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

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m (Cross-compiling Hello World: Fixed some typos)
m (Updated for 3.8)
Line 13: Line 13:
  
 
  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 28: Line 32:
 
  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

Revision as of 16:12, 27 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 ~/.oe/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 ~/.oe/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