arm64: kasan: add arch layer for memory tagging helpers

This patch add a set of arch_*() memory tagging helpers currently only
defined for arm64 when hardware tag-based KASAN is enabled.  These helpers
will be used by KASAN runtime to implement the hardware tag-based mode.

The arch-level indirection level is introduced to simplify adding hardware
tag-based KASAN support for other architectures in the future by defining
the appropriate arch_*() macros.

Link: https://lkml.kernel.org/r/fc9e5bb71201c03131a2fc00a74125723568dda9.1606161801.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm64/include/asm/memory.h

@@ -230,6 +230,15 @@ static inline const void *__tag_set(const void *addr, u8 tag)
 	return (const void *)(__addr | __tag_shifted(tag));
 }
 
+#ifdef CONFIG_KASAN_HW_TAGS
+#define arch_enable_tagging()			mte_enable_kernel()
+#define arch_init_tags(max_tag)			mte_init_tags(max_tag)
+#define arch_get_random_tag()			mte_get_random_tag()
+#define arch_get_mem_tag(addr)			mte_get_mem_tag(addr)
+#define arch_set_mem_tag_range(addr, size, tag)	\
+			mte_set_mem_tag_range((addr), (size), (tag))
+#endif /* CONFIG_KASAN_HW_TAGS */
+
 /*
  * Physical vs virtual RAM address space conversion.  These are
  * private definitions which should NOT be used outside memory.h

mm/kasan/kasan.h

@@ -243,6 +243,32 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 #define reset_tag(addr)		((void *)arch_kasan_reset_tag(addr))
 #define get_tag(addr)		arch_kasan_get_tag(addr)
 
+#ifdef CONFIG_KASAN_HW_TAGS
+
+#ifndef arch_enable_tagging
+#define arch_enable_tagging()
+#endif
+#ifndef arch_init_tags
+#define arch_init_tags(max_tag)
+#endif
+#ifndef arch_get_random_tag
+#define arch_get_random_tag()	(0xFF)
+#endif
+#ifndef arch_get_mem_tag
+#define arch_get_mem_tag(addr)	(0xFF)
+#endif
+#ifndef arch_set_mem_tag_range
+#define arch_set_mem_tag_range(addr, size, tag) ((void *)(addr))
+#endif
+
+#define hw_enable_tagging()			arch_enable_tagging()
+#define hw_init_tags(max_tag)			arch_init_tags(max_tag)
+#define hw_get_random_tag()			arch_get_random_tag()
+#define hw_get_mem_tag(addr)			arch_get_mem_tag(addr)
+#define hw_set_mem_tag_range(addr, size, tag)	arch_set_mem_tag_range((addr), (size), (tag))
+
+#endif /* CONFIG_KASAN_HW_TAGS */
+
 /*
  * Exported functions for interfaces called from assembly or from generated
  * code. Declarations here to avoid warning about missing declarations.