text: /*
   * Cryptographic API.
   *
   * Cipher operations.
   *
   * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   *               2002 Adam J. Richter <adam@yggdrasil.com>
   *               2004 Jean-Luc Cooke <jlcooke@certainkey.com>
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the Free
   * Software Foundation; either version 2 of the License, or (at your option)
   * any later version.
   *
   */
  #include "kmap_types.h"
  
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/pagemap.h>
  #include <linux/highmem.h>
  #include <asm/scatterlist.h>
  #include "internal.h"
  #include "scatterwalk.h"
  
  enum km_type crypto_km_types[] = {
  	KM_USER0,
  	KM_USER1,
  	KM_SOFTIRQ0,
  	KM_SOFTIRQ1,
  };
  
  void *scatterwalk_whichbuf(struct scatter_walk *walk, unsigned int nbytes, void *scratch)
  {
  	if (nbytes <= walk->len_this_page &&
  	    (((unsigned long)walk->data) & (PAGE_CACHE_SIZE - 1)) + nbytes <=
  	    PAGE_CACHE_SIZE)
  		return walk->data;
  	else
  		return scratch;
  }
  
  static void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
  {
  	if (out)
  		memcpy(sgdata, buf, nbytes);
  	else
  		memcpy(buf, sgdata, nbytes);
  }
  
  void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
  {
  	unsigned int rest_of_page;
  
  	walk->sg = sg;
  
  	walk->page = sg->page;
  	walk->len_this_segment = sg->length;
  
  	rest_of_page = PAGE_CACHE_SIZE - (sg->offset & (PAGE_CACHE_SIZE - 1));
  	walk->len_this_page = min(sg->length, rest_of_page);
  	walk->offset = sg->offset;
  }
  
  void scatterwalk_map(struct scatter_walk *walk, int out)
  {
  	walk->data = crypto_kmap(walk->page, out) + walk->offset;
  }
  
  static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
  				 unsigned int more)
  {
  	/* walk->data may be pointing the first byte of the next page;
  	   however, we know we transferred at least one byte.  So,
  	   walk->data - 1 will be a virtual address in the mapped page. */
  
  	if (out)
  		flush_dcache_page(walk->page);
  
  	if (more) {
  		walk->len_this_segment -= walk->len_this_page;
  
  		if (walk->len_this_segment) {
  			walk->page++;
  			walk->len_this_page = min(walk->len_this_segment,
  						  (unsigned)PAGE_CACHE_SIZE);
  			walk->offset = 0;
  		}
  		else
  			scatterwalk_start(walk, sg_next(walk->sg));
  	}
  }
  
  void scatterwalk_done(struct scatter_walk *walk, int out, int more)
  {
  	crypto_kunmap(walk->data, out);
  	if (walk->len_this_page == 0 || !more)
  		scatterwalk_pagedone(walk, out, more);
  }
  
  /*
   * Do not call this unless the total length of all of the fragments
   * has been verified as multiple of the block size.
   */
  int scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
  			   size_t nbytes, int out)
  {
  	if (buf != walk->data) {
  		while (nbytes > walk->len_this_page) {
  			memcpy_dir(buf, walk->data, walk->len_this_page, out);
  			buf += walk->len_this_page;
  			nbytes -= walk->len_this_page;
  
  			crypto_kunmap(walk->data, out);
  			scatterwalk_pagedone(walk, out, 1);
  			scatterwalk_map(walk, out);
  		}
  
  		memcpy_dir(buf, walk->data, nbytes, out);
  	}
  
  	walk->offset += nbytes;
  	walk->len_this_page -= nbytes;
  	walk->len_this_segment -= nbytes;
  	return 0;
  }
  