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);