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

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Date:   Tue, 17 Dec 2019 12:35:13 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        USB list <linux-usb@...r.kernel.org>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>
Subject: Re: [PATCH RFC 1/2] kcov: collect coverage from interrupts

On Tue, Dec 17, 2019 at 12:16 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
> > > On Thu, Dec 12, 2019 at 7:15 PM Alan Stern <stern@...land.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@...gle.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!
> >
> > Please also post a github or gerrit link. These small scraps of
> > changes without context and better visualisation are extremely hard to
> > review meaningfully.
>
> The link is in the cover letter:
>
> https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/2224/1

Sorry, missed. Now I can read it!