word-at-a-time.h

 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
 8struct word_at_a_time {
 9	const unsigned long one_bits, high_bits;
10};
11
12#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
13
14/* Return nonzero if it has a zero */
15static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
16{
17	unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
18	*bits = mask;
19	return mask;
20}
21
22static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
23{
24	return bits;
25}
26
27#ifdef CONFIG_64BIT
28
29/* Keep the initial has_zero() value for both bitmask and size calc */
30#define create_zero_mask(bits) (bits)
31
32static inline unsigned long zero_bytemask(unsigned long bits)
33{
34	bits = (bits - 1) & ~bits;
35	return bits >> 7;
36}
37
38#define find_zero(bits) (__ffs(bits) >> 3)
39
40#else
41
42/* Create the final mask for both bytemask and size */
43static inline unsigned long create_zero_mask(unsigned long bits)
44{
45	bits = (bits - 1) & ~bits;
46	return bits >> 7;
47}
48
49/* The mask we created is directly usable as a bytemask */
50#define zero_bytemask(mask) (mask)
51
52/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
53static inline unsigned long find_zero(unsigned long mask)
54{
55	/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
56	long a = (0x0ff0001+mask) >> 23;
57	/* Fix the 1 for 00 case */
58	return a & mask;
59}
60
61#endif
62
63/*
64 * Load an unaligned word from kernel space.
65 *
66 * In the (very unlikely) case of the word being a page-crosser
67 * and the next page not being mapped, take the exception and
68 * return zeroes in the non-existing part.
69 */
70static inline unsigned long load_unaligned_zeropad(const void *addr)
71{
72	unsigned long ret;
73
74	asm volatile(
75		"1:	mov %[mem], %[ret]\n"
76		"2:\n"
77		_ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_ZEROPAD)
78		: [ret] "=r" (ret)
79		: [mem] "m" (*(unsigned long *)addr));
80
81	return ret;
82}
83
84#endif /* _ASM_WORD_AT_A_TIME_H */