kasan: move and hide kasan_save_enable/restore_multi_shot

 - Move kasan_save_enable/restore_multi_shot() declarations to
   mm/kasan/kasan.h, as there is no need for them to be visible outside
   of KASAN implementation.

 - Only define and export these functions when KASAN tests are enabled.

 - Move their definitions closer to other test-related code in report.c.

Link: https://lkml.kernel.org/r/6ba637333b78447f027d775f2d55ab1a40f63c99.1646237226.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: xairy

include/linux/kasan.h

@@ -267,10 +267,6 @@ static __always_inline bool kasan_check_byte(const void *addr)
 	return true;
 }
 
-
-bool kasan_save_enable_multi_shot(void);
-void kasan_restore_multi_shot(bool enabled);
-
 #else /* CONFIG_KASAN */
 
 static inline slab_flags_t kasan_never_merge(void)

mm/kasan/kasan.h

@@ -492,6 +492,13 @@ static inline bool kasan_arch_is_ready(void)	{ return true; }
 #error kasan_arch_is_ready only works in KASAN generic outline mode!
 #endif
 
+#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
+
+bool kasan_save_enable_multi_shot(void);
+void kasan_restore_multi_shot(bool enabled);
+
+#endif
+
 /*
  * Exported functions for interfaces called from assembly or from generated
  * code. Declarations here to avoid warning about missing declarations.

mm/kasan/report.c

@@ -64,19 +64,6 @@ static int __init early_kasan_fault(char *arg)
 }
 early_param("kasan.fault", early_kasan_fault);
 
-bool kasan_save_enable_multi_shot(void)
-{
-	return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
-}
-EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
-
-void kasan_restore_multi_shot(bool enabled)
-{
-	if (!enabled)
-		clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
-}
-EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
-
 static int __init kasan_set_multi_shot(char *str)
 {
 	set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
@@ -109,6 +96,23 @@ static bool report_enabled(void)
 	return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 }
 
+#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
+
+bool kasan_save_enable_multi_shot(void)
+{
+	return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
+}
+EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
+
+void kasan_restore_multi_shot(bool enabled)
+{
+	if (!enabled)
+		clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
+}
+EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
+
+#endif
+
 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
 static void update_kunit_status(bool sync)
 {