Android

Mesa hardware drivers can be built for Android one of two ways: built into the Android OS using the ndk-build build system on older versions of Android, or out-of-tree using the Meson build system and the Android NDK.

The ndk-build build system has proven to be hard to maintain, as one needs a built Android tree to build against, and it has never been tested in CI. The Meson build system flow is frequently used by Chrome OS developers for building and testing Android drivers.

When building llvmpipe or lavapipe for Android the ndk-build workflow is also used, but there are additional steps required to add the driver to the Android OS image.

Building using the Android NDK

Download and install the NDK using whatever method you normally would. Then, create your Meson cross file to use it, something like this ~/.local/share/meson/cross/android-aarch64 file:

[binaries]
ar = 'NDKDIR/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ar'
c = ['ccache', 'NDKDIR/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android29-clang']
cpp = ['ccache', 'NDKDIR/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android29-clang++', '-fno-exceptions', '-fno-unwind-tables', '-fno-asynchronous-unwind-tables', '-static-libstdc++']
c_ld = 'lld'
cpp_ld = 'lld'
strip = 'NDKDIR/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-strip'
# Android doesn't come with a pkg-config, but we need one for Meson to be happy not
# finding all the optional deps it looks for.  Use system pkg-config pointing at a
# directory we get to populate with any .pc files we want to add for Android
pkg-config = ['env', 'PKG_CONFIG_LIBDIR=NDKDIR/pkgconfig', '/usr/bin/pkg-config']

[host_machine]
system = 'android'
cpu_family = 'aarch64'
cpu = 'armv8'
endian = 'little'

Now, use that cross file for your Android build directory (as in this one cross-compiling the turnip driver for a stock Pixel phone)

meson setup build-android-aarch64 \
    --cross-file android-aarch64 \
    -Dplatforms=android \
    -Dplatform-sdk-version=26 \
    -Dandroid-stub=true \
    -Dgallium-drivers= \
    -Dvulkan-drivers=freedreno \
    -Dfreedreno-kmds=kgsl
meson compile -C build-android-aarch64

Replacing Android drivers on stock Android

The vendor partition with the drivers is normally mounted from a read-only disk image on /vendor. To be able to replace them for driver development, we need to unlock the device and remount /vendor read/write.

adb disable-verity
adb reboot
adb remount -R
adb remount

Now you can replace drivers as in:

adb push build-android-aarch64/src/freedreno/vulkan/libvulkan_freedreno.so /vendor/lib64/hw/vulkan.sdm710.so

Note this command doesn’t quite work because libvulkan wants the SONAME to match. You can use patchelf to fix this:

cp build-android-aarch64/src/freedreno/vulkan/libvulkan_freedreno.so /tmp/vulkan.sdm710.so
patchelf --set-soname vulkan.sdm710.so /tmp/vulkan.sdm710.so
adb push /tmp/vulkan.sdm710.so /vendor/lib64/hw/

Replacing Android drivers on Chrome OS

Chrome OS’s ARC++ is an Android container with hardware drivers inside of it. The vendor partition with the drivers is normally mounted from a read-only squashfs image on disk. For doing rapid driver development, you don’t want to regenerate that image. So, we’ll take the existing squashfs image, copy it out on the host, and then use a bind mount instead of a loopback mount so we can update our drivers using scp from outside the container.

On your device, you’ll want to make / read-write. ssh in as root and run:

crossystem dev_boot_signed_only=0
/usr/share/vboot/bin/make_dev_ssd.sh --remove_rootfs_verification --partitions 4
reboot

Then, we’ll switch Android from using an image for /vendor to using a bind-mount from a directory we control.

cd /opt/google/containers/android/
mkdir vendor-ro
mount -o loop vendor.raw.img vendor-ro
cp -a vendor-ro vendor-rw
emacs config.json

In the config.json, you want to find the block for /vendor and change it to:

{
    "destination": "/vendor",
    "type": "bind",
    "source": "/opt/google/containers/android/vendor-rw",
    "options": [
        "bind",
        "rw"
    ]
},

Now, restart the UI to do a full reload:

restart ui

At this point, your android container is restarted with your new bind-mount /vendor, and if you use android-sh to shell into it then the mount command should show:

/dev/root on /vendor type ext2 (rw,seclabel,relatime)

