Merge tag 'kcsan.2021.11.11a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull KCSAN updates from Paul McKenney:
 "This contains initialization fixups, testing improvements, addition of
  instruction pointer to data-race reports, and scoped data-race checks"

* tag 'kcsan.2021.11.11a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  kcsan: selftest: Cleanup and add missing __init
  kcsan: Move ctx to start of argument list
  kcsan: Support reporting scoped read-write access type
  kcsan: Start stack trace with explicit location if provided
  kcsan: Save instruction pointer for scoped accesses
  kcsan: Add ability to pass instruction pointer of access to reporting
  kcsan: test: Fix flaky test case
  kcsan: test: Use kunit_skip() to skip tests
  kcsan: test: Defer kcsan_test_init() after kunit initialization

Author: torvalds

include/linux/kcsan-checks.h

@@ -100,9 +100,12 @@ void kcsan_set_access_mask(unsigned long mask);
 /* Scoped access information. */
 struct kcsan_scoped_access {
 	struct list_head list;
+	/* Access information. */
 	const volatile void *ptr;
 	size_t size;
 	int type;
+	/* Location where scoped access was set up. */
+	unsigned long ip;
 };
 /*
  * Automatically call kcsan_end_scoped_access() when kcsan_scoped_access goes

kernel/kcsan/core.c

@@ -202,6 +202,9 @@ static __always_inline struct kcsan_ctx *get_ctx(void)
 	return in_task() ? &current->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
 }
 
+static __always_inline void
+check_access(const volatile void *ptr, size_t size, int type, unsigned long ip);
+
 /* Check scoped accesses; never inline because this is a slow-path! */
 static noinline void kcsan_check_scoped_accesses(void)
 {
@@ -210,14 +213,16 @@ static noinline void kcsan_check_scoped_accesses(void)
 	struct kcsan_scoped_access *scoped_access;
 
 	ctx->scoped_accesses.prev = NULL;  /* Avoid recursion. */
-	list_for_each_entry(scoped_access, &ctx->scoped_accesses, list)
-		__kcsan_check_access(scoped_access->ptr, scoped_access->size, scoped_access->type);
+	list_for_each_entry(scoped_access, &ctx->scoped_accesses, list) {
+		check_access(scoped_access->ptr, scoped_access->size,
+			     scoped_access->type, scoped_access->ip);
+	}
 	ctx->scoped_accesses.prev = prev_save;
 }
 
 /* Rules for generic atomic accesses. Called from fast-path. */
 static __always_inline bool
-is_atomic(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
+is_atomic(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size, int type)
 {
 	if (type & KCSAN_ACCESS_ATOMIC)
 		return true;
@@ -254,7 +259,7 @@ is_atomic(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx
 }
 
 static __always_inline bool
-should_watch(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
+should_watch(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size, int type)
 {
 	/*
 	 * Never set up watchpoints when memory operations are atomic.
@@ -263,7 +268,7 @@ should_watch(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *
 	 * should not count towards skipped instructions, and (2) to actually
 	 * decrement kcsan_atomic_next for consecutive instruction stream.
 	 */
-	if (is_atomic(ptr, size, type, ctx))
+	if (is_atomic(ctx, ptr, size, type))
 		return false;
 
 	if (this_cpu_dec_return(kcsan_skip) >= 0)
@@ -350,6 +355,7 @@ void kcsan_restore_irqtrace(struct task_struct *task)
 static noinline void kcsan_found_watchpoint(const volatile void *ptr,
 					    size_t size,
 					    int type,
+					    unsigned long ip,
 					    atomic_long_t *watchpoint,
 					    long encoded_watchpoint)
 {
@@ -396,7 +402,7 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
 
 	if (consumed) {
 		kcsan_save_irqtrace(current);
-		kcsan_report_set_info(ptr, size, type, watchpoint - watchpoints);
+		kcsan_report_set_info(ptr, size, type, ip, watchpoint - watchpoints);
 		kcsan_restore_irqtrace(current);
 	} else {
 		/*
@@ -416,7 +422,7 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
 }
 
 static noinline void
-kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
+kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned long ip)
 {
 	const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
 	const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
@@ -568,8 +574,8 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
 		if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE)
 			atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
 
-		kcsan_report_known_origin(ptr, size, type, value_change,
-					  watchpoint - watchpoints,
+		kcsan_report_known_origin(ptr, size, type, ip,
+					  value_change, watchpoint - watchpoints,
 					  old, new, access_mask);
 	} else if (value_change == KCSAN_VALUE_CHANGE_TRUE) {
 		/* Inferring a race, since the value should not have changed. */
@@ -578,8 +584,10 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
 		if (is_assert)
 			atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
 
