| Message ID | 20231127013511.26694-2-suhui@nfschina.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | bc8263083af60e7e57c6120edbc1f75d6c909a35 |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | [wireless-next,v3,1/2] wifi: rtlwifi: rtl8821ae: phy: remove some useless code | expand |
> -----Original Message----- > From: Su Hui <suhui@nfschina.com> > Sent: Monday, November 27, 2023 9:35 AM > To: Ping-Ke Shih <pkshih@realtek.com>; dan.carpenter@linaro.org; kvalo@kernel.org; nathan@kernel.org; > ndesaulniers@google.com; trix@redhat.com > Cc: Su Hui <suhui@nfschina.com>; lizetao1@huawei.com; linville@tuxdriver.com; Larry.Finger@lwfinger.net; > linux-wireless@vger.kernel.org; linux-kernel@vger.kernel.org; llvm@lists.linux.dev; > kernel-janitors@vger.kernel.org > Subject: [PATCH wireless-next v3 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior > > Clang staic checker warning: > drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c:184:49: > The result of the left shift is undefined due to shifting by '32', > which is greater or equal to the width of type 'u32'. > [core.UndefinedBinaryOperatorResult] > > If the value of the right operand is negative or is greater than or > equal to the width of the promoted left operand, the behavior is > undefined.[1][2] > > For example, when using different gcc's compilation optimizaation options > (-O0 or -O2), the result of '(u32)data << 32' is different. One is 0, the > other is old value of data. Let _rtl8821ae_phy_calculate_bit_shift()'s > return value less than 32 to fix this problem. Warn if bitmask is zero. > > [1]:https://stackoverflow.com/questions/11270492/what-does-the-c- > standard-say-about-bitshifting-more-bits-than-the-width-of-type > [2]:https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf > > Fixes: 21e4b0726dc6 ("rtlwifi: rtl8821ae: Move driver from staging to regular tree") > Signed-off-by: Su Hui <suhui@nfschina.com> Acked-by: Ping-Ke Shih <pkshih@realtek.com> > + if (WARN_ON_ONCE(!bitmask)) I test this patch with real hardware to connect 2GHz and 5GHz AP respectively and keep ping for a while. It doesn't throw warning by this statement.
diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c index 6df270e29e66..68c3fb0395ce 100644 --- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c @@ -29,9 +29,10 @@ static void _rtl8821ae_phy_rf_serial_write(struct ieee80211_hw *hw, u32 data); static u32 _rtl8821ae_phy_calculate_bit_shift(u32 bitmask) { - u32 i = ffs(bitmask); + if (WARN_ON_ONCE(!bitmask)) + return 0; - return i ? i - 1 : 32; + return __ffs(bitmask); } static bool _rtl8821ae_phy_bb8821a_config_parafile(struct ieee80211_hw *hw); /*static bool _rtl8812ae_phy_config_mac_with_headerfile(struct ieee80211_hw *hw);*/
Clang staic checker warning: drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c:184:49: The result of the left shift is undefined due to shifting by '32', which is greater or equal to the width of type 'u32'. [core.UndefinedBinaryOperatorResult] If the value of the right operand is negative or is greater than or equal to the width of the promoted left operand, the behavior is undefined.[1][2] For example, when using different gcc's compilation optimizaation options (-O0 or -O2), the result of '(u32)data << 32' is different. One is 0, the other is old value of data. Let _rtl8821ae_phy_calculate_bit_shift()'s return value less than 32 to fix this problem. Warn if bitmask is zero. [1]:https://stackoverflow.com/questions/11270492/what-does-the-c- standard-say-about-bitshifting-more-bits-than-the-width-of-type [2]:https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf Fixes: 21e4b0726dc6 ("rtlwifi: rtl8821ae: Move driver from staging to regular tree") Signed-off-by: Su Hui <suhui@nfschina.com> --- v3: - use __ffs() and make code briefer. (Thanks to Ping-Ke) v2: - fix the subject prefix problem - silence the warning by not return 32 bits rather than adding a type cast.(Thanks to Dan and Ping-Ke) drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)