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      1 page.title=Building Kernels
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     19 <div id="qv-wrapper">
     20   <div id="qv">
     21     <h2>In this document</h2>
     22     <ol id="auto-toc">
     23     </ol>
     24   </div>
     25 </div>
     26 
     27 <p>If you are only interested in the kernel, you may use this guide
     28 to download and build the appropriate kernel.</p>
     29 <p>The following instructions assume that you have not downloaded all
     30 of AOSP.  If you have downloaded all of AOSP, you may skip the git
     31 clone steps other than the step to download the actual kernel sources.</p>
     32 <p>We will use the Pandaboard kernel in all the following examples.</p>
     33 <h2 id="figuring-out-which-kernel-to-build">Figuring out which kernel to build</h2>
     34 <p>This table lists the name and locations of the kernel sources and binaries:
     35 <table>
     36   <tr>
     37     <th>Device</th>
     38     <th>Binary location</th>
     39     <th>Source location</th>
     40     <th>Build configuration</th>
     41   </tr>
     42   <tr>
     43     <td>hammerhead</td>
     44     <td>device/lge/hammerhead-kernel</td>
     45     <td>kernel/msm</td>
     46     <td>hammerhead_defconfig</td>
     47   </tr>
     48   <tr>
     49     <td>flo</td>
     50     <td>device/asus/flo-kernel/kernel</td>
     51     <td>kernel/msm</td>
     52     <td>flo_defconfig</td>
     53   </tr>
     54   <tr>
     55     <td>deb</td>
     56     <td>device/asus/flo-kernel/kernel</td>
     57     <td>kernel/msm</td>
     58     <td>flo_defconfig</td>
     59   </tr>
     60   <tr>
     61     <td>manta</td>
     62     <td>device/samsung/manta/kernel</td>
     63     <td>kernel/exynos</td>
     64     <td>manta_defconfig</td>
     65   </tr>
     66   <tr>
     67     <td>mako</td>
     68     <td>device/lge/mako-kernel/kernel</td>
     69     <td>kernel/msm</td>
     70     <td>mako_defconfig</td>
     71   </tr>
     72   <tr>
     73     <td>grouper</td>
     74     <td>device/asus/grouper/kernel</td>
     75     <td>kernel/tegra</td>
     76     <td>tegra3_android_defconfig</td>
     77   </tr>
     78   <tr>
     79     <td>tilapia</td>
     80     <td>device/asus/grouper/kernel</td>
     81     <td>kernel/tegra</td>
     82     <td>tegra3_android_defconfig</td>
     83   </tr>
     84   <tr>
     85     <td>maguro</td>
     86     <td>device/samsung/tuna/kernel</td>
     87     <td>kernel/omap</td>
     88     <td>tuna_defconfig</td>
     89   </tr>
     90   <tr>
     91     <td>toro</td>
     92     <td>device/samsung/tuna/kernel</td>
     93     <td>kernel/omap</td>
     94     <td>tuna_defconfig</td>
     95   </tr>
     96   <tr>
     97     <td>panda</td>
     98     <td>device/ti/panda/kernel</td>
     99     <td>kernel/omap</td>
    100     <td>panda_defconfig</td>
    101   </tr>
    102   <tr>
    103     <td>stingray</td>
    104     <td>device/moto/wingray/kernel</td>
    105     <td>kernel/tegra</td>
    106     <td>stingray_defconfig</td>
    107   </tr>
    108   <tr>
    109     <td>wingray</td>
    110     <td>device/moto/wingray/kernel </td>
    111     <td>kernel/tegra</td>
    112     <td>stingray_defconfig</td>
    113   </tr>
    114   <tr>
    115     <td>crespo</td>
    116     <td>device/samsung/crespo/kernel</td>
    117     <td>kernel/samsung</td>
    118     <td>herring_defconfig</td>
    119   </tr>
    120   <tr>
    121     <td>crespo4g</td>
    122     <td>device/samsung/crespo/kernel</td>
    123     <td>kernel/samsung</td>
    124     <td>herring_defconfig</td>
    125   </tr>
    126 </table>
    127 
    128 <p>You will want to look at the git log for the kernel binary in the device
    129 project that you are interested in.</p>
    130 
    131 <p>Device projects are of the form device/&lt;vendor&gt;/&lt;name&gt;.</p>
    132 <pre><code>$ git clone https://android.googlesource.com/device/ti/panda
    133 $ cd panda
    134 $ git log --max-count=1 kernel
    135 </code></pre>
    136 
    137 <p>The commit message for the kernel binary contains a partial git log
    138 of the kernel sources that were used to build the binary in question.
