root/crypto/scatterwalk.c

DEFINITIONS

1. memcpy_dir
2. scatterwalk_start
3. scatterwalk_map
4. scatterwalk_pagedone
5. scatterwalk_done
6. scatterwalk_copychunks
7. scatterwalk_map_and_copy

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

        if (!nbytes)
                return;

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

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

                offset += sg->length;
                sg = scatterwalk_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);