+ mac80211-prevent-build-failure-with-config_ubsan=y.patch added to -mm tree

+ mac80211-prevent-build-failure-with-config_ubsan=y.patch added to -mm tree

[akpm]

The patch titled
     Subject: net/mac80211/debugfs.c: prevent build failure with CONFIG_UBSAN=y
has been added to the -mm tree.  Its filename is
     mac80211-prevent-build-failure-with-config_ubsan=y.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mac80211-prevent-build-failure-with-config_ubsan%3Dy.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mac80211-prevent-build-failure-with-config_ubsan%3Dy.patch

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------------------------------------------------------
From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Subject: net/mac80211/debugfs.c: prevent build failure with CONFIG_UBSAN=y

With upcoming CONFIG_UBSAN the following BUILD_BUG_ON in
net/mac80211/debugfs.c starts to trigger:
	BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1);

It seems, that compiler instrumentation causes some code deoptimizations.
Because of that GCC is not being able to resolve condition in BUILD_BUG_ON()
at compile time.

We could make size of hw_flag_names array unspecified and replace the
condition in BUILD_BUG_ON() with following:
	ARRAY_SIZE(hw_flag_names) != NUM_IEEE80211_HW_FLAGS

That will have the same effect as before (adding new flag without updating
array will trigger build failure) except it doesn't fail with CONFIG_UBSAN.
As a bonus this patch slightly decreases size of hw_flag_names array.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 net/mac80211/debugfs.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff -puN net/mac80211/debugfs.c~mac80211-prevent-build-failure-with-config_ubsan=y net/mac80211/debugfs.c
--- a/net/mac80211/debugfs.c~mac80211-prevent-build-failure-with-config_ubsan=y
+++ a/net/mac80211/debugfs.c
@@ -91,7 +91,7 @@ static const struct file_operations rese
 };
 #endif
 
-static const char *hw_flag_names[NUM_IEEE80211_HW_FLAGS + 1] = {
+static const char *hw_flag_names[] = {
 #define FLAG(F)	[IEEE80211_HW_##F] = #F
 	FLAG(HAS_RATE_CONTROL),
 	FLAG(RX_INCLUDES_FCS),
@@ -125,9 +125,6 @@ static const char *hw_flag_names[NUM_IEE
 	FLAG(TDLS_WIDER_BW),
 	FLAG(SUPPORTS_AMSDU_IN_AMPDU),
 	FLAG(BEACON_TX_STATUS),