Android — The Mesa 3D Graphics Library latest documentation

# 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.

## Preparing offline compilers

For cross-compiling the nvk driver, mesa_clc compiler binary needs to be prepared first:

    meson setup build-compiler \
        -Dprefix=/tmp/mesa-compiler \
        -Dbuildtype=release \
        -Dstrip=true \
        -Dplatforms= \
        -Dgallium-drivers= \
        -Dvulkan-drivers= \
        -Dmesa-clc=enabled \
        -Dinstall-mesa-clc=true
    meson install -C build-compiler
    export PATH=/tmp/mesa-compiler/bin:$PATH

For panvk, `-Dtools=panfrost -Dinstall-precomp-compiler=true` is additionally needed.

## 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:

    [constants]
    ndk_path = <absolute path to NDK>

    [binaries]
    ar = ndk_path / 'toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ar'
    c = ['ccache', ndk_path / 'toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android34-clang']
    cpp = ['ccache', ndk_path / 'toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android34-clang++', '-fno-exceptions', '-fno-unwind-tables', '-fno-asynchronous-unwind-tables', '--start-no-unused-arguments', '-static-libstdc++', '--end-no-unused-arguments']
    c_ld = 'lld'
    cpp_ld = 'lld'
    strip = ndk_path / 'toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-strip'

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

For nvk, below rust toolchain preparation and cross file additions are needed:

    rustup target add aarch64-linux-android

    [properties]
    bindgen_clang_arguments = ['-target', 'aarch64-linux-android', '--sysroot', ndk_path / 'toolchains/llvm/prebuilt/linux-x86_64/sysroot']

    [binaries]
    rust = ['rustc', '--target', 'aarch64-linux-android']

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=34 \
        -Dandroid-stub=true \
        -Dandroid-libbacktrace=disabled \
        -Degl=disabled \
        -Dgallium-drivers= \
        -Dvulkan-drivers=freedreno \
        -Dfreedreno-kmds=kgsl
    meson compile -C build-android-aarch64

For drm drivers, `-Dallow-fallback-for=libdrm` is needed. Besides, `-Dallow-fallback-for=libdrm -Dmesa-clc=system` is needed by nvk, and `-Dprecomp-compiler=system` is additionally needed by panvk.

## 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/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/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: "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.

## Android System Properties

Android (generally) uses system properties rather than environment variables to control Mesa/Gallium behavior, although there are some exceptions to this for Android app developers.

With the `os_get_option()` helper, the environment variable names are automatically translated to the corresponding system property name by:

- converting UPPER case to lower case

- replacing `_` with `.`

- adding the `mesa.` prefix to `<property_name>` if it’s not present already

- and then querying the system property name with the following prefixes, in order:

  > 1. `debug.<property_name>`

  > 2. `vendor.<property_name>`

  > 3. `<property_name>`

For example, `LIBGL_DEBUG` will be queried as:

1. `debug.mesa.libgl.debug`

2. `vendor.mesa.libgl.debug`

3. `mesa.libgl.debug`

This allows for default `vendor.` / `mesa.` properties to be overridden by users at run-time with `debug.` values.

System properties can be queried with:

    $ adb shell getprop <property_name>

System properties can be set with:

    $ adb shell setprop <property_name> <value>

For example:

    $ adb shell setprop debug.mesa.libgl.debug verbose
    $ adb shell getprop debug.mesa.libgl.debug
    verbose

NOTE: Any driver that wishes to support Android system properties should replace any calls to `getenv()` with `os_get_option()`, which automatically handles both environment variables and Android system properties.

### Android App Developers

Android app developers have two options to control Mesa behavior on un-rooted devices:

- Environment variables, using the wrap shell script

  - https://developer.android.com/ndk/guides/wrap-script.html

- `debug.<property_name>` system properties

App developers with access to rooted devices can also use `vendor.` and `mesa.` values, although `debug.` prefixes are recommended.

While the system properties values are used for each app invocation once set, they do not persist across device reboots.

### Android Driver Developers

Android driver developers have three options to control Mesa behavior on devices with `root` access:

1. `debug.<property_name>`

2. `vendor.<property_name>`

3. `<property_name>`

The `debug.` prefix can be used without `root`, while `vendor.` and `mesa.` prefixes require `root`.

Any of the values can be set in the device’s makefile to control Mesa behavior, although `vendor.` and `mesa.` are typically used for this purpose.

While the system properties values are used for each app invocation once set at runtime, they do not persist across device reboots if configured with `setprop`.