instrumented.h: Introduce read-write instrumentation hooks

Introduce read-write instrumentation hooks, to more precisely denote an
operation's behaviour.

KCSAN is able to distinguish compound instrumentation, and with the new
instrumentation we then benefit from improved reporting. More
importantly, read-write compound operations should not implicitly be
treated as atomic, if they aren't actually atomic.

Acked-by: Peter Zijlstra (Intel) <[e-mail]>
Signed-off-by: Marco Elver <[e-mail]>
Signed-off-by: Paul E. McKenney <[e-mail]>

include/linux/instrumented.h

···
 }
 
 /**
+ * instrument_read_write - instrument regular read-write access
+ *
+ * Instrument a regular write access. The instrumentation should be inserted
+ * before the actual write happens.
+ *
+ * @ptr address of access
+ * @size size of access
+ */
+static __always_inline void instrument_read_write(const volatile void *v, size_t size)
+{
+	kasan_check_write(v, size);
+	kcsan_check_read_write(v, size);
+}
+
+/**
  * instrument_atomic_read - instrument atomic read access
  *
  * Instrument an atomic read access. The instrumentation should be inserted
···
 {
 	kasan_check_write(v, size);
 	kcsan_check_atomic_write(v, size);
+}
+
+/**
+ * instrument_atomic_read_write - instrument atomic read-write access
+ *
+ * Instrument an atomic read-write access. The instrumentation should be
+ * inserted before the actual write happens.
+ *
+ * @ptr address of access
+ * @size size of access
+ */
+static __always_inline void instrument_atomic_read_write(const volatile void *v, size_t size)
+{
+	kasan_check_write(v, size);
+	kcsan_check_atomic_read_write(v, size);
 }
 
 /**