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
  25 static 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
  33 void 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 }
  41 EXPORT_SYMBOL_GPL(scatterwalk_start);
  42
  43 void *scatterwalk_map(struct scatter_walk *walk)
  44 {
  45         return kmap_atomic(scatterwalk_page(walk)) +
  46                offset_in_page(walk->offset);
  47 }
  48 EXPORT_SYMBOL_GPL(scatterwalk_map);
  49
  50 static 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, sg_next(walk->sg));
  66         }
  67 }
  68
  69 void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  70 {
  71         if (!more || walk->offset >= walk->sg->offset + walk->sg->length ||
  72             !(walk->offset & (PAGE_SIZE - 1)))
  73                 scatterwalk_pagedone(walk, out, more);
  74 }
  75 EXPORT_SYMBOL_GPL(scatterwalk_done);
  76
  77 void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  78                             size_t nbytes, int out)
  79 {
  80         for (;;) {
  81                 unsigned int len_this_page = scatterwalk_pagelen(walk);
  82                 u8 *vaddr;
  83
  84                 if (len_this_page > nbytes)
  85                         len_this_page = nbytes;
  86
  87                 vaddr = scatterwalk_map(walk);
  88                 memcpy_dir(buf, vaddr, len_this_page, out);
  89                 scatterwalk_unmap(vaddr);
  90
  91                 scatterwalk_advance(walk, len_this_page);
  92
  93                 if (nbytes == len_this_page)
  94                         break;
  95
  96                 buf += len_this_page;
  97                 nbytes -= len_this_page;
  98
  99                 scatterwalk_pagedone(walk, out, 1);
 100         }
 101 }
 102 EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
 103
 104 void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
 105                               unsigned int start, unsigned int nbytes, int out)
 106 {
 107         struct scatter_walk walk;
 108         unsigned int offset = 0;
 109
 110         if (!nbytes)
 111                 return;
 112
 113         for (;;) {
 114                 scatterwalk_start(&walk, sg);
 115
 116                 if (start < offset + sg->length)
 117                         break;
 118
 119                 offset += sg->length;
 120                 sg = sg_next(sg);
 121         }
 122
 123         scatterwalk_advance(&walk, start - offset);
 124         scatterwalk_copychunks(buf, &walk, nbytes, out);
 125         scatterwalk_done(&walk, out, 0);
 126 }
 127 EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
 128
 129 int scatterwalk_bytes_sglen(struct scatterlist *sg, int num_bytes)
 130 {
 131         int offset = 0, n = 0;
 132
 133         /* num_bytes is too small */
 134         if (num_bytes < sg->length)
 135                 return -1;
 136
 137         do {
 138                 offset += sg->length;
 139                 n++;
 140                 sg = sg_next(sg);
 141
 142                 /* num_bytes is too large */
 143                 if (unlikely(!sg && (num_bytes < offset)))
 144                         return -1;
 145         } while (sg && (num_bytes > offset));
 146
 147         return n;
 148 }
 149 EXPORT_SYMBOL_GPL(scatterwalk_bytes_sglen);