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 static void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
  32 {
  33         if (out)
  34                 memcpy(sgdata, buf, nbytes);
  35         else
  36                 memcpy(buf, sgdata, nbytes);
  37 }
  38
  39 void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
  40 {
  41         unsigned int rest_of_page;
  42
  43         walk->sg = sg;
  44
  45         walk->page = sg->page;
  46         walk->len_this_segment = sg->length;
  47
  48         BUG_ON(!sg->length);
  49
  50         rest_of_page = PAGE_CACHE_SIZE - (sg->offset & (PAGE_CACHE_SIZE - 1));
  51         walk->len_this_page = min(sg->length, rest_of_page);
  52         walk->offset = sg->offset;
  53 }
  54
  55 void scatterwalk_map(struct scatter_walk *walk, int out)
  56 {
  57         walk->data = crypto_kmap(walk->page, out) + walk->offset;
  58 }
  59
  60 static inline void scatterwalk_unmap(struct scatter_walk *walk, int out)
  61 {
  62         /* walk->data may be pointing the first byte of the next page;
  63            however, we know we transfered at least one byte.  So,
  64            walk->data - 1 will be a virtual address in the mapped page. */
  65         crypto_kunmap(walk->data - 1, out);
  66 }
  67
  68 static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  69                                  unsigned int more)
  70 {
  71         if (out)
  72                 flush_dcache_page(walk->page);
  73
  74         if (more) {
  75                 walk->len_this_segment -= walk->len_this_page;
  76
  77                 if (walk->len_this_segment) {
  78                         walk->page++;
  79                         walk->len_this_page = min(walk->len_this_segment,
  80                                                   (unsigned)PAGE_CACHE_SIZE);
  81                         walk->offset = 0;
  82                 }
  83                 else
  84                         scatterwalk_start(walk, sg_next(walk->sg));
  85         }
  86 }
  87
  88 void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  89 {
  90         scatterwalk_unmap(walk, out);
  91         if (walk->len_this_page == 0 || !more)
  92                 scatterwalk_pagedone(walk, out, more);
  93 }
  94
  95 /*
  96  * Do not call this unless the total length of all of the fragments
  97  * has been verified as multiple of the block size.
  98  */
  99 int scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
 100                            size_t nbytes, int out)
 101 {
 102         while (nbytes > walk->len_this_page) {
 103                 memcpy_dir(buf, walk->data, walk->len_this_page, out);
 104                 buf += walk->len_this_page;
 105                 nbytes -= walk->len_this_page;
 106
 107                 scatterwalk_unmap(walk, out);
 108                 scatterwalk_pagedone(walk, out, 1);
 109                 scatterwalk_map(walk, out);
 110         }
 111
 112         memcpy_dir(buf, walk->data, nbytes, out);
 113         return nbytes;
 114 }