scatterwalk.c

Go to the documentation of this file.

/*
 * Cryptographic API.
 *
 * Cipher operations.
 *
 * Copyright (c) 2002 James Morris <[email protected]>
 *               2002 Adam J. Richter <[email protected]>
 *               2004 Jean-Luc Cooke <[email protected]>
 *
 * 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)
{
    return kmap_atomic(scatterwalk_page(walk)) +
           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);
        if (!PageSlab(page))
            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 (!(scatterwalk_pagelen(walk) & (PAGE_SIZE - 1)) || !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);
        memcpy_dir(buf, vaddr, len_this_page, out);
        scatterwalk_unmap(vaddr);

        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);