[PATCH v4 1/5] mm/kasan: Introduce __kasan_check_{read,write}

[Marco Elver <elver@google.com>]

This introduces __kasan_check_{read,write}. __kasan_check functions may
be used from anywhere, even compilation units that disable
instrumentation selectively.

This change eliminates the need for the __KASAN_INTERNAL definition.

Signed-off-by: Marco Elver <elver@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: kasan-dev@googlegroups.com
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
---
v3:
* Fix Formatting and split introduction of __kasan_check_* and returning
  bool into 2 patches.
---
 include/linux/kasan-checks.h | 31 ++++++++++++++++++++++++++++---
 mm/kasan/common.c            | 10 ++++------
 2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/include/linux/kasan-checks.h b/include/linux/kasan-checks.h
index a61dc075e2ce..19a0175d2452 100644
--- a/include/linux/kasan-checks.h
+++ b/include/linux/kasan-checks.h
@@ -2,9 +2,34 @@
 #ifndef _LINUX_KASAN_CHECKS_H
 #define _LINUX_KASAN_CHECKS_H
 
-#if defined(__SANITIZE_ADDRESS__) || defined(__KASAN_INTERNAL)
-void kasan_check_read(const volatile void *p, unsigned int size);
-void kasan_check_write(const volatile void *p, unsigned int size);
+/*
+ * __kasan_check_*: Always available when KASAN is enabled. This may be used
+ * even in compilation units that selectively disable KASAN, but must use KASAN
+ * to validate access to an address.   Never use these in header files!
+ */
+#ifdef CONFIG_KASAN
+void __kasan_check_read(const volatile void *p, unsigned int size);
+void __kasan_check_write(const volatile void *p, unsigned int size);
+#else
+static inline void __kasan_check_read(const volatile void *p, unsigned int size)
+{ }
+static inline void __kasan_check_write(const volatile void *p, unsigned int size)
+{ }
+#endif
+
+/*
+ * kasan_check_*: Only available when the particular compilation unit has KASAN
+ * instrumentation enabled. May be used in header files.
+ */
+#ifdef __SANITIZE_ADDRESS__
+static inline void kasan_check_read(const volatile void *p, unsigned int size)
+{
+	__kasan_check_read(p, size);
+}
+static inline void kasan_check_write(const volatile void *p, unsigned int size)
+{
+	__kasan_check_read(p, size);
+}
 #else
 static inline void kasan_check_read(const volatile void *p, unsigned int size)
 { }
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 242fdc01aaa9..6bada42cc152 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -14,8 +14,6 @@
  *
  */
 
-#define __KASAN_INTERNAL
-
 #include <linux/export.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
@@ -89,17 +87,17 @@ void kasan_disable_current(void)
 	current->kasan_depth--;
 }
 
-void kasan_check_read(const volatile void *p, unsigned int size)
+void __kasan_check_read(const volatile void *p, unsigned int size)
 {
 	check_memory_region((unsigned long)p, size, false, _RET_IP_);
 }
-EXPORT_SYMBOL(kasan_check_read);
+EXPORT_SYMBOL(__kasan_check_read);
 
-void kasan_check_write(const volatile void *p, unsigned int size)
+void __kasan_check_write(const volatile void *p, unsigned int size)
 {
 	check_memory_region((unsigned long)p, size, true, _RET_IP_);
 }
-EXPORT_SYMBOL(kasan_check_write);
+EXPORT_SYMBOL(__kasan_check_write);
 
 #undef memset
 void *memset(void *addr, int c, size_t len)
-- 
2.22.0.410.gd8fdbe21b5-goog