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 */ 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