linux-kernel - Re: [PATCH v2] kdb: remove unnecessary null check of dbg_io

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Message-ID: <CAD=FV=XWYKqHEMDt-0PYHty_syJ9MO6Oz8DVBbacNZS5zGXk9A@mail.gmail.com>
Date:   Mon, 29 Jun 2020 14:16:39 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Cengiz Can <cengiz@...nel.wtf>
Cc:     Daniel Thompson <daniel.thompson@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        kgdb-bugreport@...ts.sourceforge.net,
        LKML <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sumit Garg <sumit.garg@...aro.org>
Subject: Re: [PATCH v2] kdb: remove unnecessary null check of dbg_io_ops

Hi,

On Mon, Jun 29, 2020 at 1:50 PM Cengiz Can <cengiz@...nel.wtf> wrote:
>
> `kdb_msg_write` operates on a global `struct kgdb_io *` called
> `dbg_io_ops`.
>
> It's initialized in `debug_core.c` and checked throughout the debug
> flow.
>
> There's a null check in `kdb_msg_write` which triggers static analyzers
> and gives the (almost entirely wrong) impression that it can be null.
>
> Coverity scanner caught this as CID 1465042.
>
> I have removed the unnecessary null check and eliminated false-positive
> forward null dereference warning.
>
> Signed-off-by: Cengiz Can <cengiz@...nel.wtf>
> ---
>  kernel/debug/kdb/kdb_io.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
> index 683a799618ad..4ac59a4fbeec 100644
> --- a/kernel/debug/kdb/kdb_io.c
> +++ b/kernel/debug/kdb/kdb_io.c
> @@ -549,14 +549,12 @@ static void kdb_msg_write(const char *msg, int msg_len)
>         if (msg_len == 0)
>                 return;
>
> -       if (dbg_io_ops) {
> -               const char *cp = msg;
> -               int len = msg_len;
> +       const char *cp = msg;
> +       int len = msg_len;

kernel/debug/kdb/kdb_io.c:552:14:
warning: ISO C90 forbids mixing declarations and code
[-Wdeclaration-after-statement]

-Doug