Joe Chung
Monmouth U. Homepage

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====== Compile And Run The Android Goldfish Kernel ======

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You are largely following an online tutorial at [[http://blog.markloiseau.com/2012/07/how-to-compile-the-android-goldfish-emulator-kernel/|blog.markloiseau.com]] on your assigned lab machine.

__For long Terminal commands, I recommend copying and pasting from this page to the Terminal.
__

You can do Parts 1 and 2 at the same time in different Terminals.

===== Part 1. Download kernel build environment (prebuilt C compiler) =====

<code>
  cd /usr/local/android/sdk

  mkdir -p prebuilt/linux-x86/toolchain

  cd prebuilt/linux-x86/toolchain

  git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6
</code>

===== Part 2. Download android kernel =====

<code>
  cd /usr/local/android/sdk

  mkdir -p src/kernel

  cd src/kernel

  git clone https://android.googlesource.com/kernel/goldfish
</code>

===== Part 3. Set up android kernel source =====

You may have noticed that after the big download of Part 2, there appears to be nothing in the ''goldfish'' directory. Actually, there's a hidden ''.git'' directory in there. Don't erase it. It contains a local [[https://en.wikipedia.org/wiki/Git_(software)|git]] repository of the kernel source. We need to "checkout" a working copy of the kernel source from the repository before we can work with it. Run these commands. (The '#' lines are just comments.)

<code>
  cd /usr/local/android/sdk/src/kernel/goldfish

  # OPTIONAL; shows hidden .git directory
  ls -a 

  git branch -a

  git checkout -t origin/android-goldfish-2.6.29 -b goldfish

  # Shows the working copy of kernel source that was checked out.
  ls -a
</code>

===== Part 4: Set build environment variables and build kernel =====

<code>
  # Make commands in kernel build environment available in the current running shell:
  export PATH=/usr/local/android/sdk/prebuilt/linux-x86/toolchain/arm-eabi-4.6/bin:$PATH

  # OPTIONAL; see what the PATH environment variable contains:
  echo $PATH

  # Set up architecture-specific variables:
  export ARCH=arm
  export SUBARCH=arm
  export CROSS_COMPILE=arm-eabi-

  # Create a configuration file (.config) for the kernel we're about to compile:
  make goldfish_armv7_defconfig

  # OPTIONAL; see the main Makefile for the kernel build
  less Makefile # press 'q' to quit the 'less' program

  # Process the Makefile to build the kernel; the 'time' command will tell us how long the
  # compile process took.
  time make
  
  # Assuming no errors occurred above, the compiled kernel image will be the zImage
  # file located in /usr/local/android/sdk/src/kernel/goldfish/arch/arm/boot directory.
  ls -l arch/arm/boot/zImage
</code>

===== Part 5: Run an arm-based AVD with the arm kernel we just compiled =====

This part assumes that you have gone through all steps to [[http://rockhopper.monmouth.edu/cs/jchung/cs438/cs-438_set_up_virtual_android_environment|set up a virtual Android environment]], particularly that you created an arm-based AVD along with your Intel Atom-based AVD.

<code>
  # Assumes you have changed directory (cd) to the
  # /usr/local/android/sdk/src/kernel/goldfish directory;
  # Copy the kernel to the /usr/local/android/sdk/src/kernel/goldfish directory for future use:
  cp  arch/arm/boot/zImage  zImage-arm-goldfish-2.6.29

  # Run your arm-based AVD with the new kernel;
  # If your arm-based AVD has a different name than "TestAVDarm" substitute that name below:
  emulator -kernel zImage-arm-goldfish-2.6.29 -avd TestAVDarm
</code>

  * This should start the AVD with the ''zImage-arm-goldfish-2.6.29'' kernel. To verify, in the AVD go to "Settings" and select "About phone" and look at "Kernel version".

  * __While a AVD is running__, you can run ''adb shell'' in another Terminal. This will open the [[https://en.wikipedia.org/wiki/Android_Debug_Bridge|Android Debug Bridge]] command prompt on the AVD. You'll see a ''#'' command prompt in which you can run a variety of useful commands. For now, just run ''cat /proc/version'' to see more information about the kernel.

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