabihf-
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export PATH=$PATH:~/BeagleBoard/bb-kernel/dl/gcc-linaro-5.3-2016.02-x86_64_arm-linux-gnueabihf/bin
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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.)
 
Now ''source'' the file and compile again. (Note: you only have to source once per terminal session.)
  host$ '''source ~/.oe/crossCompileEnv.sh'''
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  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
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  a.out: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV),  
 +
  dynamically linked (uses shared libs), for GNU/Linux 2.6.32,
 +
  BuildID[sha1]=b9222cbcee442470c7b89ac294e392a631c82264, 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
  
  host$ '''scp a.out root@beagle:.'''
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  host$ '''scp a.out root@192.168.7.2:.'''
  host$ '''ssh root@beagle ./a.out'''
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  host$ '''ssh root@192.168.7.2 ./a.out'''
 
  Hello, World! Main is executing at 0x8374
 
  Hello, World! Main is executing at 0x8374
 
  This address (0xbeb32d4c) is in our stack frame
 
  This address (0xbeb32d4c) is in our stack frame
Line 39: 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 addresses are very different from the host version.
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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.
  
 
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Latest revision as of 12:02, 20 July 2016

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 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-gnueabihf-
export PATH=$PATH:~/BeagleBoard/bb-kernel/dl/gcc-linaro-5.3-2016.02-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 (uses shared libs), for GNU/Linux 2.6.32, 
 BuildID[sha1]=b9222cbcee442470c7b89ac294e392a631c82264, 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@192.168.7.2:.
host$ ssh root@192.168.7.2 ./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