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Linux kernel mirror (for testing)
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linux
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/drivers/staging/erofs/dir.c
4 *
5 * Copyright (C) 2017-2018 HUAWEI, Inc.
6 * http://www.huawei.com/
7 * Created by Gao Xiang <gaoxiang25@huawei.com>
8 *
9 * This file is subject to the terms and conditions of the GNU General Public
10 * License. See the file COPYING in the main directory of the Linux
11 * distribution for more details.
12 */
13#include "internal.h"
14
15static const unsigned char erofs_filetype_table[EROFS_FT_MAX] = {
16 [EROFS_FT_UNKNOWN] = DT_UNKNOWN,
17 [EROFS_FT_REG_FILE] = DT_REG,
18 [EROFS_FT_DIR] = DT_DIR,
19 [EROFS_FT_CHRDEV] = DT_CHR,
20 [EROFS_FT_BLKDEV] = DT_BLK,
21 [EROFS_FT_FIFO] = DT_FIFO,
22 [EROFS_FT_SOCK] = DT_SOCK,
23 [EROFS_FT_SYMLINK] = DT_LNK,
24};
25
26static void debug_one_dentry(unsigned char d_type, const char *de_name,
27 unsigned int de_namelen)
28{
29#ifdef CONFIG_EROFS_FS_DEBUG
30 /* since the on-disk name could not have the trailing '\0' */
31 unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
32
33 memcpy(dbg_namebuf, de_name, de_namelen);
34 dbg_namebuf[de_namelen] = '\0';
35
36 debugln("found dirent %s de_len %u d_type %d", dbg_namebuf,
37 de_namelen, d_type);
38#endif
39}
40
41static int erofs_fill_dentries(struct dir_context *ctx,
42 void *dentry_blk, unsigned int *ofs,
43 unsigned int nameoff, unsigned int maxsize)
44{
45 struct erofs_dirent *de = dentry_blk;
46 const struct erofs_dirent *end = dentry_blk + nameoff;
47
48 de = dentry_blk + *ofs;
49 while (de < end) {
50 const char *de_name;
51 unsigned int de_namelen;
52 unsigned char d_type;
53
54 if (de->file_type < EROFS_FT_MAX)
55 d_type = erofs_filetype_table[de->file_type];
56 else
57 d_type = DT_UNKNOWN;
58
59 nameoff = le16_to_cpu(de->nameoff);
60 de_name = (char *)dentry_blk + nameoff;
61
62 /* the last dirent in the block? */
63 if (de + 1 >= end)
64 de_namelen = strnlen(de_name, maxsize - nameoff);
65 else
66 de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
67
68 /* a corrupted entry is found */
69 if (unlikely(nameoff + de_namelen > maxsize ||
70 de_namelen > EROFS_NAME_LEN)) {
71 DBG_BUGON(1);
72 return -EIO;
73 }
74
75 debug_one_dentry(d_type, de_name, de_namelen);
76 if (!dir_emit(ctx, de_name, de_namelen,
77 le64_to_cpu(de->nid), d_type))
78 /* stopped by some reason */
79 return 1;
80 ++de;
81 *ofs += sizeof(struct erofs_dirent);
82 }
83 *ofs = maxsize;
84 return 0;
85}
86
87static int erofs_readdir(struct file *f, struct dir_context *ctx)
88{
89 struct inode *dir = file_inode(f);
90 struct address_space *mapping = dir->i_mapping;
91 const size_t dirsize = i_size_read(dir);
92 unsigned int i = ctx->pos / EROFS_BLKSIZ;
93 unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
94 int err = 0;
95 bool initial = true;
96
97 while (ctx->pos < dirsize) {
98 struct page *dentry_page;
99 struct erofs_dirent *de;
100 unsigned int nameoff, maxsize;
101
102 dentry_page = read_mapping_page(mapping, i, NULL);
103 if (IS_ERR(dentry_page))
104 continue;
105
106 de = (struct erofs_dirent *)kmap(dentry_page);
107
108 nameoff = le16_to_cpu(de->nameoff);
109
110 if (unlikely(nameoff < sizeof(struct erofs_dirent) ||
111 nameoff >= PAGE_SIZE)) {
112 errln("%s, invalid de[0].nameoff %u",
113 __func__, nameoff);
114
115 err = -EIO;
116 goto skip_this;
117 }
118
119 maxsize = min_t(unsigned int,
120 dirsize - ctx->pos + ofs, PAGE_SIZE);
121
122 /* search dirents at the arbitrary position */
123 if (unlikely(initial)) {
124 initial = false;
125
126 ofs = roundup(ofs, sizeof(struct erofs_dirent));
127 if (unlikely(ofs >= nameoff))
128 goto skip_this;
129 }
130
131 err = erofs_fill_dentries(ctx, de, &ofs, nameoff, maxsize);
132skip_this:
133 kunmap(dentry_page);
134
135 put_page(dentry_page);
136
137 ctx->pos = blknr_to_addr(i) + ofs;
138
139 if (unlikely(err))
140 break;
141 ++i;
142 ofs = 0;
143 }
144 return err < 0 ? err : 0;
145}
146
147const struct file_operations erofs_dir_fops = {
148 .llseek = generic_file_llseek,
149 .read = generic_read_dir,
150 .iterate_shared = erofs_readdir,
151};
152