1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_WORD_AT_A_TIME_H
3#define _ASM_WORD_AT_A_TIME_H
4
5#include <linux/bitops.h>
6#include <linux/wordpart.h>
7
8/*
9 * This is largely generic for little-endian machines, but the
10 * optimal byte mask counting is probably going to be something
11 * that is architecture-specific. If you have a reliably fast
12 * bit count instruction, that might be better than the multiply
13 * and shift, for example.
14 */
15struct word_at_a_time {
16	const unsigned long one_bits, high_bits;
17};
18
19#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
20
21#ifdef CONFIG_64BIT
22
23/*
24 * Jan Achrenius on G+: microoptimized version of
25 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
26 * that works for the bytemasks without having to
27 * mask them first.
28 */
29static inline long count_masked_bytes(unsigned long mask)
30{
31	return mask*0x0001020304050608ul >> 56;
32}
33
34#else	/* 32-bit case */
35
36/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
37static inline long count_masked_bytes(long mask)
38{
39	/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
40	long a = (0x0ff0001+mask) >> 23;
41	/* Fix the 1 for 00 case */
42	return a & mask;
43}
44
45#endif
46
47/* Return nonzero if it has a zero */
48static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
49{
50	unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
51	*bits = mask;
52	return mask;
53}
54
55static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
56{
57	return bits;
58}
59
60static inline unsigned long create_zero_mask(unsigned long bits)
61{
62	bits = (bits - 1) & ~bits;
63	return bits >> 7;
64}
65
66/* The mask we created is directly usable as a bytemask */
67#define zero_bytemask(mask) (mask)
68
69static inline unsigned long find_zero(unsigned long mask)
70{
71	return count_masked_bytes(mask);
72}
73
74/*
75 * Load an unaligned word from kernel space.
76 *
77 * In the (very unlikely) case of the word being a page-crosser
78 * and the next page not being mapped, take the exception and
79 * return zeroes in the non-existing part.
80 */
81static inline unsigned long load_unaligned_zeropad(const void *addr)
82{
83	unsigned long ret;
84
85	asm volatile(
86		"1:	mov %[mem], %[ret]\n"
87		"2:\n"
88		_ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_ZEROPAD)
89		: [ret] "=r" (ret)
90		: [mem] "m" (*(unsigned long *)addr));
91
92	return ret;
93}
94
95#endif /* _ASM_WORD_AT_A_TIME_H */
96