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Subject[PATCH v4 5/7] kcov: use t->kcov_mode as enabled indicator
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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.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
kernel/kcov.c | 32 +++++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/kernel/kcov.c b/kernel/kcov.c
index b985b7a72870..e43f06b5b2e4 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -746,26 +746,33 @@ static const struct file_operations kcov_fops = {
* 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_mode mode, void *dst_area,
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)
+ 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);

--
2.26.0.rc2.310.g2932bb562d-goog
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