utils.c

 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 <crypto/utils.h>
 9#include <linux/export.h>
10#include <linux/module.h>
11#include <linux/unaligned.h>
12
13/*
14 * XOR @len bytes from @src1 and @src2 together, writing the result to @dst
15 * (which may alias one of the sources).  Don't call this directly; call
16 * crypto_xor() or crypto_xor_cpy() instead.
17 */
18void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len)
19{
20	int relalign = 0;
21
22	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
23		int size = sizeof(unsigned long);
24		int d = (((unsigned long)dst ^ (unsigned long)src1) |
25			 ((unsigned long)dst ^ (unsigned long)src2)) &
26			(size - 1);
27
28		relalign = d ? 1 << __ffs(d) : size;
29
30		/*
31		 * If we care about alignment, process as many bytes as
32		 * needed to advance dst and src to values whose alignments
33		 * equal their relative alignment. This will allow us to
34		 * process the remainder of the input using optimal strides.
35		 */
36		while (((unsigned long)dst & (relalign - 1)) && len > 0) {
37			*dst++ = *src1++ ^ *src2++;
38			len--;
39		}
40	}
41
42	while (IS_ENABLED(CONFIG_64BIT) && len >= 8 && !(relalign & 7)) {
43		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
44			u64 l = get_unaligned((u64 *)src1) ^
45				get_unaligned((u64 *)src2);
46			put_unaligned(l, (u64 *)dst);
47		} else {
48			*(u64 *)dst = *(u64 *)src1 ^ *(u64 *)src2;
49		}
50		dst += 8;
51		src1 += 8;
52		src2 += 8;
53		len -= 8;
54	}
55
56	while (len >= 4 && !(relalign & 3)) {
57		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
58			u32 l = get_unaligned((u32 *)src1) ^
59				get_unaligned((u32 *)src2);
60			put_unaligned(l, (u32 *)dst);
61		} else {
62			*(u32 *)dst = *(u32 *)src1 ^ *(u32 *)src2;
63		}
64		dst += 4;
65		src1 += 4;
66		src2 += 4;
67		len -= 4;
68	}
69
70	while (len >= 2 && !(relalign & 1)) {
71		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
72			u16 l = get_unaligned((u16 *)src1) ^
73				get_unaligned((u16 *)src2);
74			put_unaligned(l, (u16 *)dst);
75		} else {
76			*(u16 *)dst = *(u16 *)src1 ^ *(u16 *)src2;
77		}
78		dst += 2;
79		src1 += 2;
80		src2 += 2;
81		len -= 2;
82	}
83
84	while (len--)
85		*dst++ = *src1++ ^ *src2++;
86}
87EXPORT_SYMBOL_GPL(__crypto_xor);
88
89MODULE_DESCRIPTION("Crypto library utility functions");
90MODULE_LICENSE("GPL");