1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Crypto library utility functions
4 *
5 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
6 */
7
8#include <asm/unaligned.h>
9#include <crypto/utils.h>
10#include <linux/module.h>
11
12/*
13 * XOR @len bytes from @src1 and @src2 together, writing the result to @dst
14 * (which may alias one of the sources).  Don't call this directly; call
15 * crypto_xor() or crypto_xor_cpy() instead.
16 */
17void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len)
18{
19	int relalign = 0;
20
21	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
22		int size = sizeof(unsigned long);
23		int d = (((unsigned long)dst ^ (unsigned long)src1) |
24			 ((unsigned long)dst ^ (unsigned long)src2)) &
25			(size - 1);
26
27		relalign = d ? 1 << __ffs(d) : size;
28
29		/*
30		 * If we care about alignment, process as many bytes as
31		 * needed to advance dst and src to values whose alignments
32		 * equal their relative alignment. This will allow us to
33		 * process the remainder of the input using optimal strides.
34		 */
35		while (((unsigned long)dst & (relalign - 1)) && len > 0) {
36			*dst++ = *src1++ ^ *src2++;
37			len--;
38		}
39	}
40
41	while (IS_ENABLED(CONFIG_64BIT) && len >= 8 && !(relalign & 7)) {
42		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
43			u64 l = get_unaligned((u64 *)src1) ^
44				get_unaligned((u64 *)src2);
45			put_unaligned(l, (u64 *)dst);
46		} else {
47			*(u64 *)dst = *(u64 *)src1 ^ *(u64 *)src2;
48		}
49		dst += 8;
50		src1 += 8;
51		src2 += 8;
52		len -= 8;
53	}
54
55	while (len >= 4 && !(relalign & 3)) {
56		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
57			u32 l = get_unaligned((u32 *)src1) ^
58				get_unaligned((u32 *)src2);
59			put_unaligned(l, (u32 *)dst);
60		} else {
61			*(u32 *)dst = *(u32 *)src1 ^ *(u32 *)src2;
62		}
63		dst += 4;
64		src1 += 4;
65		src2 += 4;
66		len -= 4;
67	}
68
69	while (len >= 2 && !(relalign & 1)) {
70		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
71			u16 l = get_unaligned((u16 *)src1) ^
72				get_unaligned((u16 *)src2);
73			put_unaligned(l, (u16 *)dst);
74		} else {
75			*(u16 *)dst = *(u16 *)src1 ^ *(u16 *)src2;
76		}
77		dst += 2;
78		src1 += 2;
79		src2 += 2;
80		len -= 2;
81	}
82
83	while (len--)
84		*dst++ = *src1++ ^ *src2++;
85}
86EXPORT_SYMBOL_GPL(__crypto_xor);
87
88MODULE_LICENSE("GPL");
89