kcov, usbip: collect coverage from vhci_rx_loop

Add kcov_remote_start()/kcov_remote_stop() annotations to the
vhci_rx_loop() function, which is responsible for parsing USB/IP packets
coming into USB/IP client.

Since vhci_rx_loop() threads are spawned per vhci_hcd device instance, the
common kcov handle is used for kcov_remote_start()/stop() annotations
(see Documentation/dev-tools/kcov.rst for details). As the result kcov
can now be used to collect coverage from vhci_rx_loop() threads.

Co-developed-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Nazime Hande Harputluoglu <handeharputlu@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://lore.kernel.org/r/f8114050f8d65aa0bc801318b1db532d9f432447.1606175386.git.andreyknvl@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/usbip/usbip_common.h

@@ -277,6 +277,10 @@ struct usbip_device {
 		void (*reset)(struct usbip_device *);
 		void (*unusable)(struct usbip_device *);
 	} eh_ops;
+
+#ifdef CONFIG_KCOV
+	u64 kcov_handle;
+#endif
 };
 
 #define kthread_get_run(threadfn, data, namefmt, ...)			   \
@@ -337,4 +341,29 @@ static inline int interface_to_devnum(struct usb_interface *interface)
 	return udev->devnum;
 }
 
+#ifdef CONFIG_KCOV
+
+static inline void usbip_kcov_handle_init(struct usbip_device *ud)
+{
+	ud->kcov_handle = kcov_common_handle();
+}
+
+static inline void usbip_kcov_remote_start(struct usbip_device *ud)
+{
+	kcov_remote_start_common(ud->kcov_handle);
+}
+
+static inline void usbip_kcov_remote_stop(void)
+{
+	kcov_remote_stop();
+}
+
+#else /* CONFIG_KCOV */
+
+static inline void usbip_kcov_handle_init(struct usbip_device *ud) { }
+static inline void usbip_kcov_remote_start(struct usbip_device *ud) { }
+static inline void usbip_kcov_remote_stop(void) { }
+
+#endif /* CONFIG_KCOV */
+
 #endif /* __USBIP_COMMON_H */

drivers/usb/usbip/vhci_rx.c

@@ -261,7 +261,9 @@ int vhci_rx_loop(void *data)
 		if (usbip_event_happened(ud))
 			break;
 
+		usbip_kcov_remote_start(ud);
 		vhci_rx_pdu(ud);
+		usbip_kcov_remote_stop();
 	}
 
 	return 0;

drivers/usb/usbip/vhci_sysfs.c

@@ -383,6 +383,7 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 	vdev->ud.sockfd     = sockfd;
 	vdev->ud.tcp_socket = socket;
 	vdev->ud.status     = VDEV_ST_NOTASSIGNED;
+	usbip_kcov_handle_init(&vdev->ud);
 
 	spin_unlock(&vdev->ud.lock);
 	spin_unlock_irqrestore(&vhci->lock, flags);