-		if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert)
-			kcsan_report_unknown_origin(ptr, size, type, old, new, access_mask);
+		if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert) {
+			kcsan_report_unknown_origin(ptr, size, type, ip,
+						    old, new, access_mask);
+		}
 	}
 
 	/*
@@ -596,8 +604,8 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
 	user_access_restore(ua_flags);
 }
 
-static __always_inline void check_access(const volatile void *ptr, size_t size,
-					 int type)
+static __always_inline void
+check_access(const volatile void *ptr, size_t size, int type, unsigned long ip)
 {
 	const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
 	atomic_long_t *watchpoint;
@@ -625,13 +633,12 @@ static __always_inline void check_access(const volatile void *ptr, size_t size,
 	 */
 
 	if (unlikely(watchpoint != NULL))
-		kcsan_found_watchpoint(ptr, size, type, watchpoint,
-				       encoded_watchpoint);
+		kcsan_found_watchpoint(ptr, size, type, ip, watchpoint, encoded_watchpoint);
 	else {
 		struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */
 
-		if (unlikely(should_watch(ptr, size, type, ctx)))
-			kcsan_setup_watchpoint(ptr, size, type);
+		if (unlikely(should_watch(ctx, ptr, size, type)))
+			kcsan_setup_watchpoint(ptr, size, type, ip);
 		else if (unlikely(ctx->scoped_accesses.prev))
 			kcsan_check_scoped_accesses();
 	}
@@ -757,14 +764,15 @@ kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type,
 {
 	struct kcsan_ctx *ctx = get_ctx();
 
-	__kcsan_check_access(ptr, size, type);
+	check_access(ptr, size, type, _RET_IP_);
 
 	ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
 
 	INIT_LIST_HEAD(&sa->list);
 	sa->ptr = ptr;
 	sa->size = size;
 	sa->type = type;
+	sa->ip = _RET_IP_;
 
 	if (!ctx->scoped_accesses.prev) /* Lazy initialize list head. */
 		INIT_LIST_HEAD(&ctx->scoped_accesses);
@@ -796,13 +804,13 @@ void kcsan_end_scoped_access(struct kcsan_scoped_access *sa)
 
 	ctx->disable_count--;
 
-	__kcsan_check_access(sa->ptr, sa->size, sa->type);
+	check_access(sa->ptr, sa->size, sa->type, sa->ip);
 }
 EXPORT_SYMBOL(kcsan_end_scoped_access);
 
 void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
 {
-	check_access(ptr, size, type);
+	check_access(ptr, size, type, _RET_IP_);
 }
 EXPORT_SYMBOL(__kcsan_check_access);
 
@@ -823,7 +831,7 @@ EXPORT_SYMBOL(__kcsan_check_access);
 	void __tsan_read##size(void *ptr);                                     \
 	void __tsan_read##size(void *ptr)                                      \
 	{                                                                      \
-		check_access(ptr, size, 0);                                    \
+		check_access(ptr, size, 0, _RET_IP_);                          \
 	}                                                                      \
 	EXPORT_SYMBOL(__tsan_read##size);                                      \
 	void __tsan_unaligned_read##size(void *ptr)                            \
@@ -832,7 +840,7 @@ EXPORT_SYMBOL(__kcsan_check_access);
 	void __tsan_write##size(void *ptr);                                    \
 	void __tsan_write##size(void *ptr)                                     \
 	{                                                                      \
-		check_access(ptr, size, KCSAN_ACCESS_WRITE);                   \
+		check_access(ptr, size, KCSAN_ACCESS_WRITE, _RET_IP_);         \
 	}                                                                      \
 	EXPORT_SYMBOL(__tsan_write##size);                                     \
 	void __tsan_unaligned_write##size(void *ptr)                           \
@@ -842,7 +850,8 @@ EXPORT_SYMBOL(__kcsan_check_access);
 	void __tsan_read_write##size(void *ptr)                                \
 	{                                                                      \
 		check_access(ptr, size,                                        \
-			     KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE);      \
+			     KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE,       \
+			     _RET_IP_);                                        \
 	}                                                                      \
 	EXPORT_SYMBOL(__tsan_read_write##size);                                \
 	void __tsan_unaligned_read_write##size(void *ptr)                      \
@@ -858,14 +867,14 @@ DEFINE_TSAN_READ_WRITE(16);
 void __tsan_read_range(void *ptr, size_t size);
 void __tsan_read_range(void *ptr, size_t size)
 {
-	check_access(ptr, size, 0);
+	check_access(ptr, size, 0, _RET_IP_);
 }
 EXPORT_SYMBOL(__tsan_read_range);
 
 void __tsan_write_range(void *ptr, size_t size);
 void __tsan_write_range(void *ptr, size_t size)
 {
-	check_access(ptr, size, KCSAN_ACCESS_WRITE);
+	check_access(ptr, size, KCSAN_ACCESS_WRITE, _RET_IP_);
 }
 EXPORT_SYMBOL(__tsan_write_range);
 
