1#ifndef _ASM_WORD_AT_A_TIME_H
  2#define _ASM_WORD_AT_A_TIME_H
  3
  4#include <linux/kernel.h>
  5
  6/*
  7 * This is largely generic for little-endian machines, but the
  8 * optimal byte mask counting is probably going to be something
  9 * that is architecture-specific. If you have a reliably fast
 10 * bit count instruction, that might be better than the multiply
 11 * and shift, for example.
 12 */
 13struct word_at_a_time {
 14	const unsigned long one_bits, high_bits;
 15};
 16
 17#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
 18
 19#ifdef CONFIG_64BIT
 20
 21/*
 22 * Jan Achrenius on G+: microoptimized version of
 23 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
 24 * that works for the bytemasks without having to
 25 * mask them first.
 26 */
 27static inline long count_masked_bytes(unsigned long mask)
 28{
 29	return mask*0x0001020304050608ul >> 56;
 30}
 31
 32#else	/* 32-bit case */
 33
 34/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
 35static inline long count_masked_bytes(long mask)
 36{
 37	/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
 38	long a = (0x0ff0001+mask) >> 23;
 39	/* Fix the 1 for 00 case */
 40	return a & mask;
 41}
 42
 43#endif
 44
 45/* Return nonzero if it has a zero */
 46static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
 47{
 48	unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
 49	*bits = mask;
 50	return mask;
 51}
 52
 53static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
 54{
 55	return bits;
 56}
 57
 58static inline unsigned long create_zero_mask(unsigned long bits)
 59{
 60	bits = (bits - 1) & ~bits;
 61	return bits >> 7;
 62}
 63
 64/* The mask we created is directly usable as a bytemask */
 65#define zero_bytemask(mask) (mask)
 66
 67static inline unsigned long find_zero(unsigned long mask)
 68{
 69	return count_masked_bytes(mask);
 70}
 71
 72/*
 73 * Load an unaligned word from kernel space.
 74 *
 75 * In the (very unlikely) case of the word being a page-crosser
 76 * and the next page not being mapped, take the exception and
 77 * return zeroes in the non-existing part.
 78 */
 79static inline unsigned long load_unaligned_zeropad(const void *addr)
 80{
 81	unsigned long ret, dummy;
 82
 83	asm(
 84		"1:\tmov %2,%0\n"
 85		"2:\n"
 86		".section .fixup,\"ax\"\n"
 87		"3:\t"
 88		"lea %2,%1\n\t"
 89		"and %3,%1\n\t"
 90		"mov (%1),%0\n\t"
 91		"leal %2,%%ecx\n\t"
 92		"andl %4,%%ecx\n\t"
 93		"shll $3,%%ecx\n\t"
 94		"shr %%cl,%0\n\t"
 95		"jmp 2b\n"
 96		".previous\n"
 97		_ASM_EXTABLE(1b, 3b)
 98		:"=&r" (ret),"=&c" (dummy)
 99		:"m" (*(unsigned long *)addr),
100		 "i" (-sizeof(unsigned long)),
101		 "i" (sizeof(unsigned long)-1));
102	return ret;
103}
104
105#endif /* _ASM_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/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 */