xref: /openbmc/linux/lib/crypto/utils.c (revision c616fb0c)
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  */
__crypto_xor(u8 * dst,const u8 * src1,const u8 * src2,unsigned int len)17 void __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 }
86 EXPORT_SYMBOL_GPL(__crypto_xor);
87 
88 MODULE_LICENSE("GPL");
89