Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* bit search implementation
3 *
4 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 *
7 * Copyright (C) 2008 IBM Corporation
8 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
9 * (Inspired by David Howell's find_next_bit implementation)
10 *
11 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
12 * size and improve performance, 2015.
13 */
14
15#include <linux/bitops.h>
16#include <linux/bitmap.h>
17#include <linux/export.h>
18#include <linux/kernel.h>
19
20#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
21 !defined(find_next_bit_le) || !defined(find_next_zero_bit_le) || \
22 !defined(find_next_and_bit)
23/*
24 * This is a common helper function for find_next_bit, find_next_zero_bit, and
25 * find_next_and_bit. The differences are:
26 * - The "invert" argument, which is XORed with each fetched word before
27 * searching it for one bits.
28 * - The optional "addr2", which is anded with "addr1" if present.
29 */
30static unsigned long _find_next_bit(const unsigned long *addr1,
31 const unsigned long *addr2, unsigned long nbits,
32 unsigned long start, unsigned long invert, unsigned long le)
33{
34 unsigned long tmp, mask;
35
36 if (unlikely(start >= nbits))
37 return nbits;
38
39 tmp = addr1[start / BITS_PER_LONG];
40 if (addr2)
41 tmp &= addr2[start / BITS_PER_LONG];
42 tmp ^= invert;
43
44 /* Handle 1st word. */
45 mask = BITMAP_FIRST_WORD_MASK(start);
46 if (le)
47 mask = swab(mask);
48
49 tmp &= mask;
50
51 start = round_down(start, BITS_PER_LONG);
52
53 while (!tmp) {
54 start += BITS_PER_LONG;
55 if (start >= nbits)
56 return nbits;
57
58 tmp = addr1[start / BITS_PER_LONG];
59 if (addr2)
60 tmp &= addr2[start / BITS_PER_LONG];
61 tmp ^= invert;
62 }
63
64 if (le)
65 tmp = swab(tmp);
66
67 return min(start + __ffs(tmp), nbits);
68}
69#endif
70
71#ifndef find_next_bit
72/*
73 * Find the next set bit in a memory region.
74 */
75unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
76 unsigned long offset)
77{
78 return _find_next_bit(addr, NULL, size, offset, 0UL, 0);
79}
80EXPORT_SYMBOL(find_next_bit);
81#endif
82
83#ifndef find_next_zero_bit
84unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
85 unsigned long offset)
86{
87 return _find_next_bit(addr, NULL, size, offset, ~0UL, 0);
88}
89EXPORT_SYMBOL(find_next_zero_bit);
90#endif
91
92#if !defined(find_next_and_bit)
93unsigned long find_next_and_bit(const unsigned long *addr1,
94 const unsigned long *addr2, unsigned long size,
95 unsigned long offset)
96{
97 return _find_next_bit(addr1, addr2, size, offset, 0UL, 0);
98}
99EXPORT_SYMBOL(find_next_and_bit);
100#endif
101
102#ifndef find_first_bit
103/*
104 * Find the first set bit in a memory region.
105 */
106unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
107{
108 unsigned long idx;
109
110 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
111 if (addr[idx])
112 return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
113 }
114
115 return size;
116}
117EXPORT_SYMBOL(find_first_bit);
118#endif
119
120#ifndef find_first_zero_bit
121/*
122 * Find the first cleared bit in a memory region.
123 */
124unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
125{
126 unsigned long idx;
127
128 for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
129 if (addr[idx] != ~0UL)
130 return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
131 }
132
133 return size;
134}
135EXPORT_SYMBOL(find_first_zero_bit);
136#endif
137
138#ifndef find_last_bit
139unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
140{
141 if (size) {
142 unsigned long val = BITMAP_LAST_WORD_MASK(size);
143 unsigned long idx = (size-1) / BITS_PER_LONG;
144
145 do {
146 val &= addr[idx];
147 if (val)
148 return idx * BITS_PER_LONG + __fls(val);
149
150 val = ~0ul;
151 } while (idx--);
152 }
153 return size;
154}
155EXPORT_SYMBOL(find_last_bit);
156#endif
157
158#ifdef __BIG_ENDIAN
159
160#ifndef find_next_zero_bit_le
161unsigned long find_next_zero_bit_le(const void *addr, unsigned
162 long size, unsigned long offset)
163{
164 return _find_next_bit(addr, NULL, size, offset, ~0UL, 1);
165}
166EXPORT_SYMBOL(find_next_zero_bit_le);
167#endif
168
169#ifndef find_next_bit_le
170unsigned long find_next_bit_le(const void *addr, unsigned
171 long size, unsigned long offset)
172{
173 return _find_next_bit(addr, NULL, size, offset, 0UL, 1);
174}
175EXPORT_SYMBOL(find_next_bit_le);
176#endif
177
178#endif /* __BIG_ENDIAN */
179
180unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
181 unsigned long size, unsigned long offset)
182{
183 offset = find_next_bit(addr, size, offset);
184 if (offset == size)
185 return size;
186
187 offset = round_down(offset, 8);
188 *clump = bitmap_get_value8(addr, offset);
189
190 return offset;
191}
192EXPORT_SYMBOL(find_next_clump8);