usb, kcov: collect coverage from hub_event

Add 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.

Since hub_event() is run in a global background kernel thread (see
Documentation/dev-tools/kcov.rst for details), each USB bus gets a
unique global handle from the USB subsystem kcov handle range.  As the
result kcov can now be used to collect coverage from events that happen
on a particular USB bus.

[[email protected]: avoid patch conflicts to make life easier for Andrew]
Link: http://lkml.kernel.org/r/de4fe1c219db2d002d905dc1736e2a3bfa1db997.1572366574.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <[email protected]>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Cc: Alan Stern <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Anders Roxell <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: David Windsor <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Elena Reshetova <[email protected]>
Cc: Jason Wang <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Steven Rostedt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: xairy

drivers/usb/core/hub.c

@@ -18,6 +18,7 @@
 #include <linux/sched/mm.h>
 #include <linux/list.h>
 #include <linux/slab.h>
+#include <linux/kcov.h>
 #include <linux/ioctl.h>
 #include <linux/usb.h>
 #include <linux/usbdevice_fs.h>
@@ -5484,6 +5485,8 @@ static void hub_event(struct work_struct *work)
 	hub_dev = hub->intfdev;
 	intf = to_usb_interface(hub_dev);
 
+	kcov_remote_start_usb((u64)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... */
@@ -5590,6 +5593,8 @@ 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[] = {