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/scatterlist.h>
  22
  23static inline void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
  24{
  25        void *src = out ? buf : sgdata;
  26        void *dst = out ? sgdata : buf;
  27
  28        memcpy(dst, src, nbytes);
  29}
  30
  31void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  32                            size_t nbytes, int out)
  33{
  34        for (;;) {
  35                unsigned int len_this_page = scatterwalk_pagelen(walk);
  36                u8 *vaddr;
  37
  38                if (len_this_page > nbytes)
  39                        len_this_page = nbytes;
  40
  41                if (out != 2) {
  42                        vaddr = scatterwalk_map(walk);
  43                        memcpy_dir(buf, vaddr, len_this_page, out);
  44                        scatterwalk_unmap(vaddr);
  45                }
  46
  47                scatterwalk_advance(walk, len_this_page);
  48
  49                if (nbytes == len_this_page)
  50                        break;
  51
  52                buf += len_this_page;
  53                nbytes -= len_this_page;
  54
  55                scatterwalk_pagedone(walk, out & 1, 1);
  56        }
  57}
  58EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
  59
  60void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
  61                              unsigned int start, unsigned int nbytes, int out)
  62{
  63        struct scatter_walk walk;
  64        struct scatterlist tmp[2];
  65
  66        if (!nbytes)
  67                return;
  68
  69        sg = scatterwalk_ffwd(tmp, sg, start);
  70
  71        scatterwalk_start(&walk, sg);
  72        scatterwalk_copychunks(buf, &walk, nbytes, out);
  73        scatterwalk_done(&walk, out, 0);
  74}
  75EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
  76
  77struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
  78                                     struct scatterlist *src,
  79                                     unsigned int len)
  80{
  81        for (;;) {
  82                if (!len)
  83                        return src;
  84
  85                if (src->length > len)
  86                        break;
  87
  88                len -= src->length;
  89                src = sg_next(src);
  90        }
  91
  92        sg_init_table(dst, 2);
  93        sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
  94        scatterwalk_crypto_chain(dst, sg_next(src), 0, 2);
  95
  96        return dst;
  97}
  98EXPORT_SYMBOL_GPL(scatterwalk_ffwd);
  99