tools/include/linux/bits.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_BITS_H
   3 #define __LINUX_BITS_H
   4
   5 #include <linux/const.h>
   6 #include <vdso/bits.h>
   7 #include <uapi/linux/bits.h>
   8 #include <asm/bitsperlong.h>
   9
  10 #define BIT_MASK(nr)            (UL(1) << ((nr) % BITS_PER_LONG))
  11 #define BIT_WORD(nr)            ((nr) / BITS_PER_LONG)
  12 #define BIT_ULL_MASK(nr)        (ULL(1) << ((nr) % BITS_PER_LONG_LONG))
  13 #define BIT_ULL_WORD(nr)        ((nr) / BITS_PER_LONG_LONG)
  14 #define BITS_PER_BYTE           8
  15 #define BITS_PER_TYPE(type)     (sizeof(type) * BITS_PER_BYTE)
  16
  17 /*
  18  * Create a contiguous bitmask starting at bit position @l and ending at
  19  * position @h. For example
  20  * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
  21  */
  22 #if !defined(__ASSEMBLY__)
  23
  24 /*
  25  * Missing asm support
  26  *
  27  * GENMASK_U*() and BIT_U*() depend on BITS_PER_TYPE() which relies on sizeof(),
  28  * something not available in asm. Nevertheless, fixed width integers is a C
  29  * concept. Assembly code can rely on the long and long long versions instead.
  30  */
  31
  32 #include <linux/build_bug.h>
  33 #include <linux/compiler.h>
  34 #include <linux/overflow.h>
  35
  36 #define GENMASK_INPUT_CHECK(h, l) BUILD_BUG_ON_ZERO(const_true((l) > (h)))
  37
  38 /*
  39  * Generate a mask for the specified type @t. Additional checks are made to
  40  * guarantee the value returned fits in that type, relying on
  41  * -Wshift-count-overflow compiler check to detect incompatible arguments.
  42  * For example, all these create build errors or warnings:
  43  *
  44  * - GENMASK(15, 20): wrong argument order
  45  * - GENMASK(72, 15): doesn't fit unsigned long
  46  * - GENMASK_U32(33, 15): doesn't fit in a u32
  47  */
  48 #define GENMASK_TYPE(t, h, l)                                   \
  49         ((t)(GENMASK_INPUT_CHECK(h, l) +                        \
  50              (type_max(t) << (l) &                              \
  51               type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
  52
  53 #define GENMASK_U8(h, l)        GENMASK_TYPE(u8, h, l)
  54 #define GENMASK_U16(h, l)       GENMASK_TYPE(u16, h, l)
  55 #define GENMASK_U32(h, l)       GENMASK_TYPE(u32, h, l)
  56 #define GENMASK_U64(h, l)       GENMASK_TYPE(u64, h, l)
  57
  58 /*
  59  * Fixed-type variants of BIT(), with additional checks like GENMASK_TYPE(). The
  60  * following examples generate compiler warnings due to -Wshift-count-overflow:
  61  *
  62  * - BIT_U8(8)
  63  * - BIT_U32(-1)
  64  * - BIT_U32(40)
  65  */
  66 #define BIT_INPUT_CHECK(type, nr) \
  67         BUILD_BUG_ON_ZERO(const_true((nr) >= BITS_PER_TYPE(type)))
  68
  69 #define BIT_TYPE(type, nr) ((type)(BIT_INPUT_CHECK(type, nr) + BIT_ULL(nr)))
  70
  71 #define BIT_U8(nr)      BIT_TYPE(u8, nr)
  72 #define BIT_U16(nr)     BIT_TYPE(u16, nr)
  73 #define BIT_U32(nr)     BIT_TYPE(u32, nr)
  74 #define BIT_U64(nr)     BIT_TYPE(u64, nr)
  75
  76 #else /* defined(__ASSEMBLY__) */
  77
  78 /*
  79  * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
  80  * disable the input check if that is the case.
  81  */
  82 #define GENMASK_INPUT_CHECK(h, l) 0
  83
  84 #endif /* !defined(__ASSEMBLY__) */
  85
  86 #define GENMASK(h, l) \
  87         (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
  88 #define GENMASK_ULL(h, l) \
  89         (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
  90
  91 #if !defined(__ASSEMBLY__)
  92 /*
  93  * Missing asm support
  94  *
  95  * __GENMASK_U128() depends on _BIT128() which would not work
  96  * in the asm code, as it shifts an 'unsigned __int128' data
  97  * type instead of direct representation of 128 bit constants
  98  * such as long and unsigned long. The fundamental problem is
  99  * that a 128 bit constant will get silently truncated by the
 100  * gcc compiler.
 101  */
 102 #define GENMASK_U128(h, l) \
 103         (GENMASK_INPUT_CHECK(h, l) + __GENMASK_U128(h, l))
 104 #endif
 105
 106 #endif  /* __LINUX_BITS_H */