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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/math.h>
19#include <linux/minmax.h>
20#include <linux/swab.h>
21
22/*
23 * Common helper for find_bit() function family
24 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
25 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
26 * @size: The bitmap size in bits
27 */
28#define FIND_FIRST_BIT(FETCH, MUNGE, size) \
29({ \
30 unsigned long idx, val, sz = (size); \
31 \
32 for (idx = 0; idx * BITS_PER_LONG < sz; idx++) { \
33 val = (FETCH); \
34 if (val) { \
35 sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz); \
36 break; \
37 } \
38 } \
39 \
40 sz; \
41})
42
43/*
44 * Common helper for find_next_bit() function family
45 * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
46 * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
47 * @size: The bitmap size in bits
48 * @start: The bitnumber to start searching at
49 */
50#define FIND_NEXT_BIT(FETCH, MUNGE, size, start) \
51({ \
52 unsigned long mask, idx, tmp, sz = (size), __start = (start); \
53 \
54 if (unlikely(__start >= sz)) \
55 goto out; \
56 \
57 mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start)); \
58 idx = __start / BITS_PER_LONG; \
59 \
60 for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) { \
61 if ((idx + 1) * BITS_PER_LONG >= sz) \
62 goto out; \
63 idx++; \
64 } \
65 \
66 sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz); \
67out: \
68 sz; \
69})
70
71#define FIND_NTH_BIT(FETCH, size, num) \
72({ \
73 unsigned long sz = (size), nr = (num), idx, w, tmp; \
74 \
75 for (idx = 0; (idx + 1) * BITS_PER_LONG <= sz; idx++) { \
76 if (idx * BITS_PER_LONG + nr >= sz) \
77 goto out; \
78 \
79 tmp = (FETCH); \
80 w = hweight_long(tmp); \
81 if (w > nr) \
82 goto found; \
83 \
84 nr -= w; \
85 } \
86 \
87 if (sz % BITS_PER_LONG) \
88 tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz); \
89found: \
90 sz = min(idx * BITS_PER_LONG + fns(tmp, nr), sz); \
91out: \
92 sz; \
93})
94
95#ifndef find_first_bit
96/*
97 * Find the first set bit in a memory region.
98 */
99unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
100{
101 return FIND_FIRST_BIT(addr[idx], /* nop */, size);
102}
103EXPORT_SYMBOL(_find_first_bit);
104#endif
105
106#ifndef find_first_and_bit
107/*
108 * Find the first set bit in two memory regions.
109 */
110unsigned long _find_first_and_bit(const unsigned long *addr1,
111 const unsigned long *addr2,
112 unsigned long size)
113{
114 return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size);
115}
116EXPORT_SYMBOL(_find_first_and_bit);
117#endif
118
119#ifndef find_first_zero_bit
120/*
121 * Find the first cleared bit in a memory region.
122 */
123unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
124{
125 return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
126}
127EXPORT_SYMBOL(_find_first_zero_bit);
128#endif
129
130#ifndef find_next_bit
131unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
132{
133 return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
134}
135EXPORT_SYMBOL(_find_next_bit);
136#endif
137
138unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n)
139{
140 return FIND_NTH_BIT(addr[idx], size, n);
141}
142EXPORT_SYMBOL(__find_nth_bit);
143
144unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2,
145 unsigned long size, unsigned long n)
146{
147 return FIND_NTH_BIT(addr1[idx] & addr2[idx], size, n);
148}
149EXPORT_SYMBOL(__find_nth_and_bit);
150
151unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
152 unsigned long size, unsigned long n)
153{
154 return FIND_NTH_BIT(addr1[idx] & ~addr2[idx], size, n);
155}
156EXPORT_SYMBOL(__find_nth_andnot_bit);
157
158#ifndef find_next_and_bit
159unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
160 unsigned long nbits, unsigned long start)
161{
162 return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
163}
164EXPORT_SYMBOL(_find_next_and_bit);
165#endif
166
167#ifndef find_next_andnot_bit
168unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
169 unsigned long nbits, unsigned long start)
170{
171 return FIND_NEXT_BIT(addr1[idx] & ~addr2[idx], /* nop */, nbits, start);
172}
173EXPORT_SYMBOL(_find_next_andnot_bit);
174#endif
175
176#ifndef find_next_zero_bit
177unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
178 unsigned long start)
179{
180 return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
181}
182EXPORT_SYMBOL(_find_next_zero_bit);
183#endif
184
185#ifndef find_last_bit
186unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
187{
188 if (size) {
189 unsigned long val = BITMAP_LAST_WORD_MASK(size);
190 unsigned long idx = (size-1) / BITS_PER_LONG;
191
192 do {
193 val &= addr[idx];
194 if (val)
195 return idx * BITS_PER_LONG + __fls(val);
196
197 val = ~0ul;
198 } while (idx--);
199 }
200 return size;
201}
202EXPORT_SYMBOL(_find_last_bit);
203#endif
204
205unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
206 unsigned long size, unsigned long offset)
207{
208 offset = find_next_bit(addr, size, offset);
209 if (offset == size)
210 return size;
211
212 offset = round_down(offset, 8);
213 *clump = bitmap_get_value8(addr, offset);
214
215 return offset;
216}
217EXPORT_SYMBOL(find_next_clump8);
218
219#ifdef __BIG_ENDIAN
220
221#ifndef find_first_zero_bit_le
222/*
223 * Find the first cleared bit in an LE memory region.
224 */
225unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
226{
227 return FIND_FIRST_BIT(~addr[idx], swab, size);
228}
229EXPORT_SYMBOL(_find_first_zero_bit_le);
230
231#endif
232
233#ifndef find_next_zero_bit_le
234unsigned long _find_next_zero_bit_le(const unsigned long *addr,
235 unsigned long size, unsigned long offset)
236{
237 return FIND_NEXT_BIT(~addr[idx], swab, size, offset);
238}
239EXPORT_SYMBOL(_find_next_zero_bit_le);
240#endif
241
242#ifndef find_next_bit_le
243unsigned long _find_next_bit_le(const unsigned long *addr,
244 unsigned long size, unsigned long offset)
245{
246 return FIND_NEXT_BIT(addr[idx], swab, size, offset);
247}
248EXPORT_SYMBOL(_find_next_bit_le);
249
250#endif
251
252#endif /* __BIG_ENDIAN */