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);			\
67 out:										\
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);			\
89 found:										\
90 	sz = min(idx * BITS_PER_LONG + fns(tmp, nr), sz);			\
91 out:										\
92 	sz;									\
93 })
94 
95 #ifndef find_first_bit
96 /*
97  * Find the first set bit in a memory region.
98  */
_find_first_bit(const unsigned long * addr,unsigned long size)99 unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
100 {
101 	return FIND_FIRST_BIT(addr[idx], /* nop */, size);
102 }
103 EXPORT_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  */
_find_first_and_bit(const unsigned long * addr1,const unsigned long * addr2,unsigned long size)110 unsigned 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 }
116 EXPORT_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  */
_find_first_zero_bit(const unsigned long * addr,unsigned long size)123 unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
124 {
125 	return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
126 }
127 EXPORT_SYMBOL(_find_first_zero_bit);
128 #endif
129 
130 #ifndef find_next_bit
_find_next_bit(const unsigned long * addr,unsigned long nbits,unsigned long start)131 unsigned 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 }
135 EXPORT_SYMBOL(_find_next_bit);
136 #endif
137 
__find_nth_bit(const unsigned long * addr,unsigned long size,unsigned long n)138 unsigned 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 }
142 EXPORT_SYMBOL(__find_nth_bit);
143 
__find_nth_and_bit(const unsigned long * addr1,const unsigned long * addr2,unsigned long size,unsigned long n)144 unsigned 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 }
149 EXPORT_SYMBOL(__find_nth_and_bit);
150 
__find_nth_andnot_bit(const unsigned long * addr1,const unsigned long * addr2,unsigned long size,unsigned long n)151 unsigned 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 }
156 EXPORT_SYMBOL(__find_nth_andnot_bit);
157 
__find_nth_and_andnot_bit(const unsigned long * addr1,const unsigned long * addr2,const unsigned long * addr3,unsigned long size,unsigned long n)158 unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1,
159 					const unsigned long *addr2,
160 					const unsigned long *addr3,
161 					unsigned long size, unsigned long n)
162 {
163 	return FIND_NTH_BIT(addr1[idx] & addr2[idx] & ~addr3[idx], size, n);
164 }
165 EXPORT_SYMBOL(__find_nth_and_andnot_bit);
166 
167 #ifndef find_next_and_bit
_find_next_and_bit(const unsigned long * addr1,const unsigned long * addr2,unsigned long nbits,unsigned long start)168 unsigned long _find_next_and_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 }
173 EXPORT_SYMBOL(_find_next_and_bit);
174 #endif
175 
176 #ifndef find_next_andnot_bit
_find_next_andnot_bit(const unsigned long * addr1,const unsigned long * addr2,unsigned long nbits,unsigned long start)177 unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
178 					unsigned long nbits, unsigned long start)
179 {
180 	return FIND_NEXT_BIT(addr1[idx] & ~addr2[idx], /* nop */, nbits, start);
181 }
182 EXPORT_SYMBOL(_find_next_andnot_bit);
183 #endif
184 
185 #ifndef find_next_zero_bit
_find_next_zero_bit(const unsigned long * addr,unsigned long nbits,unsigned long start)186 unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
187 					 unsigned long start)
188 {
189 	return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
190 }
191 EXPORT_SYMBOL(_find_next_zero_bit);
192 #endif
193 
194 #ifndef find_last_bit
_find_last_bit(const unsigned long * addr,unsigned long size)195 unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
196 {
197 	if (size) {
198 		unsigned long val = BITMAP_LAST_WORD_MASK(size);
199 		unsigned long idx = (size-1) / BITS_PER_LONG;
200 
201 		do {
202 			val &= addr[idx];
203 			if (val)
204 				return idx * BITS_PER_LONG + __fls(val);
205 
206 			val = ~0ul;
207 		} while (idx--);
208 	}
209 	return size;
210 }
211 EXPORT_SYMBOL(_find_last_bit);
212 #endif
213 
find_next_clump8(unsigned long * clump,const unsigned long * addr,unsigned long size,unsigned long offset)214 unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
215 			       unsigned long size, unsigned long offset)
216 {
217 	offset = find_next_bit(addr, size, offset);
218 	if (offset == size)
219 		return size;
220 
221 	offset = round_down(offset, 8);
222 	*clump = bitmap_get_value8(addr, offset);
223 
224 	return offset;
225 }
226 EXPORT_SYMBOL(find_next_clump8);
227 
228 #ifdef __BIG_ENDIAN
229 
230 #ifndef find_first_zero_bit_le
231 /*
232  * Find the first cleared bit in an LE memory region.
233  */
_find_first_zero_bit_le(const unsigned long * addr,unsigned long size)234 unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
235 {
236 	return FIND_FIRST_BIT(~addr[idx], swab, size);
237 }
238 EXPORT_SYMBOL(_find_first_zero_bit_le);
239 
240 #endif
241 
242 #ifndef find_next_zero_bit_le
_find_next_zero_bit_le(const unsigned long * addr,unsigned long size,unsigned long offset)243 unsigned long _find_next_zero_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 }
248 EXPORT_SYMBOL(_find_next_zero_bit_le);
249 #endif
250 
251 #ifndef find_next_bit_le
_find_next_bit_le(const unsigned long * addr,unsigned long size,unsigned long offset)252 unsigned long _find_next_bit_le(const unsigned long *addr,
253 				unsigned long size, unsigned long offset)
254 {
255 	return FIND_NEXT_BIT(addr[idx], swab, size, offset);
256 }
257 EXPORT_SYMBOL(_find_next_bit_le);
258 
259 #endif
260 
261 #endif /* __BIG_ENDIAN */
262