linux-kernel - [PATCH v2] kcov, usb: hide in_serving_softirq checks in __usb_hcd_giveback

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Message-Id: <04978189d40307e979be61c458f4944b61134198.1610035117.git.andreyknvl@google.com>
Date:   Thu,  7 Jan 2021 17:01:44 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v2] kcov, usb: hide in_serving_softirq checks in __usb_hcd_giveback_urb

Done opencode in_serving_softirq() checks in __usb_hcd_giveback_urb() to
avoid cluttering the code, hide them in kcov helpers instead.

Fixes: aee9ddb1d371 ("kcov, usb: only collect coverage from __usb_hcd_giveback_urb in softirq")
Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---

Changes v1->v2:
- Fix a typo in the commit description and in a comment in the patch.

---
 drivers/usb/core/hcd.c |  8 +++-----
 include/linux/kcov.h   | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 60886a7464c3..ad5a0f405a75 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1649,14 +1649,12 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
 	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
+	 * coverage collection section, but kcov doesn't support that kind of
 	 * recursion yet. Only collect coverage in softirq context for now.
 	 */
-	if (in_serving_softirq())
-		kcov_remote_start_usb((u64)urb->dev->bus->busnum);
+	kcov_remote_start_usb_softirq((u64)urb->dev->bus->busnum);
 	urb->complete(urb);
-	if (in_serving_softirq())
-		kcov_remote_stop();
+	kcov_remote_stop_softirq();
 
 	usb_anchor_resume_wakeups(anchor);
 	atomic_dec(&urb->use_count);
diff --git a/include/linux/kcov.h b/include/linux/kcov.h
index a10e84707d82..18306ef8ad5a 100644
--- a/include/linux/kcov.h
+++ b/include/linux/kcov.h
@@ -52,6 +52,25 @@ static inline void kcov_remote_start_usb(u64 id)
 	kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_USB, id));
 }
 
+/*
+ * The softirq flavor of kcov_remote_*() functions is introduced as a temporary
+ * workaround for kcov's lack of nested remote coverage sections support in
+ * task context. Adding suport for nested sections is tracked in:
+ * https://bugzilla.kernel.org/show_bug.cgi?id=210337
+ */
+
+static inline void kcov_remote_start_usb_softirq(u64 id)
+{
+	if (in_serving_softirq())
+		kcov_remote_start_usb(id);
+}
+
+static inline void kcov_remote_stop_softirq(void)
+{
+	if (in_serving_softirq())
+		kcov_remote_stop();
+}
+
 #else
 
 static inline void kcov_task_init(struct task_struct *t) {}
@@ -66,6 +85,8 @@ 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) {}
 
 #endif /* CONFIG_KCOV */
 #endif /* _LINUX_KCOV_H */
-- 
2.29.2.729.g45daf8777d-goog