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