@@ -886,7 +895,8 @@ EXPORT_SYMBOL(__tsan_write_range);
 				       IS_ALIGNED((unsigned long)ptr, size);   \
 		if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic)      \
 			return;                                                \
-		check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0);  \
+		check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0,   \
+			     _RET_IP_);                                        \
 	}                                                                      \
 	EXPORT_SYMBOL(__tsan_volatile_read##size);                             \
 	void __tsan_unaligned_volatile_read##size(void *ptr)                   \
@@ -901,7 +911,8 @@ EXPORT_SYMBOL(__tsan_write_range);
 			return;                                                \
 		check_access(ptr, size,                                        \
 			     KCSAN_ACCESS_WRITE |                              \
-				     (is_atomic ? KCSAN_ACCESS_ATOMIC : 0));   \
+				     (is_atomic ? KCSAN_ACCESS_ATOMIC : 0),    \
+			     _RET_IP_);                                        \
 	}                                                                      \
 	EXPORT_SYMBOL(__tsan_volatile_write##size);                            \
 	void __tsan_unaligned_volatile_write##size(void *ptr)                  \
@@ -955,7 +966,7 @@ EXPORT_SYMBOL(__tsan_init);
 	u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder)                       \
 	{                                                                                          \
 		if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
-			check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC);              \
+			check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC, _RET_IP_);    \
 		}                                                                                  \
 		return __atomic_load_n(ptr, memorder);                                             \
 	}                                                                                          \
@@ -965,7 +976,7 @@ EXPORT_SYMBOL(__tsan_init);
 	{                                                                                          \
 		if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 			check_access(ptr, bits / BITS_PER_BYTE,                                    \
-				     KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC);                    \
+				     KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC, _RET_IP_);          \
 		}                                                                                  \
 		__atomic_store_n(ptr, v, memorder);                                                \
 	}                                                                                          \
@@ -978,7 +989,7 @@ EXPORT_SYMBOL(__tsan_init);
 		if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 			check_access(ptr, bits / BITS_PER_BYTE,                                    \
 				     KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE |                  \
-					     KCSAN_ACCESS_ATOMIC);                                 \
+					     KCSAN_ACCESS_ATOMIC, _RET_IP_);                       \
 		}                                                                                  \
 		return __atomic_##op##suffix(ptr, v, memorder);                                    \
 	}                                                                                          \
@@ -1010,7 +1021,7 @@ EXPORT_SYMBOL(__tsan_init);
 		if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 			check_access(ptr, bits / BITS_PER_BYTE,                                    \
 				     KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE |                  \
-					     KCSAN_ACCESS_ATOMIC);                                 \
+					     KCSAN_ACCESS_ATOMIC, _RET_IP_);                       \
 		}                                                                                  \
 		return __atomic_compare_exchange_n(ptr, exp, val, weak, mo, fail_mo);              \
 	}                                                                                          \
@@ -1025,7 +1036,7 @@ EXPORT_SYMBOL(__tsan_init);
 		if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {                                    \
 			check_access(ptr, bits / BITS_PER_BYTE,                                    \
 				     KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE |                  \
-					     KCSAN_ACCESS_ATOMIC);                                 \
+					     KCSAN_ACCESS_ATOMIC, _RET_IP_);                       \
 		}                                                                                  \
 		__atomic_compare_exchange_n(ptr, &exp, val, 0, mo, fail_mo);                       \
 		return exp;                                                                        \

kernel/kcsan/kcsan.h

@@ -121,22 +121,22 @@ enum kcsan_value_change {
  * to be consumed by the reporting thread. No report is printed yet.
  */
 void kcsan_report_set_info(const volatile void *ptr, size_t size, int access_type,
-			   int watchpoint_idx);
+			   unsigned long ip, int watchpoint_idx);
 
 /*
  * The calling thread observed that the watchpoint it set up was hit and
  * consumed: print the full report based on information set by the racing
  * thread.
  */
 void kcsan_report_known_origin(const volatile void *ptr, size_t size, int access_type,
-			       enum kcsan_value_change value_change, int watchpoint_idx,
-			       u64 old, u64 new, u64 mask);
+			       unsigned long ip, enum kcsan_value_change value_change,
+			       int watchpoint_idx, u64 old, u64 new, u64 mask);
 
 /*
  * No other thread was observed to race with the access, but the data value
  * before and after the stall differs. Reports a race of "unknown origin".
  */
 void kcsan_report_unknown_origin(const volatile void *ptr, size_t size, int access_type,
-				 u64 old, u64 new, u64 mask);
+				 unsigned long ip, u64 old, u64 new, u64 mask);
 
 #endif /* _KERNEL_KCSAN_KCSAN_H */