Now, replacing your DRI driver with a new one built for Android should be a matter of:

scp msm_dri.so $HOST:/opt/google/containers/android/vendor-rw/lib64/dri/

You can do your build of your DRI driver using emerge-$BOARD arc-mesa-freedreno (for example) if you have a source tree with ARC++, but it should also be possible to build using the NDK as described above. There are currently rough edges with this, for example the build will require that you have your arc-libdrm build available to the NDK, assuming you’re building anything but the Freedreno Vulkan driver for KGSL. You can mostly put things in place with:

scp $HOST:/opt/google/containers/android/vendor-rw/lib64/libdrm.so \
    NDKDIR/sysroot/usr/lib/aarch64-linux-android/lib/

ln -s \
    /usr/include/xf86drm.h \
    /usr/include/libsync.h \
    /usr/include/libdrm \
    NDKDIR/sysroot/usr/include/

It seems that new invocations of an application will often reload the DRI driver, but depending on the component you’re working on you may find you need to reload the whole Android container. To do so without having to log in to Chrome again every time, you can just kill the container and let it restart:

kill $(cat /run/containers/android-run_oci/container.pid )

Adding out-of-tree drivers to Android OS image

When building your own Android OS images it’s possible to add drivers built out of tree directly into the OS image. For running llvmpipe and lavapipe on Android this step is required to ensure Android is able to load the drivers correctly.

The following steps provide and example for building the android cuttlefish image following the official Android documentation from https://source.android.com/docs/setup

When building llvmpipe or lavapipe for Android, it is required to do this so that the permissions for accessing the library are set correctly.

Following the Android documentation, we can run the following commands

repo init -b main -u https://android.googlesource.com/platform/manifest
repo sync -c -j8

source build/envsetup.sh
lunch aosp_cf_x86_64_phone-trunk_staging-userdebug

Be aware that the sync command can take a long time to run as it will download all of the source code. This will set up the aosp_cf_x86_64_phone-trunk_staging-userdebug build target for Android. Please note that the x86_64 cuttlefish target will require you to build mesa for 32bit and 64bit. Next we need to copy the build driver libraries into the source tree of Android and patch the binary names.

mkdir prebuilts/mesa
mkdir prebuilts/mesa/x86_64
mkdir prebuilts/mesa/x86
cp ${INSTALL_PREFIX_64}/lib/libEGL.so prebuilts/mesa/x86_64/
cp ${INSTALL_PREFIX_64}/lib/libglapi.so prebuilts/mesa/x86_64/
cp ${INSTALL_PREFIX_64}/lib/libgallium_dri.so prebuilts/mesa/x86_64/
cp ${INSTALL_PREFIX_64}/lib/libGLESv1_CM.so  prebuilts/mesa/x86_64/
cp ${INSTALL_PREFIX_64}/lib/libGLESv2.so  prebuilts/mesa/x86_64/
cp ${INSTALL_PREFIX_64}/lib/libvulkan_lvp.so prebuilts/mesa/x86_64/
cp ${INSTALL_PREFIX_32}/lib/libEGL.so prebuilts/mesa/x86
cp ${INSTALL_PREFIX_32}/lib/libglapi.so prebuilts/mesa/x86
cp ${INSTALL_PREFIX_32}/lib/libgallium_dri.so prebuilts/mesa/x86/
cp ${INSTALL_PREFIX_32}/lib/libGLESv1_CM.so  prebuilts/mesa/x86
cp ${INSTALL_PREFIX_32}/lib/libGLESv2.so  prebuilts/mesa/x86
cp ${INSTALL_PREFIX_32}/lib/libvulkan_lvp.so prebuilts/mesa/x86

patchelf --set-soname libEGL_lp.so prebuilts/mesa/x86_64/libEGL.so
patchelf --set-soname libGLESv1_CM_lp.so prebuilts/mesa/x86_64/libGLESv1_CM.so
patchelf --set-soname libGLESv2_lp.so prebuilts/mesa/x86_64/libGLESv2.so
patchelf --set-soname vulkan.lvp.so prebuilts/mesa/x86_64/libvulkan_lvp.so
patchelf --set-soname libEGL_lp.so prebuilts/mesa/x86/libEGL.so
patchelf --set-soname libGLESv1_CM_lp.so prebuilts/mesa/x86/libGLESv1_CM.so
patchelf --set-soname libGLESv2_lp.so prebuilts/mesa/x86/libGLESv2.so
patchelf --set-soname vulkan.lvp.so prebuilts/mesa/x86/libvulkan_lvp.so

We then need to create an prebuilts/mesa/Android.bp build file to include the libraries in the build.

