tools: Copy bitfield.h from the kernel sources

Copy bitfield.h from include/linux/bitfield.h.  A subsequent change will
make use of some FIELD_{GET,PREP} macros defined in this header.

The header was copied as-is, no changes needed.

Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221017195834.2295901-6-ricarkol@google.com

diff --git a/tools/include/linux/bitfield.h b/tools/include/linux/bitfield.h
new file mode 100644 (file)
index 0000000..6093fa6
--- /dev/null
+++ b/tools/include/linux/bitfield.h
@@ -0,0 +1,176 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name>
+ * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
+ */
+
+#ifndef _LINUX_BITFIELD_H
+#define _LINUX_BITFIELD_H
+
+#include <linux/build_bug.h>
+#include <asm/byteorder.h>
+
+/*
+ * Bitfield access macros
+ *
+ * FIELD_{GET,PREP} macros take as first parameter shifted mask
+ * from which they extract the base mask and shift amount.
+ * Mask must be a compilation time constant.
+ *
+ * Example:
+ *
+ *  #define REG_FIELD_A  GENMASK(6, 0)
+ *  #define REG_FIELD_B  BIT(7)
+ *  #define REG_FIELD_C  GENMASK(15, 8)
+ *  #define REG_FIELD_D  GENMASK(31, 16)
+ *
+ * Get:
+ *  a = FIELD_GET(REG_FIELD_A, reg);
+ *  b = FIELD_GET(REG_FIELD_B, reg);
+ *
+ * Set:
+ *  reg = FIELD_PREP(REG_FIELD_A, 1) |
+ *       FIELD_PREP(REG_FIELD_B, 0) |
+ *       FIELD_PREP(REG_FIELD_C, c) |
+ *       FIELD_PREP(REG_FIELD_D, 0x40);
+ *
+ * Modify:
+ *  reg &= ~REG_FIELD_C;
+ *  reg |= FIELD_PREP(REG_FIELD_C, c);
+ */
+
+#define __bf_shf(x) (__builtin_ffsll(x) - 1)
+
+#define __scalar_type_to_unsigned_cases(type)                          \
+               unsigned type:  (unsigned type)0,                       \
+               signed type:    (unsigned type)0
+
+#define __unsigned_scalar_typeof(x) typeof(                            \
+               _Generic((x),                                           \
+                       char:   (unsigned char)0,                       \
+                       __scalar_type_to_unsigned_cases(char),          \
+                       __scalar_type_to_unsigned_cases(short),         \
+                       __scalar_type_to_unsigned_cases(int),           \
+                       __scalar_type_to_unsigned_cases(long),          \
+                       __scalar_type_to_unsigned_cases(long long),     \
+                       default: (x)))
+
+#define __bf_cast_unsigned(type, x)    ((__unsigned_scalar_typeof(type))(x))
+
+#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx)                      \
+       ({                                                              \
+               BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),          \
+                                _pfx "mask is not constant");          \
+               BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero");    \
+               BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?           \
+                                ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
+                                _pfx "value too large for the field"); \
+               BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >     \
+                                __bf_cast_unsigned(_reg, ~0ull),       \
+                                _pfx "type of reg too small for mask"); \
+               __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +                 \
+                                             (1ULL << __bf_shf(_mask))); \
+       })
+
+/**
+ * FIELD_MAX() - produce the maximum value representable by a field
+ * @_mask: shifted mask defining the field's length and position
+ *
+ * FIELD_MAX() returns the maximum value that can be held in the field
+ * specified by @_mask.
+ */
+#define FIELD_MAX(_mask)                                               \
+       ({                                                              \
+               __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: ");     \
+               (typeof(_mask))((_mask) >> __bf_shf(_mask));            \
+       })
+
+/**
+ * FIELD_FIT() - check if value fits in the field
+ * @_mask: shifted mask defining the field's length and position
+ * @_val:  value to test against the field
+ *
+ * Return: true if @_val can fit inside @_mask, false if @_val is too big.
+ */
+#define FIELD_FIT(_mask, _val)                                         \
+       ({                                                              \
+               __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: ");     \
+               !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
+       })
+
+/**
+ * FIELD_PREP() - prepare a bitfield element
+ * @_mask: shifted mask defining the field's length and position
+ * @_val:  value to put in the field
+ *
+ * FIELD_PREP() masks and shifts up the value.  The result should
+ * be combined with other fields of the bitfield using logical OR.
+ */
+#define FIELD_PREP(_mask, _val)                                                \
+       ({                                                              \
+               __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");    \
+               ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask);   \
+       })
+
+/**
+ * FIELD_GET() - extract a bitfield element
+ * @_mask: shifted mask defining the field's length and position
+ * @_reg:  value of entire bitfield
+ *
+ * FIELD_GET() extracts the field specified by @_mask from the
+ * bitfield passed in as @_reg by masking and shifting it down.
+ */
+#define FIELD_GET(_mask, _reg)                                         \
+       ({                                                              \
+               __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: ");       \
+               (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
+       })
+
+extern void __compiletime_error("value doesn't fit into mask")
+__field_overflow(void);
+extern void __compiletime_error("bad bitfield mask")
+__bad_mask(void);
+static __always_inline u64 field_multiplier(u64 field)
+{
+       if ((field | (field - 1)) & ((field | (field - 1)) + 1))
+               __bad_mask();
+       return field & -field;
+}
+static __always_inline u64 field_mask(u64 field)
+{
+       return field / field_multiplier(field);
+}
+#define field_max(field)       ((typeof(field))field_mask(field))
+#define ____MAKE_OP(type,base,to,from)                                 \
+static __always_inline __##type type##_encode_bits(base v, base field) \
+{                                                                      \
+       if (__builtin_constant_p(v) && (v & ~field_mask(field)))        \
+               __field_overflow();                                     \
+       return to((v & field_mask(field)) * field_multiplier(field));   \
+}                                                                      \
+static __always_inline __##type type##_replace_bits(__##type old,      \
+                                       base val, base field)           \
+{                                                                      \
+       return (old & ~to(field)) | type##_encode_bits(val, field);     \
+}                                                                      \
+static __always_inline void type##p_replace_bits(__##type *p,          \
+                                       base val, base field)           \
+{                                                                      \
+       *p = (*p & ~to(field)) | type##_encode_bits(val, field);        \
+}                                                                      \
+static __always_inline base type##_get_bits(__##type v, base field)    \
+{                                                                      \
+       return (from(v) & field)/field_multiplier(field);               \
+}
+#define __MAKE_OP(size)                                                        \
+       ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
+       ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
+       ____MAKE_OP(u##size,u##size,,)
+____MAKE_OP(u8,u8,,)
+__MAKE_OP(16)
+__MAKE_OP(32)
+__MAKE_OP(64)
+#undef __MAKE_OP
+#undef ____MAKE_OP
+
+#endif