KernelMemorySanitizer (KMSAN) is a dynamic detector of uses of
uninitialized values in the kernel. It is based on compiler
instrumentation provided by Clang and thus requires Clang to build.

An important note is that KMSAN is not intended for production use,
because it drastically increases kernel memory footprint and slows
the whole system down.

See Documentation/dev-tools/kmsan.rst for more details.

source code:

arch/x86/mm/kmsan_shadow.c