| page.title=Building Kernels |
| @jd:body |
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| <div id="qv-wrapper"> |
| <div id="qv"> |
| <h2>In this document</h2> |
| <ol id="auto-toc"> |
| </ol> |
| </div> |
| </div> |
| |
| <p>If you are only interested in the kernel, you may use this guide |
| to download and build the appropriate kernel.</p> |
| <p>The following instructions assume that you have not downloaded all |
| of AOSP. If you have downloaded all of AOSP, you may skip the git |
| clone steps other than the step to download the actual kernel sources.</p> |
| <p>We will use the Pandaboard kernel in all the following examples.</p> |
| <h2 id="figuring-out-which-kernel-to-build">Figuring out which kernel to build</h2> |
| <p>This table lists the name and locations of the kernel sources and binaries: |
| <table> |
| <tr> |
| <th>Device</th> |
| <th>Binary location</th> |
| <th>Source location</th> |
| <th>Build configuration</th> |
| </tr> |
| <tr> |
| <td>hammerhead</td> |
| <td>device/lge/hammerhead-kernel</td> |
| <td>kernel/msm</td> |
| <td>hammerhead_defconfig</td> |
| </tr> |
| <tr> |
| <td>flo</td> |
| <td>device/asus/flo-kernel/kernel</td> |
| <td>kernel/msm</td> |
| <td>flo_defconfig</td> |
| </tr> |
| <tr> |
| <td>deb</td> |
| <td>device/asus/flo-kernel/kernel</td> |
| <td>kernel/msm</td> |
| <td>flo_defconfig</td> |
| </tr> |
| <tr> |
| <td>manta</td> |
| <td>device/samsung/manta/kernel</td> |
| <td>kernel/exynos</td> |
| <td>manta_defconfig</td> |
| </tr> |
| <tr> |
| <td>mako</td> |
| <td>device/lge/mako-kernel/kernel</td> |
| <td>kernel/msm</td> |
| <td>mako_defconfig</td> |
| </tr> |
| <tr> |
| <td>grouper</td> |
| <td>device/asus/grouper/kernel</td> |
| <td>kernel/tegra</td> |
| <td>tegra3_android_defconfig</td> |
| </tr> |
| <tr> |
| <td>tilapia</td> |
| <td>device/asus/grouper/kernel</td> |
| <td>kernel/tegra</td> |
| <td>tegra3_android_defconfig</td> |
| </tr> |
| <tr> |
| <td>maguro</td> |
| <td>device/samsung/tuna/kernel</td> |
| <td>kernel/omap</td> |
| <td>tuna_defconfig</td> |
| </tr> |
| <tr> |
| <td>toro</td> |
| <td>device/samsung/tuna/kernel</td> |
| <td>kernel/omap</td> |
| <td>tuna_defconfig</td> |
| </tr> |
| <tr> |
| <td>panda</td> |
| <td>device/ti/panda/kernel</td> |
| <td>kernel/omap</td> |
| <td>panda_defconfig</td> |
| </tr> |
| <tr> |
| <td>stingray</td> |
| <td>device/moto/wingray/kernel</td> |
| <td>kernel/tegra</td> |
| <td>stingray_defconfig</td> |
| </tr> |
| <tr> |
| <td>wingray</td> |
| <td>device/moto/wingray/kernel </td> |
| <td>kernel/tegra</td> |
| <td>stingray_defconfig</td> |
| </tr> |
| <tr> |
| <td>crespo</td> |
| <td>device/samsung/crespo/kernel</td> |
| <td>kernel/samsung</td> |
| <td>herring_defconfig</td> |
| </tr> |
| <tr> |
| <td>crespo4g</td> |
| <td>device/samsung/crespo/kernel</td> |
| <td>kernel/samsung</td> |
| <td>herring_defconfig</td> |
| </tr> |
| </table> |
| |
| <p>You will want to look at the git log for the kernel binary in the device |
| project that you are interested in.</p> |
| |
| <p>Device projects are of the form device/<vendor>/<name>.</p> |
| <pre><code>$ git clone https://android.googlesource.com/device/ti/panda |
| $ cd panda |
| $ git log --max-count=1 kernel |
| </code></pre> |
| |
| <p>The commit message for the kernel binary contains a partial git log |
| of the kernel sources that were used to build the binary in question. |
| The first entry in the log is the most recent, i.e. the one used to |
| build that kernel. You will need it at a later step.</p> |
| |
| |
| <h2 id="id-version">Identifying kernel version</h2> |
