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
 25static 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
 33void 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}
 41EXPORT_SYMBOL_GPL(scatterwalk_start);
 42
 43void *scatterwalk_map(struct scatter_walk *walk)
 44{
 45	return kmap_atomic(scatterwalk_page(walk)) +
 46	       offset_in_page(walk->offset);
 47}
 48EXPORT_SYMBOL_GPL(scatterwalk_map);
 49
 50static 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, scatterwalk_sg_next(walk->sg));
 66	}
 67}
 68
 69void scatterwalk_done(struct scatter_walk *walk, int out, int more)
 70{
 71	if (!(scatterwalk_pagelen(walk) & (PAGE_SIZE - 1)) || !more)
 72		scatterwalk_pagedone(walk, out, more);
 73}
 74EXPORT_SYMBOL_GPL(scatterwalk_done);
 75
 76void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
 77			    size_t nbytes, int out)
 78{
 79	for (;;) {
 80		unsigned int len_this_page = scatterwalk_pagelen(walk);
 81		u8 *vaddr;
 82
 83		if (len_this_page > nbytes)
 84			len_this_page = nbytes;
 85
 86		vaddr = scatterwalk_map(walk);
 87		memcpy_dir(buf, vaddr, len_this_page, out);
 88		scatterwalk_unmap(vaddr);
 89
 90		scatterwalk_advance(walk, len_this_page);
 91
 92		if (nbytes == len_this_page)
 93			break;
 94
 95		buf += len_this_page;
 96		nbytes -= len_this_page;
 97
 98		scatterwalk_pagedone(walk, out, 1);
 99	}
100}
101EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
102
103void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
104			      unsigned int start, unsigned int nbytes, int out)
105{
106	struct scatter_walk walk;
107	unsigned int offset = 0;
108
109	if (!nbytes)
110		return;
111
112	for (;;) {
113		scatterwalk_start(&walk, sg);
114
115		if (start < offset + sg->length)
116			break;
117
118		offset += sg->length;
119		sg = scatterwalk_sg_next(sg);
120	}
121
122	scatterwalk_advance(&walk, start - offset);
123	scatterwalk_copychunks(buf, &walk, nbytes, out);
124	scatterwalk_done(&walk, out, 0);
125}
126EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);