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                 if (out != 2) {
  92                         vaddr = scatterwalk_map(walk);
  93                         memcpy_dir(buf, vaddr, len_this_page, out);
  94                         scatterwalk_unmap(vaddr);
  95                 }
  96
  97                 scatterwalk_advance(walk, len_this_page);
  98
  99                 if (nbytes == len_this_page)
 100                         break;
 101
 102                 buf += len_this_page;
 103                 nbytes -= len_this_page;
 104
 105                 scatterwalk_pagedone(walk, out & 1, 1);
 106         }
 107 }
 108 EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
 109
 110 void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
 111                               unsigned int start, unsigned int nbytes, int out)
 112 {
 113         struct scatter_walk walk;
 114         struct scatterlist tmp[2];
 115
 116         if (!nbytes)
 117                 return;
 118
 119         sg = scatterwalk_ffwd(tmp, sg, start);
 120
 121         if (sg_page(sg) == virt_to_page(buf) &&
 122             sg->offset == offset_in_page(buf))
 123                 return;
 124
 125         scatterwalk_start(&walk, sg);
 126         scatterwalk_copychunks(buf, &walk, nbytes, out);
 127         scatterwalk_done(&walk, out, 0);
 128 }
 129 EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
 130
 131 struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
 132                                      struct scatterlist *src,
 133                                      unsigned int len)
 134 {
 135         for (;;) {
 136                 if (!len)
 137                         return src;
 138
 139                 if (src->length > len)
 140                         break;
 141
 142                 len -= src->length;
 143                 src = sg_next(src);
 144         }
 145
 146         sg_init_table(dst, 2);
 147         sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
 148         scatterwalk_crypto_chain(dst, sg_next(src), 0, 2);
 149
 150         return dst;
 151 }
 152 EXPORT_SYMBOL_GPL(scatterwalk_ffwd);