| <p>To determine the kernel version used in a particular system image, run the |
| following command against the kernel file:</p> |
| <pre><code> |
| $ dd if=kernel bs=1 skip=$(LC_ALL=C grep -a -b -o $'\x1f\x8b\x08\x00\x00\x00\x00\x00' kernel | cut -d ':' -f 1) | zgrep -a 'Linux version' |
| </code></pre> |
| <p>For Nexus 5 (hammerhead), this can be accomplished with:</p> |
| <pre><code> |
| $ bzgrep -a 'Linux version' vmlinux.bz2 |
| </code></pre> |
| |
| |
| <h2 id="downloading-sources">Downloading sources</h2> |
| <p>Depending on which kernel you want,</p> |
| <pre><code>$ git clone https://android.googlesource.com/kernel/common.git |
| $ git clone https://android.googlesource.com/kernel/exynos.git |
| $ git clone https://android.googlesource.com/kernel/goldfish.git |
| $ git clone https://android.googlesource.com/kernel/msm.git |
| $ git clone https://android.googlesource.com/kernel/omap.git |
| $ git clone https://android.googlesource.com/kernel/samsung.git |
| $ git clone https://android.googlesource.com/kernel/tegra.git |
| </code></pre> |
| <ul> |
| <li>The <code>goldfish</code> project contains the kernel sources for the emulated |
| platforms.</li> |
| <li>The <code>msm</code> project has the sources for ADP1, ADP2, Nexus One, Nexus 4, |
| and can be used as a starting point for work on Qualcomm MSM chipsets.</li> |
| <li>The <code>omap</code> project is used for PandaBoard and Galaxy Nexus, |
| and can be used as a starting point for work on TI OMAP chipsets.</li> |
| <li>The <code>samsung</code> project is used for Nexus S, |
| and can be used as a starting point for work on Samsung Hummingbird chipsets.</li> |
| <li>The <code>tegra</code> project is for Xoom and Nexus 7, |
| and can be used as a starting point for work on NVIDIA Tegra chipsets.</li> |
| <li>The <code>exynos</code> project has the kernel sources for Nexus 10, |
| and can be used as a starting point for work on Samsung Exynos chipsets.</li> |
| </ul> |
| <h2 id="downloading-a-prebuilt-gcc">Downloading a prebuilt gcc</h2> |
| <p>Ensure that the prebuilt toolchain is in your path.</p> |
| <pre>$ export PATH=$(pwd)/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6/bin:$PATH</pre> |
| |
| or |
| <pre>$ export PATH=$(pwd)/prebuilts/gcc/darwin-x86/arm/arm-eabi-4.6/bin:$PATH</pre> |
| |
| <p>On a linux host, if you don't have an Android source tree, you can download |
| the prebuilt toolchain from: |
| <pre>$ git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6</pre> |
| |
| <h2 id="building">Building</h2> |
| <p>As an example, we would build the panda kernel using the following commands:</p> |
| <pre><code>$ export ARCH=arm |
| $ export SUBARCH=arm |
| $ export CROSS_COMPILE=arm-eabi- |
| $ cd omap |
| $ git checkout <commit_from_first_step> |
| $ make panda_defconfig |
| $ make |
| </code></pre> |
| <p>To build the tuna kernel, you may run the previous commands replacing all |
| instances of "panda" with "tuna".</p> |
| <p> |
| The kernel binary is output as: `arch/arm/boot/zImage` It can be copied |
| into the Android source tree in order to build the matching boot image. |
| </p> |
| <p>Or you can include the <code>TARGET_PREBUILT_KERNEL</code> variable while |
| using <code>make bootimage</code> or any other make command line that builds a |
| boot image.</p> |
| <pre><code> |
| $ export TARGET_PREBUILT_KERNEL=$your_kernel_path/arch/arm/boot/zImage |
| </code></pre> |
| <p>That variable is supported by all devices as it is set up via |
| device/common/populate-new-device.sh</p> |