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 #include <linux/kernel.h>
  17 #include <linux/mm.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/highmem.h>
  20 #include <asm/scatterlist.h>
  21 #include "internal.h"
  22 #include "scatterwalk.h"
  23
  24 enum km_type crypto_km_types[] = {
  25         KM_USER0,
  26         KM_USER1,
  27         KM_SOFTIRQ0,
  28         KM_SOFTIRQ1,
  29 };
  30
  31 void *scatterwalk_whichbuf(struct scatter_walk *walk, unsigned int nbytes, void *scratch)
  32 {
  33         if (nbytes <= walk->len_this_page &&
  34             (((unsigned long)walk->data) & (PAGE_CACHE_SIZE - 1)) + nbytes <=
  35             PAGE_CACHE_SIZE)
  36                 return walk->data;
  37         else
  38                 return scratch;
  39 }
  40
  41 static void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
  42 {
  43         if (out)
  44                 memcpy(sgdata, buf, nbytes);
  45         else
  46                 memcpy(buf, sgdata, nbytes);
  47 }
  48
  49 void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
  50 {
  51         unsigned int rest_of_page;
  52
  53         walk->sg = sg;
  54
  55         walk->page = sg->page;
  56         walk->len_this_segment = sg->length;
  57
  58         rest_of_page = PAGE_CACHE_SIZE - (sg->offset & (PAGE_CACHE_SIZE - 1));
  59         walk->len_this_page = min(sg->length, rest_of_page);
  60         walk->offset = sg->offset;
  61 }
  62
  63 void scatterwalk_map(struct scatter_walk *walk, int out)
  64 {
  65         walk->data = crypto_kmap(walk->page, out) + walk->offset;
  66 }
  67
  68 static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  69                                  unsigned int more)
  70 {
  71         /* walk->data may be pointing the first byte of the next page;
  72            however, we know we transfered at least one byte.  So,
  73            walk->data - 1 will be a virtual address in the mapped page. */
  74
  75         if (out)
  76                 flush_dcache_page(walk->page);
  77
  78         if (more) {
  79                 walk->len_this_segment -= walk->len_this_page;
  80
  81                 if (walk->len_this_segment) {
  82                         walk->page++;
  83                         walk->len_this_page = min(walk->len_this_segment,
  84                                                   (unsigned)PAGE_CACHE_SIZE);
  85                         walk->offset = 0;
  86                 }
  87                 else
  88                         scatterwalk_start(walk, sg_next(walk->sg));
  89         }
  90 }
  91
  92 void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  93 {
  94         crypto_kunmap(walk->data, out);
  95         if (walk->len_this_page == 0 || !more)
  96                 scatterwalk_pagedone(walk, out, more);
  97 }
  98
  99 /*
 100  * Do not call this unless the total length of all of the fragments
 101  * has been verified as multiple of the block size.
 102  */
 103 int scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
 104                            size_t nbytes, int out)
 105 {
 106         if (buf != walk->data) {
 107                 while (nbytes > walk->len_this_page) {
 108                         memcpy_dir(buf, walk->data, walk->len_this_page, out);
 109                         buf += walk->len_this_page;
 110                         nbytes -= walk->len_this_page;
 111
 112                         crypto_kunmap(walk->data, out);
 113                         scatterwalk_pagedone(walk, out, 1);
 114                         scatterwalk_map(walk, out);
 115                 }
 116
 117                 memcpy_dir(buf, walk->data, nbytes, out);
 118         }
 119
 120         walk->offset += nbytes;
 121         walk->len_this_page -= nbytes;
 122         walk->len_this_segment -= nbytes;
 123         return 0;
 124 }