linux-kernel - [PATCH] firmware_loader: re-export fw_fallback_config into firmware

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Date:   Thu, 23 Apr 2020 20:31:40 +0000
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     gregkh@...uxfoundation.org
Cc:     akpm@...ux-foundation.org, josh@...htriplett.org,
        rishabhb@...eaurora.org, kubakici@...pl, maco@...roid.com,
        andy.gross@...aro.org, david.brown@...aro.org,
        bjorn.andersson@...aro.org, linux-wireless@...r.kernel.org,
        keescook@...omium.org, shuah@...nel.org, mfuzzey@...keon.com,
        zohar@...ux.vnet.ibm.com, dhowells@...hat.com,
        pali.rohar@...il.com, tiwai@...e.de, arend.vanspriel@...adcom.com,
        zajec5@...il.com, nbroeking@...com, markivx@...eaurora.org,
        broonie@...nel.org, dmitry.torokhov@...il.com, dwmw2@...radead.org,
        torvalds@...ux-foundation.org, Abhay_Salunke@...l.com,
        jewalt@...innovations.com, cantabile.desu@...il.com, ast@...com,
        andresx7@...il.com, dan.rue@...aro.org, brendanhiggins@...gle.com,
        yzaikin@...gle.com, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Luis Chamberlain <mcgrof@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Randy Dunlap <rdunlap@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: [PATCH] firmware_loader: re-export fw_fallback_config into firmware_loader's own namespace

From: Luis Chamberlain <mcgrof@...nel.org>

Christoph's recent patch "firmware_loader: remove unused exports", which
is not merged upstream yet, removed two exported symbols. One is fine to
remove since only built-in code uses it but the other is incorrect.

If CONFIG_FW_LOADER=m so the firmware_loader is modular but
CONFIG_FW_LOADER_USER_HELPER=y we fail at mostpost with:

ERROR: modpost: "fw_fallback_config" [drivers/base/firmware_loader/firmware_class.ko] undefined!

This happens because the variable fw_fallback_config is built into the
kernel if CONFIG_FW_LOADER_USER_HELPER=y always, so we need to grant
access to the firmware loader module by exporting it.

Instead of just exporting it as we used to, take advantage of the new
kernel symbol namespacing functionality, and export the symbol only to
the firmware loader private namespace. This would prevent misuses from
other drivers and makes it clear the goal is to keep this private to
the firmware loader alone.

Cc: Christoph Hellwig <hch@....de>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>
Fixes: "firmware_loader: remove unused exports"
Reported-by: Randy Dunlap <rdunlap@...radead.org>
Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---
 drivers/base/firmware_loader/fallback.c       | 3 +++
 drivers/base/firmware_loader/fallback_table.c | 1 +
 2 files changed, 4 insertions(+)

diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
index 1e9c96e3ed63..d9ac7296205e 100644
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -9,6 +9,7 @@
 #include <linux/umh.h>
 #include <linux/sysctl.h>
 #include <linux/vmalloc.h>
+#include <linux/module.h>
 
 #include "fallback.h"
 #include "firmware.h"
@@ -17,6 +18,8 @@
  * firmware fallback mechanism
  */
 
+MODULE_IMPORT_NS(FIRMWARE_LOADER_PRIVATE);
+
 extern struct firmware_fallback_config fw_fallback_config;
 
 /* These getters are vetted to use int properly */
diff --git a/drivers/base/firmware_loader/fallback_table.c b/drivers/base/firmware_loader/fallback_table.c
index 0a737349f78f..46a731dede6f 100644
--- a/drivers/base/firmware_loader/fallback_table.c
+++ b/drivers/base/firmware_loader/fallback_table.c
@@ -21,6 +21,7 @@ struct firmware_fallback_config fw_fallback_config = {
 	.loading_timeout = 60,
 	.old_timeout = 60,
 };
+EXPORT_SYMBOL_NS_GPL(fw_fallback_config, FIRMWARE_LOADER_PRIVATE);
 
 #ifdef CONFIG_SYSCTL
 struct ctl_table firmware_config_table[] = {
-- 
2.25.1