[005/127] kcov: use t->kcov_mode as enabled indicator

Commit Message

Andrew Morton June 4, 2020, 11:46 p.m. UTC

From: Andrey Konovalov <[e-mail]>
Subject: kcov: use t->kcov_mode as enabled indicator

Currently kcov_remote_start() and kcov_remote_stop() check t->kcov to find
out whether the coverage is already being collected by the current task. 
Use t->kcov_mode for that instead.  This doesn't change the overall
behavior in any way, but serves as a preparation for the following softirq
coverage collection support patch.

Link: http://lkml.kernel.org/r/f7[e-mail]
Link: http://lkml.kernel.org/r/ee[e-mail]
Signed-off-by: Andrey Konovalov <[e-mail]>
Reviewed-by: Dmitry Vyukov <[e-mail]>
Cc: Alan Stern <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Marco Elver <[e-mail]>
Cc: Andrey Konovalov <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 kernel/kcov.c |   34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

Patch

--- a/kernel/kcov.c~kcov-use-t-kcov_mode-as-enabled-indicator
+++ a/kernel/kcov.c
@@ -746,26 +746,33 @@  static const struct file_operations kcov
  * In turns kcov_remote_stop() clears those pointers from task_struct to stop
  * collecting coverage and copies all collected coverage into the kcov area.
  */
+
+static inline bool kcov_mode_enabled(unsigned int mode)
+{
+	return (mode & ~KCOV_IN_CTXSW) != KCOV_MODE_DISABLED;
+}
+
 void kcov_remote_start(u64 handle)
 {
+	struct task_struct *t = current;
 	struct kcov_remote *remote;
 	struct kcov *kcov;
+	unsigned int mode;
 	void *area;
-	struct task_struct *t;
 	unsigned int size;
-	enum kcov_mode mode;
 	int sequence;
 
 	if (WARN_ON(!kcov_check_handle(handle, true, true, true)))
 		return;
 	if (WARN_ON(!in_task()))
 		return;
-	t = current;
+
 	/*
 	 * Check that kcov_remote_start is not called twice
 	 * nor called by user tasks (with enabled kcov).
 	 */
-	if (WARN_ON(t->kcov))
+	mode = READ_ONCE(t->kcov_mode);
+	if (WARN_ON(kcov_mode_enabled(mode)))
 		return;
 
 	kcov_debug("handle = %llx\n", handle);
@@ -863,13 +870,20 @@  static void kcov_move_area(enum kcov_mod
 void kcov_remote_stop(void)
 {
 	struct task_struct *t = current;
-	struct kcov *kcov = t->kcov;
-	void *area = t->kcov_area;
-	unsigned int size = t->kcov_size;
-	int sequence = t->kcov_sequence;
+	struct kcov *kcov;
+	unsigned int mode;
+	void *area;
+	unsigned int size;
+	int sequence;
 
-	if (!kcov)
-		return;
+	mode = READ_ONCE(t->kcov_mode);
+	barrier();
+	if (!kcov_mode_enabled(mode))
+		return;
+	kcov = t->kcov;
+	area = t->kcov_area;
+	size = t->kcov_size;
+	sequence = t->kcov_sequence;
 
 	kcov_stop(t);