Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:8 as permitted sender) client-ip=2620:137:e000::3:8;
MIME-Version: 1.0
References: <20231103131011.1316396-1-lb@semihalf.com> <20231103131011.1316396-8-lb@semihalf.com>
In-Reply-To: <20231103131011.1316396-8-lb@semihalf.com>
From:   jim.cromie@gmail.com
Date:   Fri, 3 Nov 2023 19:49:02 -0600
Message-ID: <CAJfuBxzWSyw-Xp3k5WzOexbRZFydCUp_nX4A_BZs8Gq0OE2U7Q@mail.gmail.com>
Subject: Re: [PATCH v1 07/12] dyndbg: repack struct _ddebug
To:     =?UTF-8?Q?=C5=81ukasz_Bartosik?= <lb@semihalf.com>
Cc:     Jason Baron <jbaron@akamai.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Douglas Anderson <dianders@chromium.org>,
        Guenter Roeck <groeck@google.com>,
        Yaniv Tzoreff <yanivt@google.com>,
        Benson Leung <bleung@google.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Vincent Whitchurch <vincent.whitchurch@axis.com>,
        Pekka Paalanen <ppaalanen@gmail.com>,
        Sean Paul <seanpaul@chromium.org>,
        Daniel Vetter <daniel@ffwll.ch>, linux-kernel@vger.kernel.org,
        upstream@semihalf.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Fri, Nov 3, 2023 at 7:10=E2=80=AFAM =C5=81ukasz Bartosik <lb@semihalf.co=
m> wrote:
>
> From: Jim Cromie <jim.cromie@gmail.com>
>
> Move the JUMP_LABEL to the top of the struct, since theyre both
> align(8) and this closes a pahole (unfortunately trading for padding,
> but still).
>
> Signed-off-by: Jim Cromie <jim.cromie@gmail.com>

let me add, I havent really tested this, nevermind thorough.
specifically, I didnt look for any offset dependence on the static-key
inside their container.
Conversely, maybe theres a free default or something in there.

> ---
>  include/linux/dynamic_debug.h | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.=
h
> index 497130816e9c..b9237e4ecd1b 100644
> --- a/include/linux/dynamic_debug.h
> +++ b/include/linux/dynamic_debug.h
> @@ -14,6 +14,12 @@
>   * the special section is treated as an array of these.
>   */
>  struct _ddebug {
> +#ifdef CONFIG_JUMP_LABEL
> +       union {
> +               struct static_key_true dd_key_true;
> +               struct static_key_false dd_key_false;
> +       } key;
> +#endif
>         /*
>          * These fields are used to drive the user interface
>          * for selecting and displaying debug callsites.
> @@ -53,12 +59,6 @@ struct _ddebug {
>  #define _DPRINTK_FLAGS_DEFAULT 0
>  #endif
>         unsigned int flags:8;
> -#ifdef CONFIG_JUMP_LABEL
> -       union {
> -               struct static_key_true dd_key_true;
> -               struct static_key_false dd_key_false;
> -       } key;
> -#endif
>  } __attribute__((aligned(8)));
>
>  enum class_map_type {
> --
> 2.42.0.869.gea05f2083d-goog
>