#
# How to build the KMI ABI test kernel module, kmi_sym.ko
#

1. Set up the GKI source.
   # Set up and export GKI_DIR to be used for kernel module building
   $ cd $GKI_DIR
   $ repo init -u https://android.googlesource.com/kernel/manifest \
       -b common-android12-5.10
   $ repo sync
   See "GKI Monthly Branch Handbook" for details.
2. Build arm64 GKI under $GKI_DIR
   $ BUILD_CONFIG=common/build.config.gki.aarch64 build/build.sh -j16
3. Download a supported kernel symbol file, vmlinux.symvers, from GKI AB:
   $ export GKI_BID=7618735
   https://ci.android.com/builds/submitted/$GKI_BID/kernel_aarch64/latest
   $ cp vmlinux.symvers $ANDROID_BUILD_TOP/development/gki/kmi_abi_chk/vmlinux.symvers-$GKI_BID
4. Replace the Module.symvers just built with the supported kernel symbol file.
   $ cp vmlinux.symvers $GKI_DIR/out/android12-5.10/common/Module.symvers
5. Create the KMI symbol list include file:
   $ cd development/gki/kmi_abi_chk
   $ cp $GKI_DIR/out/android12-5.10/common/Module.symvers vmlinux.symvers-$GKI_BID
   $ awk '{printf("\t.xword\t%s\n",$2)}' vmlinux.symvers-$GKI_BID >> kmi_sym_list-$GKI_BID.inc
   Note that kmi_sym_list-7618735.inc included in the current directory is a
   version modified from the one based on vmlinux.symvers of build 7618735, the
   initial GKI 5.10 released in July, 2021. Search b/197035344 for details.
6. Build the kernel module
   $ make ARCH=arm64 CROSS_COMPILE=aarch64 LLVM=1 LLVM_IAS=1 LTO=thin

A few prebuilt test kernel modules, kmi_sym-*.ko, for arm64 GKI 5.10
2021-07 and later builds is included under prebuilts/ directory.

#
# How to use/run KMI test kernel module, kmi_sym.ko, on GKI
#

1. Copy the test kernel module to the Android device
   $ adb push kmi_sym.ko /data/local/tmp
2. "Root" the Android device we'd like to run the test
   $ adb root
3. Check the kernel information on the device
   emulator64_arm64:/ # uname -a
   Linux localhost 5.10.43-android12-9-00005-g376ecc372342-ab7614753 #1 SMP PREEMPT Thu Aug 5 15:12:49 UTC 2021 aarch64
4. Load the test kernel module
   emulator64_arm64:/ # lsmod | grep kmi_sym
   emulator64_arm64:/ # insmod /data/local/tmp/kmi_sym.ko; echo $?
   0
5. Verify the test kernel module is loaded successfully
   emulator64_arm64:/ # lsmod | grep kmi_sym
   kmi_sym                57344  0
   emulator64_arm64:/ # dmesg | grep KMI
   [ 1669.833480] 5317 KMI ABI symbols at 00000000d34c59ea
6. Unload the test kernel module
   emulator64_arm64:/ # rmmod kmi_sym; echo $?
   0
   emulator64_arm64:/ # dmesg | grep KMI
   [ 1669.833480] 5317 KMI ABI symbols at 00000000d34c59ea
   [ 1860.571944] Cleaning up KMI ABI.