1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * dir.c
4  *
5  * Copyright (c) 1999 Al Smith
6  */
7 
8 #include <linux/buffer_head.h>
9 #include "efs.h"
10 
11 static int efs_readdir(struct file *, struct dir_context *);
12 
13 const struct file_operations efs_dir_operations = {
14 	.llseek		= generic_file_llseek,
15 	.read		= generic_read_dir,
16 	.iterate_shared	= efs_readdir,
17 };
18 
19 const struct inode_operations efs_dir_inode_operations = {
20 	.lookup		= efs_lookup,
21 };
22 
efs_readdir(struct file * file,struct dir_context * ctx)23 static int efs_readdir(struct file *file, struct dir_context *ctx)
24 {
25 	struct inode *inode = file_inode(file);
26 	efs_block_t		block;
27 	int			slot;
28 
29 	if (inode->i_size & (EFS_DIRBSIZE-1))
30 		pr_warn("%s(): directory size not a multiple of EFS_DIRBSIZE\n",
31 			__func__);
32 
33 	/* work out where this entry can be found */
34 	block = ctx->pos >> EFS_DIRBSIZE_BITS;
35 
36 	/* each block contains at most 256 slots */
37 	slot  = ctx->pos & 0xff;
38 
39 	/* look at all blocks */
40 	while (block < inode->i_blocks) {
41 		struct efs_dir		*dirblock;
42 		struct buffer_head *bh;
43 
44 		/* read the dir block */
45 		bh = sb_bread(inode->i_sb, efs_bmap(inode, block));
46 
47 		if (!bh) {
48 			pr_err("%s(): failed to read dir block %d\n",
49 			       __func__, block);
50 			break;
51 		}
52 
53 		dirblock = (struct efs_dir *) bh->b_data;
54 
55 		if (be16_to_cpu(dirblock->magic) != EFS_DIRBLK_MAGIC) {
56 			pr_err("%s(): invalid directory block\n", __func__);
57 			brelse(bh);
58 			break;
59 		}
60 
61 		for (; slot < dirblock->slots; slot++) {
62 			struct efs_dentry *dirslot;
63 			efs_ino_t inodenum;
64 			const char *nameptr;
65 			int namelen;
66 
67 			if (dirblock->space[slot] == 0)
68 				continue;
69 
70 			dirslot  = (struct efs_dentry *) (((char *) bh->b_data) + EFS_SLOTAT(dirblock, slot));
71 
72 			inodenum = be32_to_cpu(dirslot->inode);
73 			namelen  = dirslot->namelen;
74 			nameptr  = dirslot->name;
75 			pr_debug("%s(): block %d slot %d/%d: inode %u, name \"%s\", namelen %u\n",
76 				 __func__, block, slot, dirblock->slots-1,
77 				 inodenum, nameptr, namelen);
78 			if (!namelen)
79 				continue;
80 			/* found the next entry */
81 			ctx->pos = (block << EFS_DIRBSIZE_BITS) | slot;
82 
83 			/* sanity check */
84 			if (nameptr - (char *) dirblock + namelen > EFS_DIRBSIZE) {
85 				pr_warn("directory entry %d exceeds directory block\n",
86 					slot);
87 				continue;
88 			}
89 
90 			/* copy filename and data in dirslot */
91 			if (!dir_emit(ctx, nameptr, namelen, inodenum, DT_UNKNOWN)) {
92 				brelse(bh);
93 				return 0;
94 			}
95 		}
96 		brelse(bh);
97 
98 		slot = 0;
99 		block++;
100 	}
101 	ctx->pos = (block << EFS_DIRBSIZE_BITS) | slot;
102 	return 0;
103 }
104