Re: [PATCH RFC 1/2] kcov: collect coverage from interrupts

From: Andrey Konovalov <andreyknvl@google.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Kosina <jikos@kernel.org>,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	USB list <linux-usb@vger.kernel.org>,
	linux-input@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	Alexander Potapenko <glider@google.com>,
	Marco Elver <elver@google.com>
Subject: Re: [PATCH RFC 1/2] kcov: collect coverage from interrupts
Date: Fri, 13 Dec 2019 13:08:53 +0100	[thread overview]
Message-ID: <CAAeHK+yOBcNz_iopRs6PEu=1-rZn6Gkm+Urq+iVBFQeSjSXqNA@mail.gmail.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1912121313030.1352-100000@iolanthe.rowland.org>

On Thu, Dec 12, 2019 at 7:15 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Thu, 12 Dec 2019, Andrey Konovalov wrote:
>
> > This change extends kcov remote coverage support to allow collecting
> > coverage from interrupts in addition to kernel background threads.
> >
> > To collect coverage from code that is executed in interrupt context, a
> > part of that code has to be annotated with kcov_remote_start/stop() in a
> > similar way as how it is done for global kernel background threads. Then
> > the handle used for the annotations has to be passed to the
> > KCOV_REMOTE_ENABLE ioctl.
> >
> > Internally this patch adjusts the __sanitizer_cov_trace_pc() compiler
> > inserted callback to not bail out when called from interrupt context.
> > kcov_remote_start/stop() are updated to save/restore the current per
> > task kcov state in a per-cpu area (in case the interrupt came when the
> > kernel was already collecting coverage in task context). Coverage from
> > interrupts is collected into pre-allocated per-cpu areas, whose size is
> > controlled by the new CONFIG_KCOV_IRQ_AREA_SIZE.
> >
> > This patch also cleans up some of kcov debug messages.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > ---
>
> > diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
> > index 4c9d1e49d5ed..faf84ada71a5 100644
> > --- a/drivers/usb/gadget/udc/dummy_hcd.c
> > +++ b/drivers/usb/gadget/udc/dummy_hcd.c
> > @@ -38,6 +38,7 @@
> >  #include <linux/usb/gadget.h>
> >  #include <linux/usb/hcd.h>
> >  #include <linux/scatterlist.h>
> > +#include <linux/kcov.h>
> >
> >  #include <asm/byteorder.h>
> >  #include <linux/io.h>
>
> That's the only change to this driver.  As such, it doesn't appear to
> be needed, judging by the patch description.

Right, will fix in the next version, thanks!