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Compiling the Kernel

Local Build · Step 3

This example uses the Xiaomi Mix2s kernel for the custom ROM Evolution X 10:

• Source: https://github.com/Evolution-X-Devices/kernel_xiaomi_sdm845
• Branch: vic

Toolchain: AOSP Clang 12 + Google GCC 4.9. Assumed directory layout:

/home/username/
├── Clang/clang_aosp_12/bin/
├── Gcc/
│   ├── google_gcc_arm/bin/
│   └── google_gcc_arm64/bin/
└── Kernel/evox_mix2s_a15/

Step 1: Find the defconfig File

The defconfig file lives under arch/arm64/configs/ in the kernel source. Common naming patterns:

• <device_codename>_defconfig
• <kernel_name>_defconfig
• The most recently modified defconfig file in that directory

This example: two config files need to be merged:

• vendor/mi845_defconfig — base Xiaomi config
• vendor/polaris.config — Mix2s-specific driver config

Step 2: Generate the .config File

export PATH=/home/username/Clang/clang_aosp_12/bin:$PATH

make ARCH=arm64 O=out CC="clang" \
  CROSS_COMPILE="/home/username/Gcc/google_gcc_arm64/bin/aarch64-linux-android-" \
  CROSS_COMPILE_ARM32="/home/username/Gcc/google_gcc_arm/bin/arm-linux-androideabi-" \
  CLANG_TRIPLE=aarch64-linux-gnu- LD=ld.lld \
  vendor/mi845_defconfig vendor/polaris.config

Flag	Description
ARCH=arm64	Target architecture
O=out	Output directory, keeps build artifacts separate from source
CROSS_COMPILE	Cross-compiler path (GCC ARM64)
CROSS_COMPILE_ARM32	Cross-compiler path (GCC ARM)
CLANG_TRIPLE	Fallback Clang target triple, used if the primary Clang fails
LD=ld.lld	Use Clang's built-in linker instead of the system default

On success, out/.config will be generated.

Step 3: Start the Build

make -j$(nproc --all) ARCH=arm64 O=out CC="clang" \
  CROSS_COMPILE="/home/username/Gcc/google_gcc_arm64/bin/aarch64-linux-android-" \
  CROSS_COMPILE_ARM32="/home/username/Gcc/google_gcc_arm/bin/arm-linux-androideabi-" \
  CLANG_TRIPLE=aarch64-linux-gnu- LD=ld.lld \
  vendor/mi845_defconfig vendor/polaris.config 2>&1 | tee error.log

Flag	Description
-j$(nproc --all)	Use all available CPU cores; or specify e.g. -j4
2>&1 | tee error.log	Save build output to error.log for debugging

Build time is roughly 5–30 minutes (1+ hour on a 2-core machine). A successful build ends with a line like:

OBJCOPY arch/arm64/boot/Image.gz

If there is no Error 2 in the output and the OBJCOPY line is present, the build succeeded. The kernel image is at out/arch/arm64/boot/.