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/*
* Unsquash a squashfs filesystem. This is a highly compressed read only
* filesystem.
*
* Copyright (c) 2019, 2022, 2023
* 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* unsquash-34.c
*
* Helper functions used by unsquash-3 and unsquash-4.
*/
#include "unsquashfs.h"
static unsigned int **inumber_table = NULL;
static char ***lookup_table = NULL;
long long *alloc_index_table(int indexes)
{
static long long *alloc_table = NULL;
static int alloc_size = 0;
int length = indexes * sizeof(long long);
if(alloc_size < length || length == 0) {
long long *table = realloc(alloc_table, length);
if(table == NULL && length !=0)
MEM_ERROR();
alloc_table = table;
alloc_size = length;
}
return alloc_table;
}
/* These functions implement a bit-table to track whether directories have been
* already visited. This is to trap corrupted filesystems which have multiple
* links to the same directory, which is invalid, and which may also create
* a directory loop, where Unsquashfs will endlessly recurse until either
* the pathname is too large (extracting), or the stack overflows.
*
* Each index entry is 8 Kbytes, and tracks 65536 inode numbers. The index is
* allocated on demand because Unsquashfs may not walk the complete filesystem.
*/
static void create_inumber_table()
{
int indexes = INUMBER_INDEXES(sBlk.s.inodes);
inumber_table = malloc(indexes * sizeof(unsigned int *));
if(inumber_table == NULL)
MEM_ERROR();
memset(inumber_table, 0, indexes * sizeof(unsigned int *));
}
int inumber_lookup(unsigned int number)
{
int index = INUMBER_INDEX(number - 1);
int offset = INUMBER_OFFSET(number - 1);
int bit = INUMBER_BIT(number - 1);
if(inumber_table == NULL)
create_inumber_table();
/* Lookup number in the bit table */
if(inumber_table[index] && (inumber_table[index][offset] & bit))
return TRUE;
if(inumber_table[index] == NULL) {
inumber_table[index] = malloc(INUMBER_BYTES);
if(inumber_table[index] == NULL)
MEM_ERROR();
memset(inumber_table[index], 0, INUMBER_BYTES);
}
inumber_table[index][offset] |= bit;
return FALSE;
}
void free_inumber_table()
{
int i, indexes = INUMBER_INDEXES(sBlk.s.inodes);
if(inumber_table) {
for(i = 0; i < indexes; i++)
if(inumber_table[i])
free(inumber_table[i]);
free(inumber_table);
inumber_table = NULL;
}
}
/* These functions implement a lookup table to track creation of (non-directory)
* inodes, and to discover if a hard-link to a previously created file should
* be made.
*
* Each index entry is 32 Kbytes, and tracks 4096 inode numbers. The index is
* allocated on demand because Unsquashfs may not walk the complete filesystem.
*/
static void create_lookup_table()
{
int indexes = LOOKUP_INDEXES(sBlk.s.inodes);
lookup_table = malloc(indexes * sizeof(char *));
if(lookup_table == NULL)
MEM_ERROR();
memset(lookup_table, 0, indexes * sizeof(char *));
}
char *lookup(unsigned int number)
{
int index = LOOKUP_INDEX(number - 1);
int offset = LOOKUP_OFFSET(number - 1);
if(lookup_table == NULL)
create_lookup_table();
/* Lookup number in table */
if(lookup_table[index] == NULL)
return NULL;
return lookup_table[index][offset];
}
void insert_lookup(unsigned int number, char *pathname)
{
int index = LOOKUP_INDEX(number - 1);
int offset = LOOKUP_OFFSET(number - 1);
if(lookup_table == NULL)
create_lookup_table();
if(lookup_table[index] == NULL) {
lookup_table[index] = malloc(LOOKUP_BYTES);
if(lookup_table[index] == NULL)
MEM_ERROR();
memset(lookup_table[index], 0, LOOKUP_BYTES);
}
lookup_table[index][offset] = pathname;
}
void free_lookup_table(int free_pathname)
{
int i, indexes = LOOKUP_INDEXES(sBlk.s.inodes);
if(lookup_table) {
for(i = 0; i < indexes; i++)
if(lookup_table[i]) {
if(free_pathname) {
int j;
for(j = 0; j < LOOKUP_OFFSETS; j++)
if(lookup_table[i][j])
free(lookup_table[i][j]);
}
free(lookup_table[i]);
}
free(lookup_table);
lookup_table = NULL;
}
}
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