[PATCH v3 1/5] arm64: kasan: allow to init memory when setting tags

[Andrey Konovalov]

This change adds an argument to mte_set_mem_tag_range() that allows
to enable memory initialization when settinh the allocation tags.
The implementation uses stzg instruction instead of stg when this
argument indicates to initialize memory.

Combining setting allocation tags with memory initialization will
improve HW_TAGS KASAN performance when init_on_alloc/free is enabled.

This change doesn't integrate memory initialization with KASAN,
this is done is subsequent patches in this series.

Acked-by: Marco Elver <elver at google.com>
Signed-off-by: Andrey Konovalov <andreyknvl at google.com>
---
 arch/arm64/include/asm/memory.h    |  4 +--
 arch/arm64/include/asm/mte-kasan.h | 39 +++++++++++++++++++-----------
 mm/kasan/kasan.h                   |  9 ++++---
 3 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index c759faf7a1ff..f1ba48b4347d 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -248,8 +248,8 @@ static inline const void *__tag_set(const void *addr, u8 tag)
 #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))
+#define arch_set_mem_tag_range(addr, size, tag, init)	\
+			mte_set_mem_tag_range((addr), (size), (tag), (init))
 #endif /* CONFIG_KASAN_HW_TAGS */
 
 /*
diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h
index 7ab500e2ad17..570af3e99296 100644
--- a/arch/arm64/include/asm/mte-kasan.h
+++ b/arch/arm64/include/asm/mte-kasan.h
@@ -53,7 +53,8 @@ static inline u8 mte_get_random_tag(void)
  * Note: The address must be non-NULL and MTE_GRANULE_SIZE aligned and
  * size must be non-zero and MTE_GRANULE_SIZE aligned.
  */
-static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
+static inline void mte_set_mem_tag_range(void *addr, size_t size,
+						u8 tag, bool init)
 {
 	u64 curr, end;
 
@@ -63,18 +64,27 @@ static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
 	curr = (u64)__tag_set(addr, tag);
 	end = curr + size;
 
-	do {
-		/*
-		 * 'asm volatile' is required to prevent the compiler to move
-		 * the statement outside of the loop.
-		 */
-		asm volatile(__MTE_PREAMBLE "stg %0, [%0]"
-			     :
-			     : "r" (curr)
-			     : "memory");
-
-		curr += MTE_GRANULE_SIZE;
-	} while (curr != end);
+	/*
+	 * 'asm volatile' is required to prevent the compiler to move
+	 * the statement outside of the loop.
+	 */
+	if (init) {
+		do {
+			asm volatile(__MTE_PREAMBLE "stzg %0, [%0]"
+				     :
+				     : "r" (curr)
+				     : "memory");
+			curr += MTE_GRANULE_SIZE;
+		} while (curr != end);
+	} else {
+		do {
+			asm volatile(__MTE_PREAMBLE "stg %0, [%0]"
+				     :
+				     : "r" (curr)
+				     : "memory");
+			curr += MTE_GRANULE_SIZE;
+		} while (curr != end);
+	}
 }
 
 void mte_enable_kernel(void);
@@ -100,7 +110,8 @@ static inline u8 mte_get_random_tag(void)
 	return 0xFF;
 }
 
-static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
+static inline void mte_set_mem_tag_range(void *addr, size_t size,
+						u8 tag, bool init)
 {
 }
 
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 8c55634d6edd..7fbb32234414 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -291,7 +291,7 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 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))
+#define arch_set_mem_tag_range(addr, size, tag, init) ((void *)(addr))
 #endif
 
 #define hw_enable_tagging()			arch_enable_tagging()
@@ -299,7 +299,8 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 #define hw_set_tagging_report_once(state)	arch_set_tagging_report_once(state)
 #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))
+#define hw_set_mem_tag_range(addr, size, tag, init) \
+			arch_set_mem_tag_range((addr), (size), (tag), (init))
 
 #else /* CONFIG_KASAN_HW_TAGS */
 
@@ -343,7 +344,7 @@ static inline void kasan_poison(const void *addr, size_t size, u8 value)
 	if (WARN_ON(size & KASAN_GRANULE_MASK))
 		return;
 
-	hw_set_mem_tag_range((void *)addr, size, value);
+	hw_set_mem_tag_range((void *)addr, size, value, false);
 }
 
 static inline void kasan_unpoison(const void *addr, size_t size)
@@ -360,7 +361,7 @@ static inline void kasan_unpoison(const void *addr, size_t size)
 		return;
 	size = round_up(size, KASAN_GRANULE_SIZE);
 
-	hw_set_mem_tag_range((void *)addr, size, tag);
+	hw_set_mem_tag_range((void *)addr, size, tag, false);
 }
 
 static inline bool kasan_byte_accessible(const void *addr)
-- 
2.30.1.766.gb4fecdf3b7-goog