1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * QNX4 file system, Linux implementation.
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Version : 0.2.1
6*4882a593Smuzhiyun *
7*4882a593Smuzhiyun * Using parts of the xiafs filesystem.
8*4882a593Smuzhiyun *
9*4882a593Smuzhiyun * History :
10*4882a593Smuzhiyun *
11*4882a593Smuzhiyun * 28-05-1998 by Richard Frowijn : first release.
12*4882a593Smuzhiyun * 20-06-1998 by Frank Denis : Linux 2.1.99+ & dcache support.
13*4882a593Smuzhiyun */
14*4882a593Smuzhiyun
15*4882a593Smuzhiyun #include <linux/buffer_head.h>
16*4882a593Smuzhiyun #include "qnx4.h"
17*4882a593Smuzhiyun
18*4882a593Smuzhiyun /*
19*4882a593Smuzhiyun * A qnx4 directory entry is an inode entry or link info
20*4882a593Smuzhiyun * depending on the status field in the last byte. The
21*4882a593Smuzhiyun * first byte is where the name start either way, and a
22*4882a593Smuzhiyun * zero means it's empty.
23*4882a593Smuzhiyun *
24*4882a593Smuzhiyun * Also, due to a bug in gcc, we don't want to use the
25*4882a593Smuzhiyun * real (differently sized) name arrays in the inode and
26*4882a593Smuzhiyun * link entries, but always the 'de_name[]' one in the
27*4882a593Smuzhiyun * fake struct entry.
28*4882a593Smuzhiyun *
29*4882a593Smuzhiyun * See
30*4882a593Smuzhiyun *
31*4882a593Smuzhiyun * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
32*4882a593Smuzhiyun *
33*4882a593Smuzhiyun * for details, but basically gcc will take the size of the
34*4882a593Smuzhiyun * 'name' array from one of the used union entries randomly.
35*4882a593Smuzhiyun *
36*4882a593Smuzhiyun * This use of 'de_name[]' (48 bytes) avoids the false positive
37*4882a593Smuzhiyun * warnings that would happen if gcc decides to use 'inode.di_name'
38*4882a593Smuzhiyun * (16 bytes) even when the pointer and size were to come from
39*4882a593Smuzhiyun * 'link.dl_name' (48 bytes).
40*4882a593Smuzhiyun *
41*4882a593Smuzhiyun * In all cases the actual name pointer itself is the same, it's
42*4882a593Smuzhiyun * only the gcc internal 'what is the size of this field' logic
43*4882a593Smuzhiyun * that can get confused.
44*4882a593Smuzhiyun */
45*4882a593Smuzhiyun union qnx4_directory_entry {
46*4882a593Smuzhiyun struct {
47*4882a593Smuzhiyun const char de_name[48];
48*4882a593Smuzhiyun u8 de_pad[15];
49*4882a593Smuzhiyun u8 de_status;
50*4882a593Smuzhiyun };
51*4882a593Smuzhiyun struct qnx4_inode_entry inode;
52*4882a593Smuzhiyun struct qnx4_link_info link;
53*4882a593Smuzhiyun };
54*4882a593Smuzhiyun
qnx4_readdir(struct file * file,struct dir_context * ctx)55*4882a593Smuzhiyun static int qnx4_readdir(struct file *file, struct dir_context *ctx)
56*4882a593Smuzhiyun {
57*4882a593Smuzhiyun struct inode *inode = file_inode(file);
58*4882a593Smuzhiyun unsigned int offset;
59*4882a593Smuzhiyun struct buffer_head *bh;
60*4882a593Smuzhiyun unsigned long blknum;
61*4882a593Smuzhiyun int ix, ino;
62*4882a593Smuzhiyun int size;
63*4882a593Smuzhiyun
64*4882a593Smuzhiyun QNX4DEBUG((KERN_INFO "qnx4_readdir:i_size = %ld\n", (long) inode->i_size));
65*4882a593Smuzhiyun QNX4DEBUG((KERN_INFO "pos = %ld\n", (long) ctx->pos));
66*4882a593Smuzhiyun
67*4882a593Smuzhiyun while (ctx->pos < inode->i_size) {
68*4882a593Smuzhiyun blknum = qnx4_block_map(inode, ctx->pos >> QNX4_BLOCK_SIZE_BITS);
69*4882a593Smuzhiyun bh = sb_bread(inode->i_sb, blknum);
70*4882a593Smuzhiyun if (bh == NULL) {
71*4882a593Smuzhiyun printk(KERN_ERR "qnx4_readdir: bread failed (%ld)\n", blknum);
72*4882a593Smuzhiyun return 0;
73*4882a593Smuzhiyun }
74*4882a593Smuzhiyun ix = (ctx->pos >> QNX4_DIR_ENTRY_SIZE_BITS) % QNX4_INODES_PER_BLOCK;
75*4882a593Smuzhiyun for (; ix < QNX4_INODES_PER_BLOCK; ix++, ctx->pos += QNX4_DIR_ENTRY_SIZE) {
76*4882a593Smuzhiyun union qnx4_directory_entry *de;
77*4882a593Smuzhiyun
78*4882a593Smuzhiyun offset = ix * QNX4_DIR_ENTRY_SIZE;
79*4882a593Smuzhiyun de = (union qnx4_directory_entry *) (bh->b_data + offset);
80*4882a593Smuzhiyun
81*4882a593Smuzhiyun if (!de->de_name[0])
82*4882a593Smuzhiyun continue;
83*4882a593Smuzhiyun if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
84*4882a593Smuzhiyun continue;
85*4882a593Smuzhiyun if (!(de->de_status & QNX4_FILE_LINK)) {
86*4882a593Smuzhiyun size = sizeof(de->inode.di_fname);
87*4882a593Smuzhiyun ino = blknum * QNX4_INODES_PER_BLOCK + ix - 1;
88*4882a593Smuzhiyun } else {
89*4882a593Smuzhiyun size = sizeof(de->link.dl_fname);
90*4882a593Smuzhiyun ino = ( le32_to_cpu(de->link.dl_inode_blk) - 1 ) *
91*4882a593Smuzhiyun QNX4_INODES_PER_BLOCK +
92*4882a593Smuzhiyun de->link.dl_inode_ndx;
93*4882a593Smuzhiyun }
94*4882a593Smuzhiyun size = strnlen(de->de_name, size);
95*4882a593Smuzhiyun QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, name));
96*4882a593Smuzhiyun if (!dir_emit(ctx, de->de_name, size, ino, DT_UNKNOWN)) {
97*4882a593Smuzhiyun brelse(bh);
98*4882a593Smuzhiyun return 0;
99*4882a593Smuzhiyun }
100*4882a593Smuzhiyun }
101*4882a593Smuzhiyun brelse(bh);
102*4882a593Smuzhiyun }
103*4882a593Smuzhiyun return 0;
104*4882a593Smuzhiyun }
105*4882a593Smuzhiyun
106*4882a593Smuzhiyun const struct file_operations qnx4_dir_operations =
107*4882a593Smuzhiyun {
108*4882a593Smuzhiyun .llseek = generic_file_llseek,
109*4882a593Smuzhiyun .read = generic_read_dir,
110*4882a593Smuzhiyun .iterate_shared = qnx4_readdir,
111*4882a593Smuzhiyun .fsync = generic_file_fsync,
112*4882a593Smuzhiyun };
113*4882a593Smuzhiyun
114*4882a593Smuzhiyun const struct inode_operations qnx4_dir_inode_operations =
115*4882a593Smuzhiyun {
116*4882a593Smuzhiyun .lookup = qnx4_lookup,
117*4882a593Smuzhiyun };
118