    139 The first entry in the log is the most recent, i.e. the one used to
    140 build that kernel. You will need it at a later step.</p>
    141 
    142 
    143 <h2 id="id-version">Identifying kernel version</h2>
    144 <p>To determine the kernel version used in a particular system image, run the
    145 following command against the kernel file:</p>
    146 <pre><code>
    147 $ 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'
    148 </code></pre>
    149 <p>For Nexus 5 (hammerhead), this can be accomplished with:</p>
    150 <pre><code>
    151 $ bzgrep -a 'Linux version' vmlinux.bz2
    152 </code></pre>
    153 
    154 
    155 <h2 id="downloading-sources">Downloading sources</h2>
    156 <p>Depending on which kernel you want,</p>
    157 <pre><code>$ git clone https://android.googlesource.com/kernel/common.git
    158 $ git clone https://android.googlesource.com/kernel/exynos.git
    159 $ git clone https://android.googlesource.com/kernel/goldfish.git
    160 $ git clone https://android.googlesource.com/kernel/msm.git
    161 $ git clone https://android.googlesource.com/kernel/omap.git
    162 $ git clone https://android.googlesource.com/kernel/samsung.git
    163 $ git clone https://android.googlesource.com/kernel/tegra.git
    164 </code></pre>
    165 <ul>
    166 <li>The <code>goldfish</code> project contains the kernel sources for the emulated
    167 platforms.</li>
    168 <li>The <code>msm</code> project has the sources for ADP1, ADP2, Nexus One, Nexus 4,
    169 and can be used as a starting point for work on Qualcomm MSM chipsets.</li>
    170 <li>The <code>omap</code> project is used for PandaBoard and Galaxy Nexus,
    171 and can be used as a starting point for work on TI OMAP chipsets.</li>
    172 <li>The <code>samsung</code> project is used for Nexus S,
    173 and can be used as a starting point for work on Samsung Hummingbird chipsets.</li>
    174 <li>The <code>tegra</code> project is for Xoom and Nexus 7,
    175 and can be used as a starting point for work on NVIDIA Tegra chipsets.</li>
    176 <li>The <code>exynos</code> project has the kernel sources for Nexus 10,
    177 and can be used as a starting point for work on Samsung Exynos chipsets.</li>
    178 </ul>
    179 <h2 id="downloading-a-prebuilt-gcc">Downloading a prebuilt gcc</h2>
    180 <p>Ensure that the prebuilt toolchain is in your path.</p>
    181 <pre>$ export PATH=$(pwd)/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6/bin:$PATH</pre>
    182 
    183 or
    184 <pre>$ export PATH=$(pwd)/prebuilts/gcc/darwin-x86/arm/arm-eabi-4.6/bin:$PATH</pre>
    185 
    186 <p>On a linux host, if you don't have an Android source tree, you can download
    187 the prebuilt toolchain from:
    188 <pre>$ git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6</pre>
    189 
    190 <h2 id="building">Building</h2>
    191 <p>As an example, we would build the panda kernel using the following commands:</p>
    192 <pre><code>$ export ARCH=arm
    193 $ export SUBARCH=arm
    194 $ export CROSS_COMPILE=arm-eabi-
    195 $ cd omap
    196 $ git checkout &lt;commit_from_first_step&gt;
    197 $ make panda_defconfig
    198 $ make
    199 </code></pre>
    200 <p>To build the tuna kernel, you may run the previous commands replacing all
    201 instances of "panda" with "tuna".</p>
    202 <p>
    203 The kernel binary is output as: `arch/arm/boot/zImage` It can be copied
    204 into the Android source tree in order to build the matching boot image.
    205 </p>
    206 <p>Or you can include the <code>TARGET_PREBUILT_KERNEL</code> variable while
    207 using <code>make bootimage</code> or any other make command line that builds a
    208 boot image.</p>
    209 <pre><code>
    210 $ export TARGET_PREBUILT_KERNEL=$your_kernel_path/arch/arm/boot/zImage
    211 </code></pre>
    212 <p>That variable is supported by all devices as it is set up via
    213 device/common/populate-new-device.sh</p>
    214