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                 switch (pc->componentType) {
  46                 case 1:
  47                         /*
  48                          * Symlink points to some place which should be agreed
  49                          * upon between originator and receiver of the media. Ignore.
  50                          */
  51                         if (pc->lengthComponentIdent > 0)
  52                                 break;
  53                         /* Fall through */
  54                 case 2:
  55                         if (tolen == 0)
  56                                 return -ENAMETOOLONG;
  57                         p = to;
  58                         *p++ = '/';
  59                         tolen--;
  60                         break;
  61                 case 3:
  62                         if (tolen < 3)
  63                                 return -ENAMETOOLONG;
  64                         memcpy(p, "../", 3);
  65                         p += 3;
  66                         tolen -= 3;
  67                         break;
  68                 case 4:
  69                         if (tolen < 2)
  70                                 return -ENAMETOOLONG;
  71                         memcpy(p, "./", 2);
  72                         p += 2;
  73                         tolen -= 2;
  74                         /* that would be . - just ignore */
  75                         break;
  76                 case 5:
  77                         comp_len = udf_get_filename(sb, pc->componentIdent,
  78                                                     pc->lengthComponentIdent,
  79                                                     p, tolen);
  80                         p += comp_len;
  81                         tolen -= comp_len;
  82                         if (tolen == 0)
  83                                 return -ENAMETOOLONG;
  84                         *p++ = '/';
  85                         tolen--;
  86                         break;
  87                 }
  88                 elen += sizeof(struct pathComponent) + pc->lengthComponentIdent;
  89         }
  90         if (p > to + 1)
  91                 p[-1] = '\0';
  92         else
  93                 p[0] = '\0';
  94         return 0;
  95 }
  96
  97 static int udf_symlink_filler(struct file *file, struct page *page)
  98 {
  99         struct inode *inode = page->mapping->host;
 100         struct buffer_head *bh = NULL;
 101         unsigned char *symlink;
 102         int err;
 103         unsigned char *p = kmap(page);
 104         struct udf_inode_info *iinfo;
 105         uint32_t pos;
 106
 107         /* We don't support symlinks longer than one block */
 108         if (inode->i_size > inode->i_sb->s_blocksize) {
 109                 err = -ENAMETOOLONG;
 110                 goto out_unmap;
 111         }
 112
 113         iinfo = UDF_I(inode);
 114         pos = udf_block_map(inode, 0);
 115
 116         down_read(&iinfo->i_data_sem);
 117         if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
 118                 symlink = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
 119         } else {
 120                 bh = sb_bread(inode->i_sb, pos);
 121
 122                 if (!bh) {
 123                         err = -EIO;
 124                         goto out_unlock_inode;
 125                 }
 126
 127                 symlink = bh->b_data;
 128         }
 129
 130         err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE);
 131         brelse(bh);
 132         if (err)
 133                 goto out_unlock_inode;
 134
 135         up_read(&iinfo->i_data_sem);
 136         SetPageUptodate(page);
 137         kunmap(page);
 138         unlock_page(page);
 139         return 0;
 140
 141 out_unlock_inode:
 142         up_read(&iinfo->i_data_sem);
 143         SetPageError(page);
 144 out_unmap:
 145         kunmap(page);
 146         unlock_page(page);
 147         return err;
 148 }
 149
 150 /*
 151  * symlinks can't do much...
 152  */
 153 const struct address_space_operations udf_symlink_aops = {
 154         .readpage               = udf_symlink_filler,
 155 };