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/module.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/highmem.h>
  21 #include <linux/scatterlist.h>
  22
  23 #include "internal.h"
  24 #include "scatterwalk.h"
  25
  26 static inline void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
  27 {
  28         void *src = out ? buf : sgdata;
  29         void *dst = out ? sgdata : buf;
  30
  31         memcpy(dst, src, nbytes);
  32 }
  33
  34 void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
  35 {
  36         walk->sg = sg;
  37
  38         BUG_ON(!sg->length);
  39
  40         walk->offset = sg->offset;
  41 }
  42 EXPORT_SYMBOL_GPL(scatterwalk_start);
  43
  44 void *scatterwalk_map(struct scatter_walk *walk, int out)
  45 {
  46         return crypto_kmap(scatterwalk_page(walk), out) +
  47                offset_in_page(walk->offset);
  48 }
  49 EXPORT_SYMBOL_GPL(scatterwalk_map);
  50
  51 static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  52                                  unsigned int more)
  53 {
  54         if (out) {
  55                 struct page *page;
  56
  57                 page = walk->sg->page + ((walk->offset - 1) >> PAGE_SHIFT);
  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, sg_next(walk->sg));
  66         }
  67 }
  68
  69 void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  70 {
  71         if (!offset_in_page(walk->offset) || !more)
  72                 scatterwalk_pagedone(walk, out, more);
  73 }
  74 EXPORT_SYMBOL_GPL(scatterwalk_done);
  75
  76 void 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, out);
  87                 memcpy_dir(buf, vaddr, len_this_page, out);
  88                 scatterwalk_unmap(vaddr, out);
  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 }
 101 EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
 102
 103 void 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         for (;;) {
 110                 scatterwalk_start(&walk, sg);
 111
 112                 if (start < offset + sg->length)
 113                         break;
 114
 115                 offset += sg->length;
 116                 sg = sg_next(sg);
 117         }
 118
 119         scatterwalk_advance(&walk, start - offset);
 120         scatterwalk_copychunks(buf, &walk, nbytes, out);
 121         scatterwalk_done(&walk, out, 0);
 122 }
 123 EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);