MIPS: Enable Undefined Behavior Sanitizer UBSAN

Select ARCH_HAS_UBSAN_SANITIZE_ALL in order to allow the user to
enable CONFIG_UBSAN_SANITIZE_ALL and instrument the entire kernel for
ubsan checks.
We exclude the VDSO from this because its build doesn't include the
__ubsan_handle_*() functions that the kernel proper defines in from
lib/ubsan.c, and the VDSO would have no sane way to report errors even
if it had definitions of these functions.

Signed-off-by: Hassan Naveed <hnaveed@wavecomp.com>
Reviewed-by: Paul Burton <paul.burton@mips.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/21179/
Cc: <linux-mips@linux-mips.org>

arch/mips/Kconfig

@@ -7,6 +7,7 @@ config MIPS
 	select ARCH_DISCARD_MEMBLOCK
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
+	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_SUPPORTS_UPROBES
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF if 64BIT

arch/mips/vdso/Makefile

@@ -50,6 +50,7 @@ VDSO_LDFLAGS := \
 	$(call cc-ldoption, -Wl$(comma)--build-id)
 
 GCOV_PROFILE := n
+UBSAN_SANITIZE := n
 
 #
 # Shared build commands.