linux/crypto/scatterwalk.c
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   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)
  44{
  45        return kmap_atomic(scatterwalk_page(walk)) +
  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                if (!PageSlab(page))
  58                        flush_dcache_page(page);
  59        }
  60
  61        if (more) {
  62                walk->offset += PAGE_SIZE - 1;
  63                walk->offset &= PAGE_MASK;
  64                if (walk->offset >= walk->sg->offset + walk->sg->length)
  65                        scatterwalk_start(walk, scatterwalk_sg_next(walk->sg));
  66        }
  67}
  68
  69void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  70{
  71        if (!(scatterwalk_pagelen(walk) & (PAGE_SIZE - 1)) || !more)
  72                scatterwalk_pagedone(walk, out, more);
  73}
  74EXPORT_SYMBOL_GPL(scatterwalk_done);
  75
  76void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  77                            size_t nbytes, int out)
  78{
  79        for (;;) {
  80                unsigned int len_this_page = scatterwalk_pagelen(walk);
  81                u8 *vaddr;
  82
  83                if (len_this_page > nbytes)
  84                        len_this_page = nbytes;
  85
  86                vaddr = scatterwalk_map(walk);
  87                memcpy_dir(buf, vaddr, len_this_page, out);
  88                scatterwalk_unmap(vaddr);
  89
  90                scatterwalk_advance(walk, len_this_page);
  91
  92                if (nbytes == len_this_page)
  93                        break;
  94
  95                buf += len_this_page;
  96                nbytes -= len_this_page;
  97
  98                scatterwalk_pagedone(walk, out, 1);
  99        }
 100}
 101EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
 102
 103void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
 104                              unsigned int start, unsigned int nbytes, int out)
 105{
 106        struct scatter_walk walk;
 107        unsigned int offset = 0;
 108
 109        if (!nbytes)
 110                return;
 111
 112        for (;;) {
 113                scatterwalk_start(&walk, sg);
 114
 115                if (start < offset + sg->length)
 116                        break;
 117
 118                offset += sg->length;
 119                sg = scatterwalk_sg_next(sg);
 120        }
 121
 122        scatterwalk_advance(&walk, start - offset);
 123        scatterwalk_copychunks(buf, &walk, nbytes, out);
 124        scatterwalk_done(&walk, out, 0);
 125}
 126EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
 127
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