linux-kernel - Re: [PATCH v2] kdb: Make the internal env 'KDBFLAGS' undefinable

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Message-ID: <20200519114008.lmdf44zmgcmnf27c@holly.lan>
Date:   Tue, 19 May 2020 12:40:08 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Wei Li <liwei391@...wei.com>
Cc:     Doug Anderson <dianders@...omium.org>,
        Jason Wessel <jason.wessel@...driver.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        kgdb-bugreport@...ts.sourceforge.net,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kdb: Make the internal env 'KDBFLAGS' undefinable

On Sat, May 16, 2020 at 05:26:06PM +0800, Wei Li wrote:
> 'KDBFLAGS' is an internal variable of kdb, it is combined by 'KDBDEBUG'
> and state flags. But the user can define an environment variable named
> 'KDBFLAGS' too, so let's make it undefinable to avoid confusion.
> 
> Signed-off-by: Wei Li <liwei391@...wei.com>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>

I took a quick look at this and find myself thinking of KDBFLAGS as
something of a misfeature.

I think I'd rather get kdb_env to show the value we wrote into
KDBDEBUG.

Sure this means we cannot use KDBDEBUG to look at the least significant
16-bits but I think anyone who is debugging kdb itself should know
enough to use `md4c1 kdb_flags` to read those anyway.


Daniel.



> ---
> v1 -> v2:
>  - Fix lack of braces.
> 
>  kernel/debug/kdb/kdb_main.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
> index 4fc43fb17127..75b798340300 100644
> --- a/kernel/debug/kdb/kdb_main.c
> +++ b/kernel/debug/kdb/kdb_main.c
> @@ -423,6 +423,8 @@ int kdb_set(int argc, const char **argv)
>  			| (debugflags << KDB_DEBUG_FLAG_SHIFT);
>  
>  		return 0;
> +	} else if (strcmp(argv[1], "KDBFLAGS") == 0) {
> +		return KDB_NOPERM;
>  	}
>  
>  	/*
> -- 
> 2.17.1
>