fs/udf/symlink.c

   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 <asm/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 };