Compiling AOSP Kernel with KASAN

I'm struggling to compile the Linux kernel for usage in AOSP with KASAN & KCOV enabled. I then intend to flash it to a Pixel 2 XL (taimen) and use syzkaller to fuzz it.

This is what I did:

1. Build unmodified kernel (works)

My reference: https://source.android.com/setup/build/building-kernels

• Determine branch... android-msm-wahoo-4.4-pie-qpr2
• $ repo init -u https://android.googlesource.com/kernel/manifest -b android-msm-wahoo-4.4-pie-qpr2
• $ repo sync -j8 -c
• $ build/build.sh -j8
• Connect phone via USB
• $ adb reboot bootloader
• $ fastboot boot out/android-msm-wahoo-4.4/dist/Image.lz4-dtb (Works fine)

2. Build kernel with KASAN & KCOV (fails)

• To change kernel config symbols, edit POST_DEFCONFIG_CMDS in build/build.config
  • Copy from https://source.android.com/setup/build/building-kernels#customize-config
  • Modify as needed, use -d to disable, -e to enable a config option
  • Result:

POST_DEFCONFIG_CMDS="check_defconfig && update_debug_config"
function update_debug_config() {
    ${KERNEL_DIR}/scripts/config --file ${OUT_DIR}/.config \
         -d CONFIG_KERNEL_LZ4 \
         -e CONFIG_KASAN \
         -e CONFIG_KASAN_INLINE \
         -e CONFIG_KCOV \
         -e CONFIG_SLUB \
         -e CONFIG_SLUB_DEBUG \
         --set-val FRAME_WARN 0
    (cd ${OUT_DIR} && \
     make O=${OUT_DIR} $archsubarch CC=${CC} CROSS_COMPILE=${CROSS_COMPILE} olddefconfig)
}

• $ build/build.sh -j8

But after CHK include/generated/compile.h I get many undefined reference errors to various asan-symbols, e.g. undefined reference to __asan_alloca_poison.

I did some research and read about adding -fsantitize=address and -shared-libasan (or -shared-libsan) to CFLAGS AND LDFLAGS. I did that (for which I had to hard-code it into build/build.sh, isn't there a more convenient way?), but to no avail:

I ended up with aarch64-linux-android-ld: -f may not be used without -shared.

So I tried reading up on ld's -shared flag and adding it to LDFLAGS (more like a guess really). Resulted in aarch64-linux-android-ld: -r and -shared may not be used together.

Really don't know where to go from here and what's going wrong in general?

Any help really appreciated!

Update: Using gcc instead of clang seemed to resolve the issue, but caused the touchscreen on the phone to be unusable (not responding). I am looking into the reasons...