LXR RHEL4/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
  24enum km_type crypto_km_types[] = {
  25        KM_USER0,
  26        KM_USER1,
  27        KM_SOFTIRQ0,
  28        KM_SOFTIRQ1,
  29};
  30
  31void *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
  41static 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
  49void 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
  63void scatterwalk_map(struct scatter_walk *walk, int out)
  64{
  65        walk->data = crypto_kmap(walk->page, out) + walk->offset;
  66}
  67
  68static 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
  92void 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 */
 103int 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}
 125