Re: [PATCH] module.h: allow #define strings to work with MODULE_IMPORT_NS

From: Matthias Maennich
Date: Mon Jan 10 2022 - 12:39:41 EST


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@xxxxxxxxxx>
Cc: Jessica Yu <jeyu@xxxxxxxxxx>
Cc: Matthias Maennich <maennich@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

Reviewed-by: Matthias Maennich <maennich@xxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxx/

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