linux-kernel - Re: [PATCH] checkpatch: add new warning when lookup_symbol

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Date:   Thu, 17 Dec 2020 09:27:27 -0800
From:   Joe Perches <joe@...ches.com>
To:     Helge Deller <deller@....de>, Andy Whitcroft <apw@...onical.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] checkpatch: add new warning when lookup_symbol_name()
 is used

On Thu, 2020-12-17 at 18:11 +0100, Helge Deller wrote:
> In most cases people use lookup_symbol_name() to resolve a kernel symbol
> and then print it via printk().
> 
> In such cases using the %ps, %pS, %pSR or %pB printk formats are easier
> to use and thus should be preferred.
[]
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -4317,6 +4317,12 @@ sub process {
>  			     "LINUX_VERSION_CODE should be avoided, code should be for the version to which it is merged\n" . $herecurr);
>  		}
> 
> +# avoid lookup_symbol_name()
> +		if ($line =~ /\blookup_symbol_name\b/) {
> +			WARN("PREFER_PRINTK_FORMAT",
> +			     "If possible prefer %ps or %pS printk format string to print symbol name instead of using lookup_symbol_name()\n" . $herecurr);
> +		}
> +
>  # check for uses of printk_ratelimit
>  		if ($line =~ /\bprintk_ratelimit\s*\(/) {
>  			WARN("PRINTK_RATELIMITED",

Huh?  nak.

lookup_symbol_name is used in the kernel a grand total of 3 times.
2 uses are kprobe, the other is fs/proc

None of the existing uses is equivalent to %ps

Why should this be applied?