1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * QNX4 file system, Linux implementation.
4  *
5  * Version : 0.2.1
6  *
7  * Using parts of the xiafs filesystem.
8  *
9  * History :
10  *
11  * 28-05-1998 by Richard Frowijn : first release.
12  * 20-06-1998 by Frank Denis : Linux 2.1.99+ & dcache support.
13  */
14 
15 #include <linux/buffer_head.h>
16 #include "qnx4.h"
17 
18 /*
19  * A qnx4 directory entry is an inode entry or link info
20  * depending on the status field in the last byte. The
21  * first byte is where the name start either way, and a
22  * zero means it's empty.
23  *
24  * Also, due to a bug in gcc, we don't want to use the
25  * real (differently sized) name arrays in the inode and
26  * link entries, but always the 'de_name[]' one in the
27  * fake struct entry.
28  *
29  * See
30  *
31  *   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
32  *
33  * for details, but basically gcc will take the size of the
34  * 'name' array from one of the used union entries randomly.
35  *
36  * This use of 'de_name[]' (48 bytes) avoids the false positive
37  * warnings that would happen if gcc decides to use 'inode.di_name'
38  * (16 bytes) even when the pointer and size were to come from
39  * 'link.dl_name' (48 bytes).
40  *
41  * In all cases the actual name pointer itself is the same, it's
42  * only the gcc internal 'what is the size of this field' logic
43  * that can get confused.
44  */
45 union qnx4_directory_entry {
46 	struct {
47 		const char de_name[48];
48 		u8 de_pad[15];
49 		u8 de_status;
50 	};
51 	struct qnx4_inode_entry inode;
52 	struct qnx4_link_info link;
53 };
54 
qnx4_readdir(struct file * file,struct dir_context * ctx)55 static int qnx4_readdir(struct file *file, struct dir_context *ctx)
56 {
57 	struct inode *inode = file_inode(file);
58 	unsigned int offset;
59 	struct buffer_head *bh;
60 	unsigned long blknum;
61 	int ix, ino;
62 	int size;
63 
64 	QNX4DEBUG((KERN_INFO "qnx4_readdir:i_size = %ld\n", (long) inode->i_size));
65 	QNX4DEBUG((KERN_INFO "pos                 = %ld\n", (long) ctx->pos));
66 
67 	while (ctx->pos < inode->i_size) {
68 		blknum = qnx4_block_map(inode, ctx->pos >> QNX4_BLOCK_SIZE_BITS);
69 		bh = sb_bread(inode->i_sb, blknum);
70 		if (bh == NULL) {
71 			printk(KERN_ERR "qnx4_readdir: bread failed (%ld)\n", blknum);
72 			return 0;
73 		}
74 		ix = (ctx->pos >> QNX4_DIR_ENTRY_SIZE_BITS) % QNX4_INODES_PER_BLOCK;
75 		for (; ix < QNX4_INODES_PER_BLOCK; ix++, ctx->pos += QNX4_DIR_ENTRY_SIZE) {
76 			union qnx4_directory_entry *de;
77 
78 			offset = ix * QNX4_DIR_ENTRY_SIZE;
79 			de = (union qnx4_directory_entry *) (bh->b_data + offset);
80 
81 			if (!de->de_name[0])
82 				continue;
83 			if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
84 				continue;
85 			if (!(de->de_status & QNX4_FILE_LINK)) {
86 				size = sizeof(de->inode.di_fname);
87 				ino = blknum * QNX4_INODES_PER_BLOCK + ix - 1;
88 			} else {
89 				size = sizeof(de->link.dl_fname);
90 				ino = ( le32_to_cpu(de->link.dl_inode_blk) - 1 ) *
91 					QNX4_INODES_PER_BLOCK +
92 					de->link.dl_inode_ndx;
93 			}
94 			size = strnlen(de->de_name, size);
95 			QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, name));
96 			if (!dir_emit(ctx, de->de_name, size, ino, DT_UNKNOWN)) {
97 				brelse(bh);
98 				return 0;
99 			}
100 		}
101 		brelse(bh);
102 	}
103 	return 0;
104 }
105 
106 const struct file_operations qnx4_dir_operations =
107 {
108 	.llseek		= generic_file_llseek,
109 	.read		= generic_read_dir,
110 	.iterate_shared	= qnx4_readdir,
111 	.fsync		= generic_file_fsync,
112 };
113 
114 const struct inode_operations qnx4_dir_inode_operations =
115 {
116 	.lookup		= qnx4_lookup,
117 };
118