scatterwalk.c revision 8fc8598e61f6f384f3eaf1d9b09500c12af47b37 
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#include "kmap_types.h"
17
18#include <linux/kernel.h>
19#include <linux/mm.h>
20#include <linux/pagemap.h>
21#include <linux/highmem.h>
22#include <asm/scatterlist.h>
23#include "internal.h"
24#include "scatterwalk.h"
25
26enum km_type crypto_km_types[] = {
27	KM_USER0,
28	KM_USER1,
29	KM_SOFTIRQ0,
30	KM_SOFTIRQ1,
31};
32
33void *scatterwalk_whichbuf(struct scatter_walk *walk, unsigned int nbytes, void *scratch)
34{
35	if (nbytes <= walk->len_this_page &&
36	    (((unsigned long)walk->data) & (PAGE_CACHE_SIZE - 1)) + nbytes <=
37	    PAGE_CACHE_SIZE)
38		return walk->data;
39	else
40		return scratch;
41}
42
43static void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
44{
45	if (out)
46		memcpy(sgdata, buf, nbytes);
47	else
48		memcpy(buf, sgdata, nbytes);
49}
50
51void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
52{
53	unsigned int rest_of_page;
54
55	walk->sg = sg;
56
57	walk->page = sg->page;
58	walk->len_this_segment = sg->length;
59
60	rest_of_page = PAGE_CACHE_SIZE - (sg->offset & (PAGE_CACHE_SIZE - 1));
61	walk->len_this_page = min(sg->length, rest_of_page);
62	walk->offset = sg->offset;
63}
64
65void scatterwalk_map(struct scatter_walk *walk, int out)
66{
67	walk->data = crypto_kmap(walk->page, out) + walk->offset;
68}
69
70static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
71				 unsigned int more)
72{
73	/* walk->data may be pointing the first byte of the next page;
74	   however, we know we transfered at least one byte.  So,
75	   walk->data - 1 will be a virtual address in the mapped page. */
76
77	if (out)
78		flush_dcache_page(walk->page);
79
80	if (more) {
81		walk->len_this_segment -= walk->len_this_page;
82
83		if (walk->len_this_segment) {
84			walk->page++;
85			walk->len_this_page = min(walk->len_this_segment,
86						  (unsigned)PAGE_CACHE_SIZE);
87			walk->offset = 0;
88		}
89		else
90			scatterwalk_start(walk, sg_next(walk->sg));
91	}
92}
93
94void scatterwalk_done(struct scatter_walk *walk, int out, int more)
95{
96	crypto_kunmap(walk->data, out);
97	if (walk->len_this_page == 0 || !more)
98		scatterwalk_pagedone(walk, out, more);
99}
100
101/*
102 * Do not call this unless the total length of all of the fragments
103 * has been verified as multiple of the block size.
104 */
105int scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
106			   size_t nbytes, int out)
107{
108	if (buf != walk->data) {
109		while (nbytes > walk->len_this_page) {
110			memcpy_dir(buf, walk->data, walk->len_this_page, out);
111			buf += walk->len_this_page;
112			nbytes -= walk->len_this_page;
113
114			crypto_kunmap(walk->data, out);
115			scatterwalk_pagedone(walk, out, 1);
116			scatterwalk_map(walk, out);
117		}
118
119		memcpy_dir(buf, walk->data, nbytes, out);
120	}
121
122	walk->offset += nbytes;
123	walk->len_this_page -= nbytes;
124	walk->len_this_segment -= nbytes;
125	return 0;
126}
127