kcsan: Refactor passing watchpoint/other_info

The `watchpoint_idx` argument to kcsan_report() isn't meaningful for
races which were not detected by a watchpoint, and it would be clearer
if callers passed the other_info directly so that a NULL value can be
passed in this case.

Given that callers manipulate their watchpoints before passing the index
into kcsan_report_*(), and given we index the `other_infos` array using
this before we sanity-check it, the subsequent sanity check isn't all
that useful.

Let's remove the `watchpoint_idx` sanity check, and move the job of
finding the `other_info` out of kcsan_report().

Other than the removal of the check, there should be no functional
change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/kcsan/report.c

@@ -600,7 +600,7 @@ static noinline bool prepare_report(unsigned long *flags,
 
 static void kcsan_report(const volatile void *ptr, size_t size, int access_type,
 			 enum kcsan_value_change value_change,
-			 enum kcsan_report_type type, int watchpoint_idx)
+			 enum kcsan_report_type type, struct other_info *other_info)
 {
 	unsigned long flags = 0;
 	const struct access_info ai = {
@@ -610,12 +610,8 @@ static void kcsan_report(const volatile void *ptr, size_t size, int access_type,
 		.task_pid	= in_task() ? task_pid_nr(current) : -1,
 		.cpu_id		= raw_smp_processor_id()
 	};
-	struct other_info *other_info = type == KCSAN_REPORT_RACE_UNKNOWN_ORIGIN
-					? NULL : &other_infos[watchpoint_idx];
 
 	kcsan_disable_current();
-	if (WARN_ON(watchpoint_idx < 0 || watchpoint_idx >= ARRAY_SIZE(other_infos)))
-		goto out;
 
 	/*
 	 * Because we may generate reports when we're in scheduler code, the use
@@ -642,7 +638,6 @@ static void kcsan_report(const volatile void *ptr, size_t size, int access_type,
 	}
 
 	lockdep_on();
-out:
 	kcsan_enable_current();
 }
 
@@ -650,18 +645,18 @@ void kcsan_report_set_info(const volatile void *ptr, size_t size, int access_typ
 			   int watchpoint_idx)
 {
 	kcsan_report(ptr, size, access_type, KCSAN_VALUE_CHANGE_MAYBE,
-		     KCSAN_REPORT_CONSUMED_WATCHPOINT, watchpoint_idx);
+		     KCSAN_REPORT_CONSUMED_WATCHPOINT, &other_infos[watchpoint_idx]);
 }
 
 void kcsan_report_known_origin(const volatile void *ptr, size_t size, int access_type,
 			       enum kcsan_value_change value_change, int watchpoint_idx)
 {
 	kcsan_report(ptr, size, access_type, value_change,
-		     KCSAN_REPORT_RACE_SIGNAL, watchpoint_idx);
+		     KCSAN_REPORT_RACE_SIGNAL, &other_infos[watchpoint_idx]);
 }
 
 void kcsan_report_unknown_origin(const volatile void *ptr, size_t size, int access_type)
 {
 	kcsan_report(ptr, size, access_type, KCSAN_VALUE_CHANGE_TRUE,
-		     KCSAN_REPORT_RACE_UNKNOWN_ORIGIN, 0);
+		     KCSAN_REPORT_RACE_UNKNOWN_ORIGIN, NULL);
 }