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authorArnd Bergmann <arnd@arndb.de>2019-04-05 18:38:53 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-17 08:36:46 +0200
commita25d4ede3f6fc3b35da90c2ac22a5081c25a75d8 (patch)
tree77fb7a3901d5f0a1720f3a973fc488e537b2ca16
parenta957aa573c1e8c4e2bed1fa253b70ec6008fbde8 (diff)
include/linux/bitrev.h: fix constant bitrev
commit 6147e136ff5071609b54f18982dea87706288e21 upstream. clang points out with hundreds of warnings that the bitrev macros have a problem with constant input: drivers/hwmon/sht15.c:187:11: error: variable '__x' is uninitialized when used within its own initialization [-Werror,-Wuninitialized] u8 crc = bitrev8(data->val_status & 0x0F); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/bitrev.h:102:21: note: expanded from macro 'bitrev8' __constant_bitrev8(__x) : \ ~~~~~~~~~~~~~~~~~~~^~~~ include/linux/bitrev.h:67:11: note: expanded from macro '__constant_bitrev8' u8 __x = x; \ ~~~ ^ Both the bitrev and the __constant_bitrev macros use an internal variable named __x, which goes horribly wrong when passing one to the other. The obvious fix is to rename one of the variables, so this adds an extra '_'. It seems we got away with this because - there are only a few drivers using bitrev macros - usually there are no constant arguments to those - when they are constant, they tend to be either 0 or (unsigned)-1 (drivers/isdn/i4l/isdnhdlc.o, drivers/iio/amplifiers/ad8366.c) and give the correct result by pure chance. In fact, the only driver that I could find that gets different results with this is drivers/net/wan/slic_ds26522.c, which in turn is a driver for fairly rare hardware (adding the maintainer to Cc for testing). Link: http://lkml.kernel.org/r/20190322140503.123580-1-arnd@arndb.de Fixes: 556d2f055bf6 ("ARM: 8187/1: add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Cc: Zhao Qiang <qiang.zhao@nxp.com> Cc: Yalin Wang <yalin.wang@sonymobile.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--include/linux/bitrev.h36
1 files changed, 18 insertions, 18 deletions
diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
index fb790b8449c1..333e42cf08de 100644
--- a/include/linux/bitrev.h
+++ b/include/linux/bitrev.h
@@ -31,32 +31,32 @@ static inline u32 __bitrev32(u32 x)
#define __constant_bitrev32(x) \
({ \
- u32 __x = x; \
- __x = (__x >> 16) | (__x << 16); \
- __x = ((__x & (u32)0xFF00FF00UL) >> 8) | ((__x & (u32)0x00FF00FFUL) << 8); \
- __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4); \
- __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2); \
- __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1); \
- __x; \
+ u32 ___x = x; \
+ ___x = (___x >> 16) | (___x << 16); \
+ ___x = ((___x & (u32)0xFF00FF00UL) >> 8) | ((___x & (u32)0x00FF00FFUL) << 8); \
+ ___x = ((___x & (u32)0xF0F0F0F0UL) >> 4) | ((___x & (u32)0x0F0F0F0FUL) << 4); \
+ ___x = ((___x & (u32)0xCCCCCCCCUL) >> 2) | ((___x & (u32)0x33333333UL) << 2); \
+ ___x = ((___x & (u32)0xAAAAAAAAUL) >> 1) | ((___x & (u32)0x55555555UL) << 1); \
+ ___x; \
})
#define __constant_bitrev16(x) \
({ \
- u16 __x = x; \
- __x = (__x >> 8) | (__x << 8); \
- __x = ((__x & (u16)0xF0F0U) >> 4) | ((__x & (u16)0x0F0FU) << 4); \
- __x = ((__x & (u16)0xCCCCU) >> 2) | ((__x & (u16)0x3333U) << 2); \
- __x = ((__x & (u16)0xAAAAU) >> 1) | ((__x & (u16)0x5555U) << 1); \
- __x; \
+ u16 ___x = x; \
+ ___x = (___x >> 8) | (___x << 8); \
+ ___x = ((___x & (u16)0xF0F0U) >> 4) | ((___x & (u16)0x0F0FU) << 4); \
+ ___x = ((___x & (u16)0xCCCCU) >> 2) | ((___x & (u16)0x3333U) << 2); \
+ ___x = ((___x & (u16)0xAAAAU) >> 1) | ((___x & (u16)0x5555U) << 1); \
+ ___x; \
})
#define __constant_bitrev8(x) \
({ \
- u8 __x = x; \
- __x = (__x >> 4) | (__x << 4); \
- __x = ((__x & (u8)0xCCU) >> 2) | ((__x & (u8)0x33U) << 2); \
- __x = ((__x & (u8)0xAAU) >> 1) | ((__x & (u8)0x55U) << 1); \
- __x; \
+ u8 ___x = x; \
+ ___x = (___x >> 4) | (___x << 4); \
+ ___x = ((___x & (u8)0xCCU) >> 2) | ((___x & (u8)0x33U) << 2); \
+ ___x = ((___x & (u8)0xAAU) >> 1) | ((___x & (u8)0x55U) << 1); \
+ ___x; \
})
#define bitrev32(x) \