LXR linux/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
  25static 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
  33void 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}
  41EXPORT_SYMBOL_GPL(scatterwalk_start);
  42
  43void *scatterwalk_map(struct scatter_walk *walk, int out)
  44{
  45        return crypto_kmap(scatterwalk_page(walk), out) +
  46               offset_in_page(walk->offset);
  47}
  48EXPORT_SYMBOL_GPL(scatterwalk_map);
  49
  50static 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                flush_dcache_page(page);
  58        }
  59
  60        if (more) {
  61                walk->offset += PAGE_SIZE - 1;
  62                walk->offset &= PAGE_MASK;
  63                if (walk->offset >= walk->sg->offset + walk->sg->length)
  64                        scatterwalk_start(walk, scatterwalk_sg_next(walk->sg));
  65        }
  66}
  67
  68void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  69{
  70        if (!offset_in_page(walk->offset) || !more)
  71                scatterwalk_pagedone(walk, out, more);
  72}
  73EXPORT_SYMBOL_GPL(scatterwalk_done);
  74
  75void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  76                            size_t nbytes, int out)
  77{
  78        for (;;) {
  79                unsigned int len_this_page = scatterwalk_pagelen(walk);
  80                u8 *vaddr;
  81
  82                if (len_this_page > nbytes)
  83                        len_this_page = nbytes;
  84
  85                vaddr = scatterwalk_map(walk, out);
  86                memcpy_dir(buf, vaddr, len_this_page, out);
  87                scatterwalk_unmap(vaddr, out);
  88
  89                scatterwalk_advance(walk, len_this_page);
  90
  91                if (nbytes == len_this_page)
  92                        break;
  93
  94                buf += len_this_page;
  95                nbytes -= len_this_page;
  96
  97                scatterwalk_pagedone(walk, out, 1);
  98        }
  99}
 100EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
 101
 102void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
 103                              unsigned int start, unsigned int nbytes, int out)
 104{
 105        struct scatter_walk walk;
 106        unsigned int offset = 0;
 107
 108        if (!nbytes)
 109                return;
 110
 111        for (;;) {
 112                scatterwalk_start(&walk, sg);
 113
 114                if (start < offset + sg->length)
 115                        break;
 116
 117                offset += sg->length;
 118                sg = scatterwalk_sg_next(sg);
 119        }
 120
 121        scatterwalk_advance(&walk, start - offset);
 122        scatterwalk_copychunks(buf, &walk, nbytes, out);
 123        scatterwalk_done(&walk, out, 0);
 124}
 125EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
 126