xref: /linux/crypto/scatterwalk.c (revision b85d45947951d23cb22d90caecf4c1eb81342c96)
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 
25 static 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 
33 void 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 }
41 EXPORT_SYMBOL_GPL(scatterwalk_start);
42 
43 void *scatterwalk_map(struct scatter_walk *walk)
44 {
45 	return kmap_atomic(scatterwalk_page(walk)) +
46 	       offset_in_page(walk->offset);
47 }
48 EXPORT_SYMBOL_GPL(scatterwalk_map);
49 
50 static 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 
73 void 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 }
78 EXPORT_SYMBOL_GPL(scatterwalk_done);
79 
80 void 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 }
105 EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
106 
107 void 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 }
126 EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
127 
128 int 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 }
148 EXPORT_SYMBOL_GPL(scatterwalk_bytes_sglen);
149 
150 struct 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 }
171 EXPORT_SYMBOL_GPL(scatterwalk_ffwd);
172