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		/* Test ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE first as
58		 * PageSlab cannot be optimised away per se due to
59		 * use of volatile pointer.
60		 */
61		if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE && !PageSlab(page))
62			flush_dcache_page(page);
63	}
64
65	if (more) {
66		walk->offset += PAGE_SIZE - 1;
67		walk->offset &= PAGE_MASK;
68		if (walk->offset >= walk->sg->offset + walk->sg->length)
69			scatterwalk_start(walk, sg_next(walk->sg));
70	}
71}
72
73void scatterwalk_done(struct scatter_walk *walk, int out, int more)
74{
75	if (!(scatterwalk_pagelen(walk) & (PAGE_SIZE - 1)) || !more)
76		scatterwalk_pagedone(walk, out, more);
77}
78EXPORT_SYMBOL_GPL(scatterwalk_done);
79
80void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
81			    size_t nbytes, int out)
82{
83	for (;;) {
84		unsigned int len_this_page = scatterwalk_pagelen(walk);
85		u8 *vaddr;
86
87		if (len_this_page > nbytes)
88			len_this_page = nbytes;
89
90		vaddr = scatterwalk_map(walk);
91		memcpy_dir(buf, vaddr, len_this_page, out);
92		scatterwalk_unmap(vaddr);
93
94		scatterwalk_advance(walk, len_this_page);
95
96		if (nbytes == len_this_page)
97			break;
98
99		buf += len_this_page;
100		nbytes -= len_this_page;
101
102		scatterwalk_pagedone(walk, out, 1);
103	}
104}
105EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
106
107void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
108			      unsigned int start, unsigned int nbytes, int out)
109{
110	struct scatter_walk walk;
111	struct scatterlist tmp[2];
112
113	if (!nbytes)
114		return;
115
116	sg = scatterwalk_ffwd(tmp, sg, start);
117
118	if (sg_page(sg) == virt_to_page(buf) &&
119	    sg->offset == offset_in_page(buf))
120		return;
121
122	scatterwalk_start(&walk, sg);
123	scatterwalk_copychunks(buf, &walk, nbytes, out);
124	scatterwalk_done(&walk, out, 0);
125}
126EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
127
128int scatterwalk_bytes_sglen(struct scatterlist *sg, int num_bytes)
129{
130	int offset = 0, n = 0;
131
132	/* num_bytes is too small */
133	if (num_bytes < sg->length)
134		return -1;
135
136	do {
137		offset += sg->length;
138		n++;
139		sg = sg_next(sg);
140
141		/* num_bytes is too large */
142		if (unlikely(!sg && (num_bytes < offset)))
143			return -1;
144	} while (sg && (num_bytes > offset));
145
146	return n;
147}
148EXPORT_SYMBOL_GPL(scatterwalk_bytes_sglen);
149
150struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
151				     struct scatterlist *src,
152				     unsigned int len)
153{
154	for (;;) {
155		if (!len)
156			return src;
157
158		if (src->length > len)
159			break;
160
161		len -= src->length;
162		src = sg_next(src);
163	}
164
165	sg_init_table(dst, 2);
166	sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
167	scatterwalk_crypto_chain(dst, sg_next(src), 0, 2);
168
169	return dst;
170}
171EXPORT_SYMBOL_GPL(scatterwalk_ffwd);
172