Re: [PATCH v4 7/7] usb: core: kcov: collect coverage from usb complete callback

[Dmitry Vyukov]

On Thu, Mar 26, 2020 at 3:44 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> This patch adds kcov_remote_start/stop() callbacks around the urb
> complete() callback that is executed in softirq context when dummy_hcd
> is in use. As the result, kcov can be used to collect coverage from those
> callbacks, which is used to facilitate coverage-guided fuzzing with
> syzkaller.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>

> ---
>  drivers/usb/core/hcd.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index aa45840d8273..de624c47e190 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -31,6 +31,7 @@
>  #include <linux/types.h>
>  #include <linux/genalloc.h>
>  #include <linux/io.h>
> +#include <linux/kcov.h>
>
>  #include <linux/phy/phy.h>
>  #include <linux/usb.h>
> @@ -1645,7 +1646,9 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
>
>         /* pass ownership to the completion handler */
>         urb->status = status;
> +       kcov_remote_start_usb((u64)urb->dev->bus->busnum);
>         urb->complete(urb);
> +       kcov_remote_stop();
>
>         usb_anchor_resume_wakeups(anchor);
>         atomic_dec(&urb->use_count);
> --
> 2.26.0.rc2.310.g2932bb562d-goog
>