linux-kernel - Re: [PATCH -v2 6/7] module: Account for the build time module name mangling

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Message-ID: <20250502131547.GD4198@noisy.programming.kicks-ass.net>
Date: Fri, 2 May 2025 15:15:47 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: mcgrof@...nel.org
Cc: x86@...nel.org, hpa@...or.com, petr.pavlu@...e.com,
	samitolvanen@...gle.com, da.gomez@...sung.com, masahiroy@...nel.org,
	nathan@...nel.org, nicolas@...sle.eu, linux-kernel@...r.kernel.org,
	linux-modules@...r.kernel.org, linux-kbuild@...r.kernel.org,
	hch@...radead.org, gregkh@...uxfoundation.org,
	Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH -v2 6/7] module: Account for the build time module name
 mangling

On Mon, Dec 02, 2024 at 03:59:52PM +0100, Peter Zijlstra wrote:
> Sean noted that scripts/Makefile.lib:name-fix-token rule will mangle
> the module name with s/-/_/g.
> 
> Since this happens late in the build, only the kernel needs to bother
> with this, the modpost tool still sees the original name.
> 
> Reported-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/module/main.c |   26 +++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -1062,6 +1062,30 @@ static char *get_modinfo(const struct lo
>  }
>  
>  /*
> + * Like strncmp(), except s/-/_/g as per scripts/Makefile.lib:name-fix-token rule.
> + */
> +static int mod_strncmp(const char *str_a, const char *str_b, size_t n)
> +{
> +	for (int i = 0; i < n; i++) {
> +		char a = str_a[i];
> +		char b = str_b[i];
> +		int d;
> +
> +		if (a == '-') a = '_';
> +		if (b == '-') b = '_';
> +
> +		d = a - b;
> +		if (d)
> +			return d;
> +
> +		if (!a)
> +			break;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
>   * @namespace ~= "MODULE_foo-*,bar", match @modname to 'foo-*' or 'bar'
>   */
>  static bool verify_module_namespace(const char *namespace, const char *modname)
> @@ -1086,7 +1110,7 @@ static bool verify_module_namespace(cons
>  		if (*sep)
>  			sep++;
>  
> -		if (strncmp(namespace, modname, len) == 0 && (glob || len == modlen))
> +		if (mod_strncmp(namespace, modname, len) == 0 && (glob || len == modlen))
>  			return true;

Note that this is going to be a pain if we use glob_match(), because
then either all the patterns must already use '[-_]', or we need to
dynamically rewrite the glob.

Neither really appeals to me much.

Best to keep it simple.