uwu_kernel configuration reference

Top-level properties

Property	Description
kernel_dir	Kernel source directory relative to the Android source root; required for source builds
prebuilt	Prebuilt kernel path; skips source Kbuild when set
prebuilt_config	Generated .config file; used only with prebuilt
prebuilt_headers	Gzip-compressed kernel UAPI headers archive; used only with prebuilt
prebuilt_modules	Prebuilt kernel modules zip; used only with prebuilt
kernel_arch	Kbuild architecture, such as arm64
image_name	Kernel filename under arch/<arch>/boot; required for source builds
clang_version	Toolchain version under prebuilts/clang/host/linux-x86
clang_path	Custom Clang directory; takes precedence over clang_version
rust_version	Optional Rust toolchain version
clang_triple	Override for the default CLANG_TRIPLE
cross_compile	CROSS_COMPILE value passed to Kbuild
cc / ld	Override for the default C compiler or linker
autofdo_profile	AutoFDO profile path; searches for a GKI profile by default, or set to none to disable
rbe_wrapper	Complete rewrapper command; uses kernel_rbe_cc.sh for compilation when set
make_command	Override for the tree-local make command
build_jobs	Override for Kbuild -j parallelism
make_flags	Variables or arguments passed to all Kbuild invocations
additional_flags	Additional device-specific Kbuild arguments; mainly for migrating TARGET_KERNEL_ADDITIONAL_FLAGS
environment	Additional environment assignments passed to the Kbuild action
srcs	Additional analysis-time inputs; does not replace the source directory dependency

The default Kbuild parallelism is calculated using integer arithmetic: (logical CPU count + 2) * 3 / 2.

If clang_version and rust_version are not explicitly set, uwu_kernel prefers LLVM_AOSP_PREBUILTS_VERSION and RUST_AOSP_PREBUILTS_VERSION exported by envsetup. Clang then falls back to clang-stable. If no Rust version is set, no Rust toolchain path is added.

Each environment entry must use the NAME=value format and becomes a shell environment variable for the Kbuild action. Use make_flags or additional_flags to pass Make variables.

Kconfig

config: {
    defconfig: "gki_defconfig",
    fragments: [
        "vendor/common.config",
        "vendor/device.config",
    ],
    merge_at_once: true,
    overrides: [
        "CONFIG_EXAMPLE=y",
    ],
    lto: "thin",
},

Configuration is processed in this order:

1. initialize .config from defconfig;
2. run olddefconfig;
3. merge fragments sequentially or all at once;
4. modify LTO options according to lto;
5. append overrides;
6. run olddefconfig again.

lto supports none, thin, and full. Verify the final fragment and override results in the generated .config, rather than checking only the source files.

Configuration names without /, and names beginning with vendor/, resolve under:

<kernel_dir>/arch/<config_arch>/configs/<name>

Other valid configuration paths can resolve relative to the Android source root. For example, kernel/vendor/foo.config points to a file under the source root. The x86_64 defconfig directory is still converted to arch/x86/configs.

DTB and DTBO

dtb: {
    enabled: true,
    qcom_merge: true,
    target: "dtbs",
    image_name: "dtb.img",
},

dtbo: {
    enabled: true,
    target: "dtbs",
    image_name: "dtbo.img",
    page_size: 4096,
},

Property	Description
enabled	Enable this type of device-tree output
qcom_merge	Use uwuAOSP's QCOM DT merge flow
src	Prebuilt DTB/DTBO input
target	Kbuild target; defaults to dtbs or dtbo.img
image_name	Output name; defaults to dtb.img or dtbo.img
config	Configuration file used by mkdtboimg cfg_create
input_globs	Glob used to collect DT files when Kbuild does not generate the final image directly
page_size	Page size for mkdtboimg create; defaults to 4096
custom_command	Command for cases the standard flow cannot handle

dtb.src and dtbo.src are only for prebuilt kernels. Source builds should collect device-tree outputs through a Kbuild target or input_globs. dtb.config and dtb.page_size are not currently supported.

custom_command can use $(kernelDir), $(kernelOut), and $(out). Use it only as a last resort; repeated flows should be implemented as a common capability.

When qcom_merge is enabled, both dtb.enabled and dtbo.enabled must be true. QCOM merge runs Kbuild using dtb.target, creates a separate merge working directory from the kernel DTS outputs, then generates DTB and DTBO. dtbo.target is not used in this mode.

Modules

modules: {
    enabled: true,
    build_targets: ["modules"],
    external_module_root: "kernel/vendor/device-modules",
    external_modules: [
        "vendor/example",
        "vendor/kbuild-module:kbuild",
    ],
    install_strip: true,
    auto_collect_deps: true,
    system_dlkm_module_install_list: ["modules.include.system_dlkm"],
    system_dlkm_module_load_list: ["modules.load.system_dlkm"],
    vendor_dlkm_module_install_list: ["modules.include.vendor_dlkm"],
    vendor_dlkm_module_load_list: ["modules.load.vendor_dlkm"],
    recovery_module_install_list: ["modules.include.recovery"],
    recovery_module_load_list: ["modules.load.recovery"],
},

Module install sets support system_dlkm, vendor_dlkm, vendor_ramdisk, and recovery. Each class must have both an install list and a load list; the load list must be a subset of the install list. Each class can also define a corresponding blocklist.

Normal external_modules entries are built using the external module's own Makefile, with the default target all; :all explicitly selects the same behavior. Entries with the :kbuild suffix use the main kernel Kbuild M= mode.

module_aliases uses the old_name.ko:new_name.ko format.

When auto_collect_deps is enabled, uwu_kernel collects dependencies of modules in the install list and adds them to the final install set. This requires lineage/scripts/collect-kernel-module-deps/collect-kernel-module-deps.py in the source tree.

vendor_dlkm_install_all adds all built modules not installed to system_dlkm to the vendor_dlkm install list.

A partition installer is created only when its install list or load list is configured. If one is configured, the other must also be configured. When system_dlkm is enabled, vendor_dlkm depends on the system_dlkm installer.

RBE wrapper

The RBE wrapper applies only to actual C and assembly source compilation. Other Clang calls, including preprocessing, -S, and dependency generation, still run locally.

rbe_wrapper should include the required rewrapper arguments. For example:

rbe_wrapper: "prebuilts/remoteexecution-client/live/rewrapper --labels=type=compile,lang=cpp,compiler=clang",