I am not sure if this has been reported before (I did not see anything in the issue tracker) but I see the following error when building for ARCH=arm with CONFIG_RUST=y and CONFIG_KASAN=y (such as with allmodconfig)

$ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- mrproper allmodconfig prepare
error: kernel-address sanitizer is not supported for this target
error: aborting due to 1 previous error
make[4]: *** [rust/Makefile:654: rust/core.o] Error 1
...

Maybe something like this is needed for now, since I assume the fix for this will be in rustc?

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 71fc5dd4123f..73e6647bea46 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -136,7 +136,7 @@ config ARM
        select MMU_GATHER_RCU_TABLE_FREE if SMP && ARM_LPAE
        select HAVE_REGS_AND_STACK_ACCESS_API
        select HAVE_RSEQ
-       select HAVE_RUST if CPU_LITTLE_ENDIAN && CPU_32v7
+       select HAVE_RUST if CPU_LITTLE_ENDIAN && CPU_32v7 && !KASAN
        select HAVE_STACKPROTECTOR
        select HAVE_SYSCALL_TRACEPOINTS
        select HAVE_UID16