cc_prebuilt_library_shared {
    name: "libglapi",
    arch: {
        x86_64: {
            srcs: ["x86_64/libglapi.so"],
        },
        x86: {
            srcs: ["x86/libglapi.so"],
        },
    },
    strip: {
        none: true,
    },
    relative_install_path: "egl",
    shared_libs: ["libc", "libdl", "liblog", "libm"],
    vendor: true
}

cc_prebuilt_library_shared {
    name: "libgallium_dri",
    arch: {
        x86_64: {
            srcs: ["x86_64/libgallium_dri.so"],
        },
        x86: {
            srcs: ["x86/libgallium_dri.so"],
        },
    },
    strip: {
        none: true,
    },
    relative_install_path: "egl",
    shared_libs: ["libc", "libdl", "liblog", "libm"],
    check_elf_files: false,
    vendor: true
}

cc_prebuilt_library_shared {
    name: "libEGL_lp",
    arch: {
        x86_64: {
            srcs: ["x86_64/libEGL.so"],
        },
        x86: {
            srcs: ["x86/libEGL.so"],
        },
    },
    strip: {
        none: true,
    },
    relative_install_path: "egl",
    shared_libs: ["libc", "libdl", "liblog", "libm", "libcutils", "libdrm", "libhardware", "liblog", "libnativewindow", "libsync"],
    check_elf_files: false,
    vendor: true
}

cc_prebuilt_library_shared {
    name: "libGLESv1_CM_lp",
    arch: {
        x86_64: {
            srcs: ["x86_64/libGLESv1_CM.so"],
        },
        x86: {
            srcs: ["x86/libGLESv1_CM.so"],
        },
    },
    strip: {
        none: true,
    },
    relative_install_path: "egl",
    shared_libs: ["libc", "libdl", "liblog", "libm"],
    check_elf_files: false,
    vendor: true
}

cc_prebuilt_library_shared {
    name: "libGLESv2_lp",
    arch: {
        x86_64: {
            srcs: ["x86_64/libGLESv2.so"],
        },
        x86: {
            srcs: ["x86_64/libGLESv2.so"],
        },
    },
    strip: {
        none: true,
    },
    relative_install_path: "egl",
    shared_libs: ["libc", "libdl", "liblog", "libm"],
    check_elf_files: false,
    vendor: true
}

cc_prebuilt_library_shared {
    name: "vulkan.lvp",
    arch: {
        x86_64: {
            srcs: ["x86_64/libvulkan_lvp.so"],
        },
        x86: {
            srcs: ["x86/libvulkan_lvp.so"],
        },
    },
    strip: {
        none: true,
    },
    relative_install_path: "hw",
    shared_libs: ["libc", "libdl", "liblog", "libm", "libcutils", "libdrm", "liblog", "libnativewindow", "libsync", "libz"],
    vendor: true
}

Next we need to update the device configuration to include the libraries in the build, as well as set the appropriate system properties. We can create the file device/google/cuttlefish/shared/mesa/device_vendor.mk

PRODUCT_SOONG_NAMESPACES += prebuilts/mesa
PRODUCT_PACKAGES += libglapi \
                    libGLESv1_CM_lp \
                    libGLESv2_lp \
                    libEGL_lp \
                    libgallium_dri.so \
                    vulkan.lvp
PRODUCT_VENDOR_PROPERTIES += \
        ro.hardware.egl=lp \
        ro.hardware.vulkan=lvp \
        mesa.libgl.always.software=true \
        mesa.android.no.kms.swrast=true \
        debug.hwui.renderer=opengl \
        ro.gfx.angle.supported=false \
        debug.sf.disable_hwc_vds=1 \
        ro.vendor.hwcomposer.mode=client

Also the file device/google/cuttlefish/shared/mesa/BoardConfig.mk

BOARD_VENDOR_SEPOLICY_DIRS += \
        device/google/cuttlefish/shared/mesa/sepolicy

Next the file device/google/cuttlefish/shared/mesa/sepolicy/file_contexts

/vendor/lib(64)?/egl/libEGL_lp\.so u:object_r:same_process_hal_file:s0
/vendor/lib(64)?/egl/libGLESv1_CM_lp\.so u:object_r:same_process_hal_file:s0
/vendor/lib(64)?/egl/libGLESv2_lp\.so u:object_r:same_process_hal_file:s0
/vendor/lib(64)?/libglapi\.so u:object_r:same_process_hal_file:s0
/vendor/lib(64)?/libgallium_dri\.so u:object_r:same_process_hal_file:s0
/vendor/lib(64)?/hw/vulkan\.lvp\.so u:object_r:same_process_hal_file:s0

After creating these files we need to modify the existing config files to include these build files. First we modify device/google/cuttlefish/shared/phone/device_vendor.mk to add the below code in the spot where other device_vendor files are included.

$(call inherit-product, device/google/cuttlefish/shared/mesa/device_vendor.mk)

Lastly we modify device/google/cuttlefish/vsoc_x86_64/BoardConfig.mk to include the following line where the other BoardConfig files are included

-include device/google/cuttlefish/shared/mesa/BoardConfig.mk

Then we are set to continue following the official instructions to build the cuttlefish target and run it in the cuttlefish emulator.