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scatterwalk.c

/*
 * 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 <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/scatterlist.h>

#include "internal.h"
#include "scatterwalk.h"

static inline void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
{
      void *src = out ? buf : sgdata;
      void *dst = out ? sgdata : buf;

      memcpy(dst, src, nbytes);
}

void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
{
      walk->sg = sg;

      BUG_ON(!sg->length);

      walk->offset = sg->offset;
}
EXPORT_SYMBOL_GPL(scatterwalk_start);

void *scatterwalk_map(struct scatter_walk *walk, int out)
{
      return crypto_kmap(scatterwalk_page(walk), out) +
             offset_in_page(walk->offset);
}
EXPORT_SYMBOL_GPL(scatterwalk_map);

static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
                         unsigned int more)
{
      if (out) {
            struct page *page;

            page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
            flush_dcache_page(page);
      }

      if (more) {
            walk->offset += PAGE_SIZE - 1;
            walk->offset &= PAGE_MASK;
            if (walk->offset >= walk->sg->offset + walk->sg->length)
                  scatterwalk_start(walk, scatterwalk_sg_next(walk->sg));
      }
}

void scatterwalk_done(struct scatter_walk *walk, int out, int more)
{
      if (!offset_in_page(walk->offset) || !more)
            scatterwalk_pagedone(walk, out, more);
}
EXPORT_SYMBOL_GPL(scatterwalk_done);

void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
                      size_t nbytes, int out)
{
      for (;;) {
            unsigned int len_this_page = scatterwalk_pagelen(walk);
            u8 *vaddr;

            if (len_this_page > nbytes)
                  len_this_page = nbytes;

            vaddr = scatterwalk_map(walk, out);
            memcpy_dir(buf, vaddr, len_this_page, out);
            scatterwalk_unmap(vaddr, out);

            scatterwalk_advance(walk, len_this_page);

            if (nbytes == len_this_page)
                  break;

            buf += len_this_page;
            nbytes -= len_this_page;

            scatterwalk_pagedone(walk, out, 1);
      }
}
EXPORT_SYMBOL_GPL(scatterwalk_copychunks);

void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
                        unsigned int start, unsigned int nbytes, int out)
{
      struct scatter_walk walk;
      unsigned int offset = 0;

      for (;;) {
            scatterwalk_start(&walk, sg);

            if (start < offset + sg->length)
                  break;

            offset += sg->length;
            sg = sg_next(sg);
      }

      scatterwalk_advance(&walk, start - offset);
      scatterwalk_copychunks(buf, &walk, nbytes, out);
      scatterwalk_done(&walk, out, 0);
}
EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);

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