Root/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
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);
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 = scatterwalk_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

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