kasan: Add KASAN mode kernel parameter

Architectures supported by KASAN_HW_TAGS can provide a sync or async mode
of execution. On an MTE enabled arm64 hw for example this can be identified
with the synchronous or asynchronous tagging mode of execution.
In synchronous mode, an exception is triggered if a tag check fault occurs.
In asynchronous mode, if a tag check fault occurs, the TFSR_EL1 register is
updated asynchronously. The kernel checks the corresponding bits
periodically.

KASAN requires a specific kernel command line parameter to make use of this
hw features.

Add KASAN HW execution mode kernel command line parameter.

Note: This patch adds the kasan.mode kernel parameter and the
sync/async kernel command line options to enable the described features.

[ Add a new var instead of exposing kasan_arg_mode to be consistent with
  flags for other command line arguments. ]

Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://lore.kernel.org/r/20210315132019.33202-3-vincenzo.frascino@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 8c55634d6edd..a3d0d165d97d 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -21,6 +21,7 @@ static inline bool kasan_stack_collection_enabled(void)
 #endif
 
 extern bool kasan_flag_panic __ro_after_init;
+extern bool kasan_flag_async __ro_after_init;
 
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 #define KASAN_GRANULE_SIZE	(1UL << KASAN_SHADOW_SCALE_SHIFT)
@@ -275,8 +276,11 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 
 #ifdef CONFIG_KASAN_HW_TAGS
 
-#ifndef arch_enable_tagging
-#define arch_enable_tagging()
+#ifndef arch_enable_tagging_sync
+#define arch_enable_tagging_sync()
+#endif
+#ifndef arch_enable_tagging_async
+#define arch_enable_tagging_async()
 #endif
 #ifndef arch_init_tags
 #define arch_init_tags(max_tag)
@@ -294,7 +298,8 @@ 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 hw_enable_tagging()			arch_enable_tagging()
+#define hw_enable_tagging_sync()		arch_enable_tagging_sync()
+#define hw_enable_tagging_async()		arch_enable_tagging_async()
 #define hw_init_tags(max_tag)			arch_init_tags(max_tag)
 #define hw_set_tagging_report_once(state)	arch_set_tagging_report_once(state)
 #define hw_get_random_tag()			arch_get_random_tag()
@@ -303,7 +308,8 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 
 #else /* CONFIG_KASAN_HW_TAGS */
 
-#define hw_enable_tagging()
+#define hw_enable_tagging_sync()
+#define hw_enable_tagging_async()
 #define hw_set_tagging_report_once(state)
 
 #endif /* CONFIG_KASAN_HW_TAGS */
@@ -311,12 +317,12 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 #if defined(CONFIG_KASAN_HW_TAGS) && IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
 
 void kasan_set_tagging_report_once(bool state);
-void kasan_enable_tagging(void);
+void kasan_enable_tagging_sync(void);
 
 #else /* CONFIG_KASAN_HW_TAGS || CONFIG_KASAN_KUNIT_TEST */
 
 static inline void kasan_set_tagging_report_once(bool state) { }
-static inline void kasan_enable_tagging(void) { }
+static inline void kasan_enable_tagging_sync(void) { }
 
 #endif /* CONFIG_KASAN_HW_TAGS || CONFIG_KASAN_KUNIT_TEST */