diff mbox series

[v2,1/3] kernel: make kcov_common_handle consider the current context

Message ID 20201009170202.103512-2-a.nogikh@gmail.com (mailing list archive)
State Not Applicable
Headers show
Series net, mac80211, kernel: enable KCOV remote coverage collection for 802.11 frame handling | expand

Commit Message

Aleksandr Nogikh Oct. 9, 2020, 5:02 p.m. UTC
From: Aleksandr Nogikh <nogikh@google.com>

kcov_common_handle is a method that is used to obtain a "default" KCOV
remote handle of the current process. The handle can later be passed
to kcov_remote_start in order to collect coverage for the processing
that is initiated by one process, but done in another. For details see
Documentation/dev-tools/kcov.rst and comments in kernel/kcov.c.

Presently, if kcov_common_handle is called in a hard IRQ context, it
will return a handle for the interrupted process. This may lead to
unreliable and incorrect coverage collection.

Adjust the behavior of kcov_common_handle in the following way. If it
is called in a task context, return the common handle for the
currently running task. Otherwise, return 0. It will make the returned
value more reliable and also will make it possible to use
kcov_remote_handle in routines that can be called from any context.

Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
---
v2:
* Added this patch to the series.
---
 kernel/kcov.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Andrey Konovalov Oct. 14, 2020, 4:03 p.m. UTC | #1
On Fri, Oct 9, 2020 at 7:02 PM Aleksandr Nogikh <a.nogikh@gmail.com> wrote:
>
> From: Aleksandr Nogikh <nogikh@google.com>
>
> kcov_common_handle is a method that is used to obtain a "default" KCOV
> remote handle of the current process. The handle can later be passed
> to kcov_remote_start in order to collect coverage for the processing
> that is initiated by one process, but done in another. For details see
> Documentation/dev-tools/kcov.rst and comments in kernel/kcov.c.
>
> Presently, if kcov_common_handle is called in a hard IRQ context, it
> will return a handle for the interrupted process. This may lead to
> unreliable and incorrect coverage collection.

FWIW it's the same for soft IRQ context.

>
> Adjust the behavior of kcov_common_handle in the following way. If it
> is called in a task context, return the common handle for the
> currently running task. Otherwise, return 0. It will make the returned
> value more reliable and also will make it possible to use
> kcov_remote_handle in routines that can be called from any context.
>
> Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
> ---
> v2:
> * Added this patch to the series.
> ---
>  kernel/kcov.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/kcov.c b/kernel/kcov.c
> index 6b8368be89c8..80bfe71bbe13 100644
> --- a/kernel/kcov.c
> +++ b/kernel/kcov.c
> @@ -1023,6 +1023,8 @@ EXPORT_SYMBOL(kcov_remote_stop);
>  /* See the comment before kcov_remote_start() for usage details. */
>  u64 kcov_common_handle(void)
>  {
> +       if (!in_task())
> +               return 0;
>         return current->kcov_handle;
>  }
>  EXPORT_SYMBOL(kcov_common_handle);
> --
> 2.28.0.1011.ga647a8990f-goog
>

Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
diff mbox series

Patch

diff --git a/kernel/kcov.c b/kernel/kcov.c
index 6b8368be89c8..80bfe71bbe13 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -1023,6 +1023,8 @@  EXPORT_SYMBOL(kcov_remote_stop);
 /* See the comment before kcov_remote_start() for usage details. */
 u64 kcov_common_handle(void)
 {
+	if (!in_task())
+		return 0;
 	return current->kcov_handle;
 }
 EXPORT_SYMBOL(kcov_common_handle);