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