crypto/scatterwalk.c

   1 /*
   2  * Cryptographic API.
   3  *
   4  * Cipher operations.
   5  *
   6  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   7  *               2002 Adam J. Richter <adam@yggdrasil.com>
   8  *               2004 Jean-Luc Cooke <jlcooke@certainkey.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify it
  11  * under the terms of the GNU General Public License as published by the Free
  12  * Software Foundation; either version 2 of the License, or (at your option)
  13  * any later version.
  14  *
  15  */
  16
  17 #include <crypto/scatterwalk.h>
  18 #include <linux/kernel.h>
  19 #include <linux/mm.h>
  20 #include <linux/module.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/highmem.h>
  23 #include <linux/scatterlist.h>
  24
  25 static inline void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
  26 {
  27         void *src = out ? buf : sgdata;
  28         void *dst = out ? sgdata : buf;
  29
  30         memcpy(dst, src, nbytes);
  31 }
  32
  33 void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
  34 {
  35         walk->sg = sg;
  36
  37         BUG_ON(!sg->length);
  38
  39         walk->offset = sg->offset;
  40 }
  41 EXPORT_SYMBOL_GPL(scatterwalk_start);
  42
  43 void *scatterwalk_map(struct scatter_walk *walk)
  44 {
  45         return kmap_atomic(scatterwalk_page(walk)) +
  46                offset_in_page(walk->offset);
  47 }
  48 EXPORT_SYMBOL_GPL(scatterwalk_map);
  49
  50 static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  51                                  unsigned int more)
  52 {
  53         if (out) {
  54                 struct page *page;
  55
  56                 page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
  57                 /* Test ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE first as
  58                  * PageSlab cannot be optimised away per se due to
  59                  * use of volatile pointer.
  60                  */
  61                 if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE && !PageSlab(page))
  62                         flush_dcache_page(page);
  63         }
  64
  65         if (more) {
  66                 walk->offset += PAGE_SIZE - 1;
  67                 walk->offset &= PAGE_MASK;
  68                 if (walk->offset >= walk->sg->offset + walk->sg->length)
  69                         scatterwalk_start(walk, sg_next(walk->sg));
  70         }
  71 }
  72
  73 void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  74 {
  75         if (!more || walk->offset >= walk->sg->offset + walk->sg->length ||
  76             !(walk->offset & (PAGE_SIZE - 1)))
  77                 scatterwalk_pagedone(walk, out, more);
  78 }
  79 EXPORT_SYMBOL_GPL(scatterwalk_done);
  80
  81 void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  82                             size_t nbytes, int out)
  83 {
  84         for (;;) {
  85                 unsigned int len_this_page = scatterwalk_pagelen(walk);
  86                 u8 *vaddr;
  87
  88                 if (len_this_page > nbytes)
  89                         len_this_page = nbytes;
  90
  91                 vaddr = scatterwalk_map(walk);
  92                 memcpy_dir(buf, vaddr, len_this_page, out);
  93                 scatterwalk_unmap(vaddr);
  94
  95                 scatterwalk_advance(walk, len_this_page);
  96
  97                 if (nbytes == len_this_page)
  98                         break;
  99
 100                 buf += len_this_page;
 101                 nbytes -= len_this_page;
 102
 103                 scatterwalk_pagedone(walk, out, 1);
 104         }
 105 }
 106 EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
 107
 108 void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
 109                               unsigned int start, unsigned int nbytes, int out)
 110 {
 111         struct scatter_walk walk;
 112         struct scatterlist tmp[2];
 113
 114         if (!nbytes)
 115                 return;
 116
 117         sg = scatterwalk_ffwd(tmp, sg, start);
 118
 119         if (sg_page(sg) == virt_to_page(buf) &&
 120             sg->offset == offset_in_page(buf))
 121                 return;
 122
 123         scatterwalk_start(&walk, sg);
 124         scatterwalk_copychunks(buf, &walk, nbytes, out);
 125         scatterwalk_done(&walk, out, 0);
 126 }
 127 EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
 128
 129 int scatterwalk_bytes_sglen(struct scatterlist *sg, int num_bytes)
 130 {
 131         int offset = 0, n = 0;
 132
 133         /* num_bytes is too small */
 134         if (num_bytes < sg->length)
 135                 return -1;
 136
 137         do {
 138                 offset += sg->length;
 139                 n++;
 140                 sg = sg_next(sg);
 141
 142                 /* num_bytes is too large */
 143                 if (unlikely(!sg && (num_bytes < offset)))
 144                         return -1;
 145         } while (sg && (num_bytes > offset));
 146
 147         return n;
 148 }
 149 EXPORT_SYMBOL_GPL(scatterwalk_bytes_sglen);
 150
 151 struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
 152                                      struct scatterlist *src,
 153                                      unsigned int len)
 154 {
 155         for (;;) {
 156                 if (!len)
 157                         return src;
 158
 159                 if (src->length > len)
 160                         break;
 161
 162                 len -= src->length;
 163                 src = sg_next(src);
 164         }
 165
 166         sg_init_table(dst, 2);
 167         sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
 168         scatterwalk_crypto_chain(dst, sg_next(src), 0, 2);
 169
 170         return dst;
 171 }
 172 EXPORT_SYMBOL_GPL(scatterwalk_ffwd);