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6147e136ff
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: 556d2f055b ("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>
105 lines
2.5 KiB
C
105 lines
2.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_BITREV_H
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#define _LINUX_BITREV_H
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#include <linux/types.h>
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#ifdef CONFIG_HAVE_ARCH_BITREVERSE
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#include <asm/bitrev.h>
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#define __bitrev32 __arch_bitrev32
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#define __bitrev16 __arch_bitrev16
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#define __bitrev8 __arch_bitrev8
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#else
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extern u8 const byte_rev_table[256];
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static inline u8 __bitrev8(u8 byte)
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{
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return byte_rev_table[byte];
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}
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static inline u16 __bitrev16(u16 x)
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{
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return (__bitrev8(x & 0xff) << 8) | __bitrev8(x >> 8);
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}
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static inline u32 __bitrev32(u32 x)
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{
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return (__bitrev16(x & 0xffff) << 16) | __bitrev16(x >> 16);
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}
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#endif /* CONFIG_HAVE_ARCH_BITREVERSE */
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#define __bitrev8x4(x) (__bitrev32(swab32(x)))
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#define __constant_bitrev32(x) \
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({ \
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u32 ___x = x; \
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___x = (___x >> 16) | (___x << 16); \
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___x = ((___x & (u32)0xFF00FF00UL) >> 8) | ((___x & (u32)0x00FF00FFUL) << 8); \
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___x = ((___x & (u32)0xF0F0F0F0UL) >> 4) | ((___x & (u32)0x0F0F0F0FUL) << 4); \
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___x = ((___x & (u32)0xCCCCCCCCUL) >> 2) | ((___x & (u32)0x33333333UL) << 2); \
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___x = ((___x & (u32)0xAAAAAAAAUL) >> 1) | ((___x & (u32)0x55555555UL) << 1); \
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___x; \
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})
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#define __constant_bitrev16(x) \
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({ \
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u16 ___x = x; \
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___x = (___x >> 8) | (___x << 8); \
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___x = ((___x & (u16)0xF0F0U) >> 4) | ((___x & (u16)0x0F0FU) << 4); \
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___x = ((___x & (u16)0xCCCCU) >> 2) | ((___x & (u16)0x3333U) << 2); \
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___x = ((___x & (u16)0xAAAAU) >> 1) | ((___x & (u16)0x5555U) << 1); \
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___x; \
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})
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#define __constant_bitrev8x4(x) \
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({ \
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u32 ___x = x; \
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___x = ((___x & (u32)0xF0F0F0F0UL) >> 4) | ((___x & (u32)0x0F0F0F0FUL) << 4); \
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___x = ((___x & (u32)0xCCCCCCCCUL) >> 2) | ((___x & (u32)0x33333333UL) << 2); \
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___x = ((___x & (u32)0xAAAAAAAAUL) >> 1) | ((___x & (u32)0x55555555UL) << 1); \
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___x; \
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})
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#define __constant_bitrev8(x) \
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({ \
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u8 ___x = x; \
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___x = (___x >> 4) | (___x << 4); \
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___x = ((___x & (u8)0xCCU) >> 2) | ((___x & (u8)0x33U) << 2); \
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___x = ((___x & (u8)0xAAU) >> 1) | ((___x & (u8)0x55U) << 1); \
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___x; \
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})
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#define bitrev32(x) \
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({ \
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u32 __x = x; \
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__builtin_constant_p(__x) ? \
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__constant_bitrev32(__x) : \
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__bitrev32(__x); \
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})
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#define bitrev16(x) \
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({ \
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u16 __x = x; \
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__builtin_constant_p(__x) ? \
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__constant_bitrev16(__x) : \
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__bitrev16(__x); \
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})
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#define bitrev8x4(x) \
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({ \
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u32 __x = x; \
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__builtin_constant_p(__x) ? \
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__constant_bitrev8x4(__x) : \
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__bitrev8x4(__x); \
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})
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#define bitrev8(x) \
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({ \
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u8 __x = x; \
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__builtin_constant_p(__x) ? \
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__constant_bitrev8(__x) : \
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__bitrev8(__x) ; \
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})
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#endif /* _LINUX_BITREV_H */
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