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Linux/fs/udf/symlink.c

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  1 /*
  2  * symlink.c
  3  *
  4  * PURPOSE
  5  *      Symlink handling routines for the OSTA-UDF(tm) filesystem.
  6  *
  7  * COPYRIGHT
  8  *      This file is distributed under the terms of the GNU General Public
  9  *      License (GPL). Copies of the GPL can be obtained from:
 10  *              ftp://prep.ai.mit.edu/pub/gnu/GPL
 11  *      Each contributing author retains all rights to their own work.
 12  *
 13  *  (C) 1998-2001 Ben Fennema
 14  *  (C) 1999 Stelias Computing Inc
 15  *
 16  * HISTORY
 17  *
 18  *  04/16/99 blf  Created.
 19  *
 20  */
 21 
 22 #include "udfdecl.h"
 23 #include <linux/uaccess.h>
 24 #include <linux/errno.h>
 25 #include <linux/fs.h>
 26 #include <linux/time.h>
 27 #include <linux/mm.h>
 28 #include <linux/stat.h>
 29 #include <linux/pagemap.h>
 30 #include <linux/buffer_head.h>
 31 #include "udf_i.h"
 32 
 33 static int udf_pc_to_char(struct super_block *sb, unsigned char *from,
 34                           int fromlen, unsigned char *to, int tolen)
 35 {
 36         struct pathComponent *pc;
 37         int elen = 0;
 38         int comp_len;
 39         unsigned char *p = to;
 40 
 41         /* Reserve one byte for terminating \0 */
 42         tolen--;
 43         while (elen < fromlen) {
 44                 pc = (struct pathComponent *)(from + elen);
 45                 elen += sizeof(struct pathComponent);
 46                 switch (pc->componentType) {
 47                 case 1:
 48                         /*
 49                          * Symlink points to some place which should be agreed
 50                          * upon between originator and receiver of the media. Ignore.
 51                          */
 52                         if (pc->lengthComponentIdent > 0) {
 53                                 elen += pc->lengthComponentIdent;
 54                                 break;
 55                         }
 56                         /* Fall through */
 57                 case 2:
 58                         if (tolen == 0)
 59                                 return -ENAMETOOLONG;
 60                         p = to;
 61                         *p++ = '/';
 62                         tolen--;
 63                         break;
 64                 case 3:
 65                         if (tolen < 3)
 66                                 return -ENAMETOOLONG;
 67                         memcpy(p, "../", 3);
 68                         p += 3;
 69                         tolen -= 3;
 70                         break;
 71                 case 4:
 72                         if (tolen < 2)
 73                                 return -ENAMETOOLONG;
 74                         memcpy(p, "./", 2);
 75                         p += 2;
 76                         tolen -= 2;
 77                         /* that would be . - just ignore */
 78                         break;
 79                 case 5:
 80                         elen += pc->lengthComponentIdent;
 81                         if (elen > fromlen)
 82                                 return -EIO;
 83                         comp_len = udf_get_filename(sb, pc->componentIdent,
 84                                                     pc->lengthComponentIdent,
 85                                                     p, tolen);
 86                         p += comp_len;
 87                         tolen -= comp_len;
 88                         if (tolen == 0)
 89                                 return -ENAMETOOLONG;
 90                         *p++ = '/';
 91                         tolen--;
 92                         break;
 93                 }
 94         }
 95         if (p > to + 1)
 96                 p[-1] = '\0';
 97         else
 98                 p[0] = '\0';
 99         return 0;
100 }
101 
102 static int udf_symlink_filler(struct file *file, struct page *page)
103 {
104         struct inode *inode = page->mapping->host;
105         struct buffer_head *bh = NULL;
106         unsigned char *symlink;
107         int err;
108         unsigned char *p = kmap(page);
109         struct udf_inode_info *iinfo;
110         uint32_t pos;
111 
112         /* We don't support symlinks longer than one block */
113         if (inode->i_size > inode->i_sb->s_blocksize) {
114                 err = -ENAMETOOLONG;
115                 goto out_unmap;
116         }
117 
118         iinfo = UDF_I(inode);
119         pos = udf_block_map(inode, 0);
120 
121         down_read(&iinfo->i_data_sem);
122         if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
123                 symlink = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
124         } else {
125                 bh = sb_bread(inode->i_sb, pos);
126 
127                 if (!bh) {
128                         err = -EIO;
129                         goto out_unlock_inode;
130                 }
131 
132                 symlink = bh->b_data;
133         }
134 
135         err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE);
136         brelse(bh);
137         if (err)
138                 goto out_unlock_inode;
139 
140         up_read(&iinfo->i_data_sem);
141         SetPageUptodate(page);
142         kunmap(page);
143         unlock_page(page);
144         return 0;
145 
146 out_unlock_inode:
147         up_read(&iinfo->i_data_sem);
148         SetPageError(page);
149 out_unmap:
150         kunmap(page);
151         unlock_page(page);
152         return err;
153 }
154 
155 /*
156  * symlinks can't do much...
157  */
158 const struct address_space_operations udf_symlink_aops = {
159         .readpage               = udf_symlink_filler,
160 };
161 

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