@@ -1623,6 +1623,7 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
struct usb_hcd *hcd = bus_to_hcd(urb->dev->bus);
struct usb_anchor *anchor = urb->anchor;
int status = urb->unlinked;
+ unsigned long flags;
urb->hcpriv = NULL;
if (unlikely((urb->transfer_flags & URB_SHORT_NOT_OK) &&
@@ -1640,13 +1641,14 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
/* pass ownership to the completion handler */
urb->status = status;
/*
- * This function can be called in task context inside another remote
- * coverage collection section, but kcov doesn't support that kind of
- * recursion yet. Only collect coverage in softirq context for now.
+ * Only collect coverage in the softirq context and disable interrupts
+ * to avoid scenarios with nested remote coverage collection sections
+ * that KCOV does not support.
+ * See the comment next to kcov_remote_start_usb_softirq() for details.
*/
- kcov_remote_start_usb_softirq((u64)urb->dev->bus->busnum);
+ flags = kcov_remote_start_usb_softirq((u64)urb->dev->bus->busnum);
urb->complete(urb);
- kcov_remote_stop_softirq();
+ kcov_remote_stop_softirq(flags);
usb_anchor_resume_wakeups(anchor);
atomic_dec(&urb->use_count);
@@ -55,21 +55,47 @@ static inline void kcov_remote_start_usb(u64 id)
/*
* The softirq flavor of kcov_remote_*() functions is introduced as a temporary
- * work around for kcov's lack of nested remote coverage sections support in
- * task context. Adding support for nested sections is tracked in:
- * https://bugzilla.kernel.org/show_bug.cgi?id=210337
+ * workaround for KCOV's lack of nested remote coverage sections support.
+ *
+ * Adding support is tracked in https://bugzilla.kernel.org/show_bug.cgi?id=210337.
+ *
+ * kcov_remote_start_usb_softirq():
+ *
+ * 1. Only collects coverage when called in the softirq context. This allows
+ * avoiding nested remote coverage collection sections in the task context.
+ * For example, USB/IP calls usb_hcd_giveback_urb() in the task context
+ * within an existing remote coverage collection section. Thus, KCOV should
+ * not attempt to start collecting coverage within the coverage collection
+ * section in __usb_hcd_giveback_urb() in this case.
+ *
+ * 2. Disables interrupts for the duration of the coverage collection section.
+ * This allows avoiding nested remote coverage collection sections in the
+ * softirq context (a softirq might occur during the execution of a work in
+ * the BH workqueue, which runs with in_serving_softirq() > 0).
+ * For example, usb_giveback_urb_bh() runs in the BH workqueue with
+ * interrupts enabled, so __usb_hcd_giveback_urb() might be interrupted in
+ * the middle of its remote coverage collection section, and the interrupt
+ * handler might invoke __usb_hcd_giveback_urb() again.
*/
-static inline void kcov_remote_start_usb_softirq(u64 id)
+static inline unsigned long kcov_remote_start_usb_softirq(u64 id)
{
- if (in_serving_softirq())
+ unsigned long flags = 0;
+
+ if (in_serving_softirq()) {
+ local_irq_save(flags);
kcov_remote_start_usb(id);
+ }
+
+ return flags;
}
-static inline void kcov_remote_stop_softirq(void)
+static inline void kcov_remote_stop_softirq(unsigned long flags)
{
- if (in_serving_softirq())
+ if (in_serving_softirq()) {
kcov_remote_stop();
+ local_irq_restore(flags);
+ }
}
#ifdef CONFIG_64BIT
@@ -103,8 +129,11 @@ static inline u64 kcov_common_handle(void)
}
static inline void kcov_remote_start_common(u64 id) {}
static inline void kcov_remote_start_usb(u64 id) {}
-static inline void kcov_remote_start_usb_softirq(u64 id) {}
-static inline void kcov_remote_stop_softirq(void) {}
+static inline unsigned long kcov_remote_start_usb_softirq(u64 id)
+{
+ return 0;
+}
+static inline void kcov_remote_stop_softirq(unsigned long flags) {}
#endif /* CONFIG_KCOV */
#endif /* _LINUX_KCOV_H */