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

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Date:   Tue, 30 Jun 2020 01:10:19 +0300
From:   Cengiz Can <cengiz@...nel.wtf>
To:     Doug Anderson <dianders@...omium.org>
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


On June 30, 2020 00:16:54 Doug Anderson <dianders@...omium.org> wrote:

> 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]

Oops!

Sorry for that..

I admit I didn't compile check my second attempt.

/me ducks and covers

Will fix it asap.

Thanks!

>
> -Doug