linux-kernel - Re: [PATCH] module.h: allow #define strings to work with MODULE_IMPORT

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Message-ID: <YdxvUYRejf2K6YJq@google.com>
Date:   Mon, 10 Jan 2022 17:39:29 +0000
From:   Matthias Maennich <maennich@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, Luis Chamberlain <mcgrof@...nel.org>,
        Jessica Yu <jeyu@...nel.org>
Subject: Re: [PATCH] module.h: allow #define strings to work with
 MODULE_IMPORT_NS

On Sat, Jan 08, 2022 at 03:06:57PM +0100, Greg Kroah-Hartman wrote:
>The MODULE_IMPORT_NS() macro does not allow defined strings to work
>properly with it, so add a layer of indirection to allow this to happen.
>
>Cc: Luis Chamberlain <mcgrof@...nel.org>
>Cc: Jessica Yu <jeyu@...nel.org>
>Cc: Matthias Maennich <maennich@...gle.com>
>Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

Reviewed-by: Matthias Maennich <maennich@...gle.com>

Cheers,
Matthias

>---
>Note, there is no in-kernel user of this, I wrote this to help deal with
>some module namespace issues that Android kernels were having where we
>wanted to put the namespace name in a build #define to make things
>easier over time when combined with the change at:
>	https://lore.kernel.org/all/20220108140415.3360088-1-gregkh@linuxfoundation.org/
>
>I can also see this be used in ways to make namespace names up "on the
>fly at build time" when combined with the above-referenced change to
>create a different namespace for every time the kernel is built to do a
>poor-man's symbol mangling to make life harder for out-of-tree modules.
>Not that I would ever suggest such a thing :)
>
> include/linux/module.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/include/linux/module.h b/include/linux/module.h
>index c9f1200b2312..f4338235ed2c 100644
>--- a/include/linux/module.h
>+++ b/include/linux/module.h
>@@ -290,7 +290,8 @@ extern typeof(name) __mod_##type##__##name##_device_table		\
>  * files require multiple MODULE_FIRMWARE() specifiers */
> #define MODULE_FIRMWARE(_firmware) MODULE_INFO(firmware, _firmware)
>
>-#define MODULE_IMPORT_NS(ns) MODULE_INFO(import_ns, #ns)
>+#define _MODULE_IMPORT_NS(ns)	MODULE_INFO(import_ns, #ns)
>+#define MODULE_IMPORT_NS(ns)	_MODULE_IMPORT_NS(ns)
>
> struct notifier_block;
>
>-- 
>2.34.1
>