word-at-a-time.h

 1/* SPDX-License-Identifier: GPL-2.0-only */
 2/*
 3 * Copyright (C) 2013 ARM Ltd.
 4 */
 5#ifndef __ASM_WORD_AT_A_TIME_H
 6#define __ASM_WORD_AT_A_TIME_H
 7
 8#include <linux/uaccess.h>
 9
10#ifndef __AARCH64EB__
11
12#include <linux/bitops.h>
13#include <linux/wordpart.h>
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
21static inline unsigned long has_zero(unsigned long a, unsigned long *bits,
22				     const struct word_at_a_time *c)
23{
24	unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
25	*bits = mask;
26	return mask;
27}
28
29#define prep_zero_mask(a, bits, c) (bits)
30#define create_zero_mask(bits) (bits)
31#define find_zero(bits) (__ffs(bits) >> 3)
32
33static inline unsigned long zero_bytemask(unsigned long bits)
34{
35	bits = (bits - 1) & ~bits;
36	return bits >> 7;
37}
38
39#else	/* __AARCH64EB__ */
40#include <asm-generic/word-at-a-time.h>
41#endif
42
43/*
44 * Load an unaligned word from kernel space.
45 *
46 * In the (very unlikely) case of the word being a page-crosser
47 * and the next page not being mapped, take the exception and
48 * return zeroes in the non-existing part.
49 */
50static inline unsigned long load_unaligned_zeropad(const void *addr)
51{
52	unsigned long ret;
53
54	__mte_enable_tco_async();
55
56	/* Load word from unaligned pointer addr */
57	asm(
58	"1:	ldr	%0, %2\n"
59	"2:\n"
60	_ASM_EXTABLE_LOAD_UNALIGNED_ZEROPAD(1b, 2b, %0, %1)
61	: "=&r" (ret)
62	: "r" (addr), "Q" (*(unsigned long *)addr));
63
64	__mte_disable_tco_async();
65
66	return ret;
67}
68
69#endif /* __ASM_WORD_AT_A_TIME_H */