1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Cryptographic API.
4  *
5  * Cipher operations.
6  *
7  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
8  *               2002 Adam J. Richter <adam@yggdrasil.com>
9  *               2004 Jean-Luc Cooke <jlcooke@certainkey.com>
10  */
11 
12 #include <crypto/scatterwalk.h>
13 #include <linux/kernel.h>
14 #include <linux/mm.h>
15 #include <linux/module.h>
16 #include <linux/scatterlist.h>
17 
memcpy_dir(void * buf,void * sgdata,size_t nbytes,int out)18 static inline void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
19 {
20 	void *src = out ? buf : sgdata;
21 	void *dst = out ? sgdata : buf;
22 
23 	memcpy(dst, src, nbytes);
24 }
25 
scatterwalk_copychunks(void * buf,struct scatter_walk * walk,size_t nbytes,int out)26 void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
27 			    size_t nbytes, int out)
28 {
29 	for (;;) {
30 		unsigned int len_this_page = scatterwalk_pagelen(walk);
31 		u8 *vaddr;
32 
33 		if (len_this_page > nbytes)
34 			len_this_page = nbytes;
35 
36 		if (out != 2) {
37 			vaddr = scatterwalk_map(walk);
38 			memcpy_dir(buf, vaddr, len_this_page, out);
39 			scatterwalk_unmap(vaddr);
40 		}
41 
42 		scatterwalk_advance(walk, len_this_page);
43 
44 		if (nbytes == len_this_page)
45 			break;
46 
47 		buf += len_this_page;
48 		nbytes -= len_this_page;
49 
50 		scatterwalk_pagedone(walk, out & 1, 1);
51 	}
52 }
53 EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
54 
scatterwalk_map_and_copy(void * buf,struct scatterlist * sg,unsigned int start,unsigned int nbytes,int out)55 void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
56 			      unsigned int start, unsigned int nbytes, int out)
57 {
58 	struct scatter_walk walk;
59 	struct scatterlist tmp[2];
60 
61 	if (!nbytes)
62 		return;
63 
64 	sg = scatterwalk_ffwd(tmp, sg, start);
65 
66 	scatterwalk_start(&walk, sg);
67 	scatterwalk_copychunks(buf, &walk, nbytes, out);
68 	scatterwalk_done(&walk, out, 0);
69 }
70 EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
71 
scatterwalk_ffwd(struct scatterlist dst[2],struct scatterlist * src,unsigned int len)72 struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
73 				     struct scatterlist *src,
74 				     unsigned int len)
75 {
76 	for (;;) {
77 		if (!len)
78 			return src;
79 
80 		if (src->length > len)
81 			break;
82 
83 		len -= src->length;
84 		src = sg_next(src);
85 	}
86 
87 	sg_init_table(dst, 2);
88 	sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
89 	scatterwalk_crypto_chain(dst, sg_next(src), 2);
90 
91 	return dst;
92 }
93 EXPORT_SYMBOL_GPL(scatterwalk_ffwd);
94