bits.h

 1/* SPDX-License-Identifier: GPL-2.0 */
 2#ifndef __LINUX_BITS_H
 3#define __LINUX_BITS_H
 4
 5#include <vdso/bits.h>
 6#include <uapi/linux/bits.h>
 7
 8#define BIT_MASK(nr)		(UL(1) << ((nr) % BITS_PER_LONG))
 9#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
10#define BIT_ULL_MASK(nr)	(ULL(1) << ((nr) % BITS_PER_LONG_LONG))
11#define BIT_ULL_WORD(nr)	((nr) / BITS_PER_LONG_LONG)
12#define BITS_PER_BYTE		8
13#define BITS_PER_TYPE(type)	(sizeof(type) * BITS_PER_BYTE)
14
15/*
16 * Create a contiguous bitmask starting at bit position @l and ending at
17 * position @h. For example
18 * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
19 */
20#if !defined(__ASSEMBLY__)
21
22/*
23 * Missing asm support
24 *
25 * GENMASK_U*() and BIT_U*() depend on BITS_PER_TYPE() which relies on sizeof(),
26 * something not available in asm. Nevertheless, fixed width integers is a C
27 * concept. Assembly code can rely on the long and long long versions instead.
28 */
29
30#include <linux/build_bug.h>
31#include <linux/compiler.h>
32#include <linux/overflow.h>
33
34#define GENMASK_INPUT_CHECK(h, l) BUILD_BUG_ON_ZERO(const_true((l) > (h)))
35
36/*
37 * Generate a mask for the specified type @t. Additional checks are made to
38 * guarantee the value returned fits in that type, relying on
39 * -Wshift-count-overflow compiler check to detect incompatible arguments.
40 * For example, all these create build errors or warnings:
41 *
42 * - GENMASK(15, 20): wrong argument order
43 * - GENMASK(72, 15): doesn't fit unsigned long
44 * - GENMASK_U32(33, 15): doesn't fit in a u32
45 */
46#define GENMASK_TYPE(t, h, l)					\
47	((t)(GENMASK_INPUT_CHECK(h, l) +			\
48	     (type_max(t) << (l) &				\
49	      type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
50
51#define GENMASK(h, l)		GENMASK_TYPE(unsigned long, h, l)
52#define GENMASK_ULL(h, l)	GENMASK_TYPE(unsigned long long, h, l)
53
54#define GENMASK_U8(h, l)	GENMASK_TYPE(u8, h, l)
55#define GENMASK_U16(h, l)	GENMASK_TYPE(u16, h, l)
56#define GENMASK_U32(h, l)	GENMASK_TYPE(u32, h, l)
57#define GENMASK_U64(h, l)	GENMASK_TYPE(u64, h, l)
58#define GENMASK_U128(h, l)	GENMASK_TYPE(u128, h, l)
59
60/*
61 * Fixed-type variants of BIT(), with additional checks like GENMASK_TYPE(). The
62 * following examples generate compiler warnings due to -Wshift-count-overflow:
63 *
64 * - BIT_U8(8)
65 * - BIT_U32(-1)
66 * - BIT_U32(40)
67 */
68#define BIT_INPUT_CHECK(type, nr) \
69	BUILD_BUG_ON_ZERO(const_true((nr) >= BITS_PER_TYPE(type)))
70
71#define BIT_TYPE(type, nr) ((type)(BIT_INPUT_CHECK(type, nr) + BIT_ULL(nr)))
72
73#define BIT_U8(nr)	BIT_TYPE(u8, nr)
74#define BIT_U16(nr)	BIT_TYPE(u16, nr)
75#define BIT_U32(nr)	BIT_TYPE(u32, nr)
76#define BIT_U64(nr)	BIT_TYPE(u64, nr)
77
78#else /* defined(__ASSEMBLY__) */
79
80/*
81 * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
82 * disable the input check if that is the case.
83 */
84#define GENMASK(h, l)		__GENMASK(h, l)
85#define GENMASK_ULL(h, l)	__GENMASK_ULL(h, l)
86
87#endif /* !defined(__ASSEMBLY__) */
88
89#endif	/* __LINUX_BITS_H */