/*
* Squashfs - a compressed read only filesystem for Linux
*
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
* Phillip Lougher <phillip@squashfs.org.uk>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2,
* or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* dir.c
*/
/*
* This file implements code to read directories from disk.
*
* See namei.c for a description of directory organisation on disk.
*/
#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
static const unsigned char squashfs_filetype_table[] = {
DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK
};
/*
* Lookup offset (f_pos) in the directory index, returning the
* metadata block containing it.
*
* If we get an error reading the index then return the part of the index
* (if any) we have managed to read - the index isn't essential, just
* quicker.
*/
static int get_dir_index_using_offset(struct super_block *sb,
u64 *next_block, int *next_offset, u64 index_start, int index_offset,
int i_count, u64 f_pos)
{
struct squashfs_sb_info *msblk = sb->s_fs_info;
int err, i, index, length = 0;
unsigned int size;
struct squashfs_dir_index dir_index;
TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n",
i_count, f_pos);
/*
* Translate from external f_pos to the internal f_pos. This
* is offset by 3 because we invent "." and ".." entries which are
* not actually stored in the directory.
*/
if (f_pos <= 3)
return f_pos;
f_pos -= 3;
for (i = 0; i < i_count; i++) {
err = squashfs_read_metadata(sb, &dir_index, &index_start,
&index_offset, sizeof(dir_index));
if (err < 0)
break;
index = le32_to_cpu(dir_index.index);
if (index > f_pos)
/*
* Found the index we're looking for.
*/
break;
size = le32_to_cpu(dir_index.size) + 1;
/* size should never be larger than SQUASHFS_NAME_LEN */
if (size > SQUASHFS_NAME_LEN)
break;
err = squashfs_read_metadata(sb, NULL, &index_start,
&index_offset, size);
if (err < 0)
break;
length = index;
*next_block = le32_to_cpu(dir_index.start_block) +
msblk->directory_table;
}
*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
/*
* Translate back from internal f_pos to external f_pos.
*/
return length + 3;
}
static int squashfs_readdir(struct file *file, struct dir_context *ctx)
{
struct inode *inode = file_inode(file);
struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
u64 block = squashfs_i(inode)->start + msblk->directory_table;
int offset = squashfs_i(inode)->offset, length, err;
unsigned int inode_number, dir_count, size, type;
struct squashfs_dir_header dirh;
struct squashfs_dir_entry *dire;
TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset);
dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
if (dire == NULL) {
ERROR("Failed to allocate squashfs_dir_entry\n");
goto finish;
}
/*
* Return "." and ".." entries as the first two filenames in the
* directory. To maximise compression these two entries are not
* stored in the directory, and so we invent them here.
*
* It also means that the external f_pos is offset by 3 from the
* on-disk directory f_pos.
*/
while (ctx->pos < 3) {
char *name;
int i_ino;
if (ctx->pos == 0) {
name = ".";
size = 1;
i_ino = inode->i_ino;
} else {
name = "..";
size = 2;
i_ino = squashfs_i(inode)->parent;
}
if (!dir_emit(ctx, name, size, i_ino,
squashfs_filetype_table[1]))
goto finish;
ctx->pos += size;
}
length = get_dir_index_using_offset(inode->i_sb, &block, &offset,
squashfs_i(inode)->dir_idx_start,
squashfs_i(inode)->dir_idx_offset,
squashfs_i(inode)->dir_idx_cnt,
ctx->pos);
while (length < i_size_read(inode)) {
/*
* Read directory header
*/
err = squashfs_read_metadata(inode->i_sb, &dirh, &block,
&offset, sizeof(dirh));
if (err < 0)
goto failed_read;
length += sizeof(dirh);
dir_count = le32_to_cpu(dirh.count) + 1;
if (dir_count > SQUASHFS_DIR_COUNT)
goto failed_read;
while (dir_count--) {
/*
* Read directory entry.
*/
err = squashfs_read_metadata(inode->i_sb, dire, &block,
&offset, sizeof(*dire));
if (err < 0)
goto failed_read;
size = le16_to_cpu(dire->size) + 1;
/* size should never be larger than SQUASHFS_NAME_LEN */
if (size > SQUASHFS_NAME_LEN)
goto failed_read;
err = squashfs_read_metadata(inode->i_sb, dire->name,
&block, &offset, size);
if (err < 0)
goto failed_read;
length += sizeof(*dire) + size;
if (ctx->pos >= length)
continue;
dire->name[size] = '\0';
inode_number = le32_to_cpu(dirh.inode_number) +
((short) le16_to_cpu(dire->inode_number));
type = le16_to_cpu(dire->type);
if (type > SQUASHFS_MAX_DIR_TYPE)
goto failed_read;
if (!dir_emit(ctx, dire->name, size,
inode_number,
squashfs_filetype_table[type]))
goto finish;
ctx->pos = length;
}
}
finish:
kfree(dire);
return 0;
failed_read:
ERROR("Unable to read directory block [%llx:%x]\n", block, offset);
kfree(dire);
return 0;
}
const struct file_operations squashfs_dir_ops = {
.read = generic_read_dir,
.iterate_shared = squashfs_readdir,
.llseek = generic_file_llseek,
};
