On Thu, Mar 26, 2020 at 3:44 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> ---
> 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
>
