queue-4.19/include-linux-bitrev.h-fix-constant-bitrev.patch

   1 From 6147e136ff5071609b54f18982dea87706288e21 Mon Sep 17 00:00:00 2001
   2 From: Arnd Bergmann <arnd@arndb.de>
   3 Date: Fri, 5 Apr 2019 18:38:53 -0700
   4 Subject: include/linux/bitrev.h: fix constant bitrev
   5
   6 From: Arnd Bergmann <arnd@arndb.de>
   7
   8 commit 6147e136ff5071609b54f18982dea87706288e21 upstream.
   9
  10 clang points out with hundreds of warnings that the bitrev macros have a
  11 problem with constant input:
  12
  13   drivers/hwmon/sht15.c:187:11: error: variable '__x' is uninitialized when used within its own initialization
  14         [-Werror,-Wuninitialized]
  15           u8 crc = bitrev8(data->val_status & 0x0F);
  16                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  17   include/linux/bitrev.h:102:21: note: expanded from macro 'bitrev8'
  18           __constant_bitrev8(__x) :                       \
  19           ~~~~~~~~~~~~~~~~~~~^~~~
  20   include/linux/bitrev.h:67:11: note: expanded from macro '__constant_bitrev8'
  21           u8 __x = x;                     \
  22              ~~~   ^
  23
  24 Both the bitrev and the __constant_bitrev macros use an internal
  25 variable named __x, which goes horribly wrong when passing one to the
  26 other.
  27
  28 The obvious fix is to rename one of the variables, so this adds an extra
  29 '_'.
  30
  31 It seems we got away with this because
  32
  33  - there are only a few drivers using bitrev macros
  34
  35  - usually there are no constant arguments to those
  36
  37  - when they are constant, they tend to be either 0 or (unsigned)-1
  38    (drivers/isdn/i4l/isdnhdlc.o, drivers/iio/amplifiers/ad8366.c) and
  39    give the correct result by pure chance.
  40
  41 In fact, the only driver that I could find that gets different results
  42 with this is drivers/net/wan/slic_ds26522.c, which in turn is a driver
  43 for fairly rare hardware (adding the maintainer to Cc for testing).
  44
  45 Link: http://lkml.kernel.org/r/20190322140503.123580-1-arnd@arndb.de
  46 Fixes: 556d2f055bf6 ("ARM: 8187/1: add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction")
  47 Signed-off-by: Arnd Bergmann <arnd@arndb.de>
  48 Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
  49 Cc: Zhao Qiang <qiang.zhao@nxp.com>
  50 Cc: Yalin Wang <yalin.wang@sonymobile.com>
  51 Cc: <stable@vger.kernel.org>
  52 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  53 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  54 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  55
  56 ---
  57  include/linux/bitrev.h |   46 +++++++++++++++++++++++-----------------------
  58  1 file changed, 23 insertions(+), 23 deletions(-)
  59
  60 --- a/include/linux/bitrev.h
  61 +++ b/include/linux/bitrev.h
  62 @@ -34,41 +34,41 @@ static inline u32 __bitrev32(u32 x)
  63
  64  #define __constant_bitrev32(x) \
  65  ({                                     \
  66 -       u32 __x = x;                    \
  67 -       __x = (__x >> 16) | (__x << 16);        \
  68 -       __x = ((__x & (u32)0xFF00FF00UL) >> 8) | ((__x & (u32)0x00FF00FFUL) << 8);      \
  69 -       __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4);      \
  70 -       __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2);      \
  71 -       __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1);      \
  72 -       __x;                                                            \
  73 +       u32 ___x = x;                   \
  74 +       ___x = (___x >> 16) | (___x << 16);     \
  75 +       ___x = ((___x & (u32)0xFF00FF00UL) >> 8) | ((___x & (u32)0x00FF00FFUL) << 8);   \
  76 +       ___x = ((___x & (u32)0xF0F0F0F0UL) >> 4) | ((___x & (u32)0x0F0F0F0FUL) << 4);   \
  77 +       ___x = ((___x & (u32)0xCCCCCCCCUL) >> 2) | ((___x & (u32)0x33333333UL) << 2);   \
  78 +       ___x = ((___x & (u32)0xAAAAAAAAUL) >> 1) | ((___x & (u32)0x55555555UL) << 1);   \
  79 +       ___x;                                                           \
  80  })
  81
  82  #define __constant_bitrev16(x) \
  83  ({                                     \
  84 -       u16 __x = x;                    \
  85 -       __x = (__x >> 8) | (__x << 8);  \
  86 -       __x = ((__x & (u16)0xF0F0U) >> 4) | ((__x & (u16)0x0F0FU) << 4);        \
  87 -       __x = ((__x & (u16)0xCCCCU) >> 2) | ((__x & (u16)0x3333U) << 2);        \
  88 -       __x = ((__x & (u16)0xAAAAU) >> 1) | ((__x & (u16)0x5555U) << 1);        \
  89 -       __x;                                                            \
  90 +       u16 ___x = x;                   \
  91 +       ___x = (___x >> 8) | (___x << 8);       \
  92 +       ___x = ((___x & (u16)0xF0F0U) >> 4) | ((___x & (u16)0x0F0FU) << 4);     \
  93 +       ___x = ((___x & (u16)0xCCCCU) >> 2) | ((___x & (u16)0x3333U) << 2);     \
  94 +       ___x = ((___x & (u16)0xAAAAU) >> 1) | ((___x & (u16)0x5555U) << 1);     \
  95 +       ___x;                                                           \
  96  })
  97
  98  #define __constant_bitrev8x4(x) \
  99  ({                     \
 100 -       u32 __x = x;    \
 101 -       __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4);      \
 102 -       __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2);      \
 103 -       __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1);      \
 104 -       __x;                                                            \
 105 +       u32 ___x = x;   \
 106 +       ___x = ((___x & (u32)0xF0F0F0F0UL) >> 4) | ((___x & (u32)0x0F0F0F0FUL) << 4);   \
 107 +       ___x = ((___x & (u32)0xCCCCCCCCUL) >> 2) | ((___x & (u32)0x33333333UL) << 2);   \
 108 +       ___x = ((___x & (u32)0xAAAAAAAAUL) >> 1) | ((___x & (u32)0x55555555UL) << 1);   \
 109 +       ___x;                                                           \
 110  })
 111
 112  #define __constant_bitrev8(x)  \
 113  ({                                     \
 114 -       u8 __x = x;                     \
 115 -       __x = (__x >> 4) | (__x << 4);  \
 116 -       __x = ((__x & (u8)0xCCU) >> 2) | ((__x & (u8)0x33U) << 2);      \
 117 -       __x = ((__x & (u8)0xAAU) >> 1) | ((__x & (u8)0x55U) << 1);      \
 118 -       __x;                                                            \
 119 +       u8 ___x = x;                    \
 120 +       ___x = (___x >> 4) | (___x << 4);       \
 121 +       ___x = ((___x & (u8)0xCCU) >> 2) | ((___x & (u8)0x33U) << 2);   \
 122 +       ___x = ((___x & (u8)0xAAU) >> 1) | ((___x & (u8)0x55U) << 1);   \
 123 +       ___x;                                                           \
 124  })
 125
 126  #define bitrev32(x) \