linux-kernel - [PATCH v2 3/3] usb: core: kcov: collect coverage from usb complete callback

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Message-Id: <32bce32c8b88c2f88cd0a8acfcdb5d3a6e894632.1583778264.git.andreyknvl@google.com>
Date:   Mon,  9 Mar 2020 19:27:06 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v2 3/3] usb: core: kcov: collect coverage from usb complete callback

This patch adds kcov_remote_start/stop() callbacks around the urb
complete() callback that is executed in softirq context when dummy_hcd
is in use. As the result, kcov can be used to collect coverage from those
those callbacks, which is used to facilitate coverage-guided fuzzing with
syzkaller.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 drivers/usb/core/hcd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index aa45840d8273..de624c47e190 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -31,6 +31,7 @@
 #include <linux/types.h>
 #include <linux/genalloc.h>
 #include <linux/io.h>
+#include <linux/kcov.h>
 
 #include <linux/phy/phy.h>
 #include <linux/usb.h>
@@ -1645,7 +1646,9 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
 
 	/* pass ownership to the completion handler */
 	urb->status = status;
+	kcov_remote_start_usb((u64)urb->dev->bus->busnum);
 	urb->complete(urb);
+	kcov_remote_stop();
 
 	usb_anchor_resume_wakeups(anchor);
 	atomic_dec(&urb->use_count);
-- 
2.25.1.481.gfbce0eb801-goog