[PATCH RFC 2/3] usb, kcov: collect coverage from hub_event

[Andrey Konovalov]

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@xxxxxxxxxx>
---
 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
  */
 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;
+}
+
 #endif /* _LINUX_KCOV_IOCTLS_H */
-- 
2.23.0.866.gb869b98d4c-goog