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Message-ID: <9ee753e9d0b4d8fbab431b7f4761c59586f1a3f2.camel@perches.com>
Subject: Re: [PATCH v2] checkpatch: Warn if trace_printk and friends are
 called
From:   Joe Perches <joe@perches.com>
To:     Nicolas Boichat <drinkcat@chromium.org>,
        Andy Whitcroft <apw@canonical.com>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Date:   Tue, 25 Aug 2020 08:54:48 -0700
In-Reply-To: <20200825193600.v2.1.I723c43c155f02f726c97501be77984f1e6bb740a@changeid>
References: <20200825193600.v2.1.I723c43c155f02f726c97501be77984f1e6bb740a@changeid>
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On Tue, 2020-08-25 at 19:36 +0800, Nicolas Boichat wrote:
> trace_printk is meant as a debugging tool, and should not be
> compiled into production code without specific debug Kconfig
> options enabled, or source code changes, as indicated by the
> warning that shows up on boot if any trace_printk is called:
>  **   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
>  **                                                      **
>  ** trace_printk() being used. Allocating extra memory.  **
>  **                                                      **
>  ** This means that this is a DEBUG kernel and it is     **
>  ** unsafe for production use.                           **
> 
> Let's warn developers when they try to submit such a change.
> 
> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>

thanks.

> ---
> See also extensive discussion under this thread:
> https://lkml.org/lkml/2020/8/20/244
> 
> This seems to be the simplest way to try to reduce the number
> of trace_printk that make it into the kernel.
> 
> Changes in v2:
>  - Use $1 directly, fix wording, remove final period.
> 
>  scripts/checkpatch.pl | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 4aa1d9d5e62c5b0..1102aa0ec2f7a05 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -4272,6 +4272,12 @@ sub process {
>  			     "Prefer dev_$level(... to dev_printk(KERN_$orig, ...\n" . $herecurr);
>  		}
>  
> +# trace_printk should not be used in production code.
> +		if ($line =~ /\b(trace_printk|trace_puts|ftrace_vprintk)\s*\(/) {
> +			WARN("TRACE_PRINTK",
> +			     "Do not use $1() in production code (this can be ignored if built only with a debug config option)\n" . $herecurr);
> +		}
> +
>  # ENOSYS means "bad syscall nr" and nothing else.  This will have a small
>  # number of false positives, but assembly files are not checked, so at
>  # least the arch entry code will not trigger this warning.