asan: Add --param=asan-kernel-mem-intrinsic-prefix= [PR108777]

While in the -fsanitize=address case libasan overloads memcpy, memset,
memmove and many other builtins, such that they are always instrumented,
Linux kernel for -fsanitize=kernel-address recently changed or is changing,
such that memcpy, memset and memmove actually aren't instrumented because
they are often used also from no_sanitize ("kernel-address") functions
and wants __{,hw,}asaN_{memcpy,memset,memmove} to be used instead
for the instrumented calls.  See e.g. the https://lkml.org/lkml/2023/2/9/1182
thread.  Without appropriate support on the compiler side, that will mean
any time a kernel-address instrumented function (most of them) calls
memcpy/memset/memmove, they will not be instrumented and thus won't catch
kernel bugs.  Apparently clang 15 has a param for this.

The following patch implements the same (except it is a usual GCC --param,
not -mllvm argument) on the GCC side.  I know this isn't a regression
bugfix, but given that -fsanitize=kernel-address has a single project that
uses it which badly wants this I think it would be worthwhile to make an
exception and get this into GCC 13 rather than waiting another year, it
won't affect non-kernel code, nor even the kernel unless the new parameter
is used.

2023-02-14  Jakub Jelinek  <jakub@redhat.com>

	PR sanitizer/108777
	* params.opt (-param=asan-kernel-mem-intrinsic-prefix=): New param.
	* asan.h (asan_memfn_rtl): Declare.
	* asan.cc (asan_memfn_rtls): New variable.
	(asan_memfn_rtl): New function.
	* builtins.cc (expand_builtin): If
	param_asan_kernel_mem_intrinsic_prefix and function is
	kernel-{,hw}address sanitized, emit calls to
	__{,hw}asan_{memcpy,memmove,memset} rather than
	{memcpy,memmove,memset}.  Use sanitize_flags_p (SANITIZE_ADDRESS)
	instead of flag_sanitize & SANITIZE_ADDRESS to check if
	asan_intercepted_p functions shouldn't be expanded inline.

	* gcc.dg/asan/pr108777-1.c: New test.
	* gcc.dg/asan/pr108777-2.c: New test.
	* gcc.dg/asan/pr108777-3.c: New test.
	* gcc.dg/asan/pr108777-4.c: New test.
	* gcc.dg/asan/pr108777-5.c: New test.
	* gcc.dg/asan/pr108777-6.c: New test.
	* gcc.dg/completion-3.c: Adjust expected multiline output.