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

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Date:   Thu, 12 Dec 2019 13:15:29 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Andrey Konovalov <andreyknvl@...gle.com>
cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-usb@...r.kernel.org>, <linux-input@...r.kernel.org>,
        <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 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.

Alan Stern