linux-kernel - [PATCH] wireless: wext: avoid gcc -O3 warning

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Date:   Tue,  7 Jan 2020 21:07:35 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Johannes Berg <johannes@...solutions.net>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Oleksandr Natalenko <oleksandr@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] wireless: wext: avoid gcc -O3 warning

After the introduction of CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3,
the wext code produces a bogus warning:

In function 'iw_handler_get_iwstats',
    inlined from 'ioctl_standard_call' at net/wireless/wext-core.c:1015:9,
    inlined from 'wireless_process_ioctl' at net/wireless/wext-core.c:935:10,
    inlined from 'wext_ioctl_dispatch.part.8' at net/wireless/wext-core.c:986:8,
    inlined from 'wext_handle_ioctl':
net/wireless/wext-core.c:671:3: error: argument 1 null where non-null expected [-Werror=nonnull]
   memcpy(extra, stats, sizeof(struct iw_statistics));
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from arch/x86/include/asm/string.h:5,
net/wireless/wext-core.c: In function 'wext_handle_ioctl':
arch/x86/include/asm/string_64.h:14:14: note: in a call to function 'memcpy' declared here

The problem is that ioctl_standard_call() sometimes calls the handler
with a NULL argument that would cause a problem for iw_handler_get_iwstats.
However, iw_handler_get_iwstats never actually gets called that way.

Marking that function as noinline avoids the warning and leads
to slightly smaller object code as well.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 net/wireless/wext-core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c
index 5e677dac2a0c..69102fda9ebd 100644
--- a/net/wireless/wext-core.c
+++ b/net/wireless/wext-core.c
@@ -657,7 +657,8 @@ struct iw_statistics *get_wireless_stats(struct net_device *dev)
 	return NULL;
 }
 
-static int iw_handler_get_iwstats(struct net_device *		dev,
+/* noinline to avoid a bogus warning with -O3 */
+static noinline int iw_handler_get_iwstats(struct net_device *	dev,
 				  struct iw_request_info *	info,
 				  union iwreq_data *		wrqu,
 				  char *			extra)
-- 
2.20.0