Greg Kroah-Hartman
2019-Oct-17 20:29 UTC
[PATCH RFC 2/3] usb, kcov: collect coverage from hub_event
On Thu, Oct 17, 2019 at 09:06:56PM +0200, Andrey Konovalov wrote:> On Thu, Oct 17, 2019 at 8:19 PM Greg Kroah-Hartman > <gregkh at linuxfoundation.org> wrote: > > > > On Thu, Oct 17, 2019 at 07:44:14PM +0200, Andrey Konovalov wrote: > > > This patch adds kcov_remote_start/kcov_remote_stop annotations to the > > > hub_event function, which is responsible for processing events on USB > > > buses, in particular events that happen during USB device enumeration. > > > Each USB bus gets a unique id, which can be used to attach a kcov device > > > to a particular USB bus for coverage collection. > > > > > > Signed-off-by: Andrey Konovalov <andreyknvl at google.com> > > > --- > > > drivers/usb/core/hub.c | 4 ++++ > > > include/linux/kcov.h | 1 + > > > include/uapi/linux/kcov.h | 7 +++++++ > > > 3 files changed, 12 insertions(+) > > > > > > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c > > > index 236313f41f4a..03a40e41b099 100644 > > > --- a/drivers/usb/core/hub.c > > > +++ b/drivers/usb/core/hub.c > > > @@ -5374,6 +5374,8 @@ static void hub_event(struct work_struct *work) > > > hub_dev = hub->intfdev; > > > intf = to_usb_interface(hub_dev); > > > > > > + kcov_remote_start(kcov_remote_handle_usb(hdev->bus->busnum)); > > > + > > > dev_dbg(hub_dev, "state %d ports %d chg %04x evt %04x\n", > > > hdev->state, hdev->maxchild, > > > /* NOTE: expects max 15 ports... */ > > > @@ -5480,6 +5482,8 @@ static void hub_event(struct work_struct *work) > > > /* Balance the stuff in kick_hub_wq() and allow autosuspend */ > > > usb_autopm_put_interface(intf); > > > kref_put(&hub->kref, hub_release); > > > + > > > + kcov_remote_stop(); > > > } > > > > > > static const struct usb_device_id hub_id_table[] = { > > > diff --git a/include/linux/kcov.h b/include/linux/kcov.h > > > index 702672d98d35..38a47e0b67c2 100644 > > > --- a/include/linux/kcov.h > > > +++ b/include/linux/kcov.h > > > @@ -30,6 +30,7 @@ void kcov_task_exit(struct task_struct *t); > > > /* > > > * Reserved handle ranges: > > > * 0000000000000000 - 0000ffffffffffff : common handles > > > + * 0001000000000000 - 0001ffffffffffff : USB subsystem handles > > > > So how many bits are you going to have for any in-kernel tasks? Aren't > > you going to run out quickly? > > With these patches we only collect coverage from hub_event threads, > and we need one ID per USB bus, the number of which is quite limited. > But then we might want to collect coverage from other parts of the USB > subsystem, so we might need more IDs. I don't expect the number of > different subsystem from which we want to collect coverage to be > large, so the idea here is to use 2 bytes of an ID to denote the > subsystem, and the other 6 to denote different coverage collection > sections within it. > > But overall, which encoding scheme to use here is a good question. > Ideas are welcome. > > > > */ > > > void kcov_remote_start(u64 handle); > > > void kcov_remote_stop(void); > > > diff --git a/include/uapi/linux/kcov.h b/include/uapi/linux/kcov.h > > > index 46f78f716ca9..45c9ae59cebc 100644 > > > --- a/include/uapi/linux/kcov.h > > > +++ b/include/uapi/linux/kcov.h > > > @@ -43,4 +43,11 @@ enum { > > > #define KCOV_CMP_SIZE(n) ((n) << 1) > > > #define KCOV_CMP_MASK KCOV_CMP_SIZE(3) > > > > > > +#define KCOV_REMOTE_HANDLE_USB 0x0001000000000000ull > > > + > > > +static inline __u64 kcov_remote_handle_usb(unsigned int bus) > > > +{ > > > + return KCOV_REMOTE_HANDLE_USB + (__u64)bus; > > > +} > > > > Why is this function in a uapi .h file? What userspace code would call > > this? > > A userspace process that wants to collect coverage from USB bus # N > needs to pass kcov_remote_handle_usb(N) into KCOV_REMOTE_ENABLE ioctl.Ugh, ok. Then you should make "unsigned int bus" a __u64 so that this actually will work on all kernels properly. thanks, greg k-h