kasan, arm64: tests supports for HW_TAGS async mode

This change adds KASAN-KUnit tests support for the async HW_TAGS mode.

In async mode, tag fault aren't being generated synchronously when a
bad access happens, but are instead explicitly checked for by the kernel.

As each KASAN-KUnit test expect a fault to happen before the test is over,
check for faults as a part of the test handler.

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: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20210315132019.33202-10-vincenzo.frascino@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/memory.h

@@ -246,6 +246,7 @@ static inline const void *__tag_set(const void *addr, u8 tag)
 #define arch_enable_tagging_sync()		mte_enable_kernel_sync()
 #define arch_enable_tagging_async()		mte_enable_kernel_async()
 #define arch_set_tagging_report_once(state)	mte_set_report_once(state)
+#define arch_force_async_tag_fault()		mte_check_tfsr_exit()
 #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)

lib/test_kasan.c

@@ -69,10 +69,10 @@ static void kasan_test_exit(struct kunit *test)
  * resource named "kasan_data". Do not use this name for KUnit resources
  * outside of KASAN tests.
  *
- * For hardware tag-based KASAN, when a tag fault happens, tag checking is
- * normally auto-disabled. When this happens, this test handler reenables
- * tag checking. As tag checking can be only disabled or enabled per CPU, this
- * handler disables migration (preemption).
+ * For hardware tag-based KASAN in sync mode, when a tag fault happens, tag
+ * checking is auto-disabled. When this happens, this test handler reenables
+ * tag checking. As tag checking can be only disabled or enabled per CPU,
+ * this handler disables migration (preemption).
  *
  * Since the compiler doesn't see that the expression can change the fail_data
  * fields, it can reorder or optimize away the accesses to those fields.
@@ -80,7 +80,8 @@ static void kasan_test_exit(struct kunit *test)
  * expression to prevent that.
  */
 #define KUNIT_EXPECT_KASAN_FAIL(test, expression) do {		\
-	if (IS_ENABLED(CONFIG_KASAN_HW_TAGS))			\
+	if (IS_ENABLED(CONFIG_KASAN_HW_TAGS) &&			\
+	    !kasan_async_mode_enabled())			\
 		migrate_disable();				\
 	WRITE_ONCE(fail_data.report_expected, true);		\
 	WRITE_ONCE(fail_data.report_found, false);		\
@@ -92,10 +93,14 @@ static void kasan_test_exit(struct kunit *test)
 	barrier();						\
 	expression;						\
 	barrier();						\
+	if (kasan_async_mode_enabled())				\
+		kasan_force_async_fault();			\
+	barrier();						\
 	KUNIT_EXPECT_EQ(test,					\
 			READ_ONCE(fail_data.report_expected),	\
 			READ_ONCE(fail_data.report_found));	\
-	if (IS_ENABLED(CONFIG_KASAN_HW_TAGS)) {			\
+	if (IS_ENABLED(CONFIG_KASAN_HW_TAGS) &&			\
+	    !kasan_async_mode_enabled()) {			\
 		if (READ_ONCE(fail_data.report_found))		\
 			kasan_enable_tagging_sync();		\
 		migrate_enable();				\

mm/kasan/hw_tags.c

@@ -252,4 +252,10 @@ void kasan_enable_tagging_sync(void)
 }
 EXPORT_SYMBOL_GPL(kasan_enable_tagging_sync);
 
+void kasan_force_async_fault(void)
+{
+	hw_force_async_tag_fault();
+}
+EXPORT_SYMBOL_GPL(kasan_force_async_fault);
+
 #endif

mm/kasan/kasan.h

@@ -304,6 +304,9 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 #ifndef arch_set_tagging_report_once
 #define arch_set_tagging_report_once(state)
 #endif
+#ifndef arch_force_async_tag_fault
+#define arch_force_async_tag_fault()
+#endif
 #ifndef arch_get_random_tag
 #define arch_get_random_tag()	(0xFF)
 #endif
@@ -318,6 +321,7 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 #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_force_async_tag_fault()		arch_force_async_tag_fault()
 #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))
@@ -334,11 +338,13 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
 
 void kasan_set_tagging_report_once(bool state);
 void kasan_enable_tagging_sync(void);
+void kasan_force_async_fault(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_sync(void) { }
+static inline void kasan_force_async_fault(void) { }
 
 #endif /* CONFIG_KASAN_HW_TAGS || CONFIG_KASAN_KUNIT_TEST */
 

mm/kasan/report.c

@@ -366,6 +366,11 @@ void kasan_report_async(void)
 {
 	unsigned long flags;
 
+#if IS_ENABLED(CONFIG_KUNIT)
+	if (current->kunit_test)
+		kasan_update_kunit_status(current->kunit_test);
+#endif /* IS_ENABLED(CONFIG_KUNIT) */
+
 	start_report(&flags);
 	pr_err("BUG: KASAN: invalid-access\n");
 	pr_err("Asynchronous mode enabled: no access details available\n");