linux-kernel - Re: [PATCH] checkpatch: Warn if trace

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Message-ID: <6972ee8f4bd9d19c137e2526fae53cf4379f4499.camel@perches.com>
Date:   Tue, 25 Aug 2020 00:23:26 -0700
From:   Joe Perches <joe@...ches.com>
To:     Nicolas Boichat <drinkcat@...omium.org>,
        Andy Whitcroft <apw@...onical.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] checkpatch: Warn if trace_printk and friends are called

On Tue, 2020-08-25 at 15:09 +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@...omium.org>
> ---
> 
> 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.

I don't have a real objection, just some nits.

> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -4272,6 +4272,14 @@ 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*\(/) {
> +			my $func = $1;
> +
> +			WARN("TRACE_PRINTK",
> +			     "Do not use $func() in production code (this can be ignored if built only behind a debug config option).\n" . $herecurr);

You don't need to do an assign, you could use $1 directly.
I think 'built only behind' could be "building only with'.
No periods before the newline either.

> +		}
> +
>  # 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.