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@xxxxxxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
---
net/mac80211/debugfs.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index abbdff0..3e24d0d 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -91,7 +91,7 @@ static const struct file_operations reset_ops = {
};
#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),
@@ -126,9 +126,6 @@ static const char *hw_flag_names[NUM_IEEE80211_HW_FLAGS + 1] = {
FLAG(SUPPORTS_AMSDU_IN_AMPDU),
FLAG(BEACON_TX_STATUS),
FLAG(NEEDS_UNIQUE_STA_ADDR),
-
- /* keep last for the build bug below */
- (void *)0x1
#undef FLAG
};
@@ -148,7 +145,7 @@ static ssize_t hwflags_read(struct file *file, char __user *user_buf,
/* fail compilation if somebody adds or removes
* a flag without updating the name array above
*/
- BUILD_BUG_ON(hw_flag_names[NUM_IEEE80211_HW_FLAGS] != (void *)0x1);
+ BUILD_BUG_ON(ARRAY_SIZE(hw_flag_names) != NUM_IEEE80211_HW_FLAGS);
for (i = 0; i < NUM_IEEE80211_HW_FLAGS; i++) {
if (test_bit(i, local->hw.flags))
--
2.4.10
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