Linux kernel mirror (for testing)
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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 */