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[linux-3.10.git] / crypto / scatterwalk.c
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                 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
69 void 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 }
74 EXPORT_SYMBOL_GPL(scatterwalk_done);
75
76 void 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 }
101 EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
102
103 void 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 }
126 EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);