lib/crypto/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 <linux/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  */
  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_DESCRIPTION("Crypto library utility functions");
  89 MODULE_LICENSE("GPL");