drivers/staging/rtl8192u/ieee80211/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
  24 void *scatterwalk_whichbuf(struct scatter_walk *walk, unsigned int nbytes, void *scratch)
  25 {
  26         if (nbytes <= walk->len_this_page &&
  27             (((unsigned long)walk->data) & (PAGE_CACHE_SIZE - 1)) + nbytes <=
  28             PAGE_CACHE_SIZE)
  29                 return walk->data;
  30         else
  31                 return scratch;
  32 }
  33
  34 static void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
  35 {
  36         if (out)
  37                 memcpy(sgdata, buf, nbytes);
  38         else
  39                 memcpy(buf, sgdata, nbytes);
  40 }
  41
  42 void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
  43 {
  44         unsigned int rest_of_page;
  45
  46         walk->sg = sg;
  47
  48         walk->page = sg->page;
  49         walk->len_this_segment = sg->length;
  50
  51         rest_of_page = PAGE_CACHE_SIZE - (sg->offset & (PAGE_CACHE_SIZE - 1));
  52         walk->len_this_page = min(sg->length, rest_of_page);
  53         walk->offset = sg->offset;
  54 }
  55
  56 void scatterwalk_map(struct scatter_walk *walk)
  57 {
  58         walk->data = kmap_atomic(walk->page) + walk->offset;
  59 }
  60
  61 static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  62                                  unsigned int more)
  63 {
  64         /* walk->data may be pointing the first byte of the next page;
  65            however, we know we transferred at least one byte.  So,
  66            walk->data - 1 will be a virtual address in the mapped page. */
  67
  68         if (out)
  69                 flush_dcache_page(walk->page);
  70
  71         if (more) {
  72                 walk->len_this_segment -= walk->len_this_page;
  73
  74                 if (walk->len_this_segment) {
  75                         walk->page++;
  76                         walk->len_this_page = min(walk->len_this_segment,
  77                                                   (unsigned)PAGE_CACHE_SIZE);
  78                         walk->offset = 0;
  79                 }
  80                 else
  81                         scatterwalk_start(walk, sg_next(walk->sg));
  82         }
  83 }
  84
  85 void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  86 {
  87         crypto_kunmap(walk->data, out);
  88         if (walk->len_this_page == 0 || !more)
  89                 scatterwalk_pagedone(walk, out, more);
  90 }
  91
  92 /*
  93  * Do not call this unless the total length of all of the fragments
  94  * has been verified as multiple of the block size.
  95  */
  96 int scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  97                            size_t nbytes)
  98 {
  99         if (buf != walk->data) {
 100                 while (nbytes > walk->len_this_page) {
 101                         memcpy_dir(buf, walk->data, walk->len_this_page, out);
 102                         buf += walk->len_this_page;
 103                         nbytes -= walk->len_this_page;
 104
 105                         kunmap_atomic(walk->data);
 106                         scatterwalk_pagedone(walk, out, 1);
 107                         scatterwalk_map(walk);
 108                 }
 109
 110                 memcpy_dir(buf, walk->data, nbytes, out);
 111         }
 112
 113         walk->offset += nbytes;
 114         walk->len_this_page -= nbytes;
 115         walk->len_this_segment -= nbytes;
 116         return 0;
 117 }