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 */
__crypto_xor(u8 * dst,const u8 * src1,const u8 * src2,unsigned int len)18 void __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 }
87 EXPORT_SYMBOL_GPL(__crypto_xor);
88
89 MODULE_DESCRIPTION("Crypto library utility functions");
90 MODULE_LICENSE("GPL");
91