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Date:   Wed, 14 Oct 2020 22:44:35 +0200
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Subject: [PATCH RFC 7/8] arm64: kasan: Add system_supports_tags helper
From:   Andrey Konovalov <andreyknvl@google.com>
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>
Cc:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Elena Petrova <lenaptr@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
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Precedence: bulk

Add a helper that exposes information about whether the system supports
memory tagging to be called in generic code.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://linux-review.googlesource.com/id/Ib4b56a42c57c6293df29a0cdfee334c3ca7bdab4
---
 arch/arm64/include/asm/memory.h | 1 +
 mm/kasan/kasan.h                | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index b5d6b824c21c..6d2b7c54780e 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -232,6 +232,7 @@ static inline const void *__tag_set(const void *addr, u8 tag)
 }
 
 #ifdef CONFIG_KASAN_HW_TAGS
+#define arch_system_supports_tags()		system_supports_mte()
 #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)
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index e5b8367a07f2..47d6074c7958 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -257,6 +257,9 @@ 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)
 
+#ifndef arch_system_supports_tags
+#define arch_system_supports_tags() (false)
+#endif
 #ifndef arch_init_tags
 #define arch_init_tags(max_tag)
 #endif
@@ -270,6 +273,7 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 #define arch_set_mem_tag_range(addr, size, tag) ((void *)(addr))
 #endif
 
+#define system_supports_tags()			arch_system_supports_tags()
 #define init_tags(max_tag)			arch_init_tags(max_tag)
 #define get_random_tag()			arch_get_random_tag()
 #define get_mem_tag(addr)			arch_get_mem_tag(addr)
-- 
2.28.0.1011.ga647a8990f-goog