linux-kernel - Re: [PATCH net-next 3/5] netconsole: append msgid to sysdata

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Message-ID: <CAGSyskW0XHZGHsJ1R2e_Lgh1nG+SJ9Rwk_-nWfU6Xdw5VQTd8A@mail.gmail.com>
Date: Thu, 12 Jun 2025 14:06:48 +0100
From: Gustavo Luiz Duarte <gustavold@...il.com>
To: Breno Leitao <leitao@...ian.org>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Shuah Khan <shuah@...nel.org>, Simon Horman <horms@...nel.org>, Jonathan Corbet <corbet@....net>, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH net-next 3/5] netconsole: append msgid to sysdata

On Wed, Jun 11, 2025 at 4:30 PM Breno Leitao <leitao@...ian.org> wrote:
>
> On Wed, Jun 11, 2025 at 07:36:05AM -0700, Gustavo Luiz Duarte wrote:
> > Add msgcounter to the netconsole_target struct to generate message IDs.
> > If the msgid_enabled attribute is true, increment msgcounter and append
> > msgid=<msgcounter> to sysdata buffer before sending the message.
> >
> > Signed-off-by: Gustavo Luiz Duarte <gustavold@...il.com>
> > ---
> >  drivers/net/netconsole.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> > index 813f50abaf9f..34b61e299eeb 100644
> > --- a/drivers/net/netconsole.c
> > +++ b/drivers/net/netconsole.c
> > @@ -155,6 +155,8 @@ struct netconsole_target {
> >       size_t                  userdata_length;
> >       /* bit-wise with sysdata_feature bits */
> >       u32                     sysdata_fields;
> > +     /* protected by target_list_lock */
> > +     u32                     msgcounter;
> >  #endif
> >       struct netconsole_target_stats stats;
> >       bool                    enabled;
> > @@ -1345,13 +1347,21 @@ static int sysdata_append_release(struct netconsole_target *nt, int offset)
> >                        init_utsname()->release);
> >  }
> >
> > +static int sysdata_append_msgid(struct netconsole_target *nt, int offset)
> > +{
> > +     nt->msgcounter++;
>
> This will eventually wrap. I am wondering if you should use the
> overflow.h helpers to avoid warnings in UBSAN and friends.

Good point. I will send v2 using one of the overflow safe macros.
Thanks for reviewing!

>
> Quick glanced over that filed, I found:
>
>         /**
>         * wrapping_add() - Intentionally perform a wrapping addition
>         * @type: type for result of calculation
>         * @a: first addend
>         * @b: second addend
>         *
>         * Return the potentially wrapped-around addition without
>         * tripping any wrap-around sanitizers that may be enabled.
>         */
>
> > +     return scnprintf(&nt->extradata_complete[offset],
> > +                      MAX_EXTRADATA_ENTRY_LEN, " msgid=%u\n",
> > +                      nt->msgcounter);
> > +}
> > +
> >  /*
> >   * prepare_extradata - append sysdata at extradata_complete in runtime
> >   * @nt: target to send message to
> >   */
> >  static int prepare_extradata(struct netconsole_target *nt)
> >  {
> > -     u32 fields = SYSDATA_CPU_NR | SYSDATA_TASKNAME;
> > +     u32 fields = SYSDATA_CPU_NR | SYSDATA_TASKNAME | SYSDATA_MSGID;
>
> This might be gone now, according to your last patch.,
>
> LGTM.