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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Squashfs - a compressed read only filesystem for Linux
*
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
* Phillip Lougher <phillip@squashfs.org.uk>
*
* symlink.c
*/
/*
* This file implements code to handle symbolic links.
*
* The data contents of symbolic links are stored inside the symbolic
* link inode within the inode table. This allows the normally small symbolic
* link to be compressed as part of the inode table, achieving much greater
* compression than if the symbolic link was compressed individually.
*/
#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/pagemap.h>
#include <linux/xattr.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
#include "xattr.h"
static int squashfs_symlink_read_folio(struct file *file, struct folio *folio)
{
struct inode *inode = folio->mapping->host;
struct super_block *sb = inode->i_sb;
struct squashfs_sb_info *msblk = sb->s_fs_info;
int index = folio_pos(folio);
u64 block = squashfs_i(inode)->start;
int offset = squashfs_i(inode)->offset;
int length = min_t(int, i_size_read(inode) - index, PAGE_SIZE);
int bytes, copied, error;
void *pageaddr;
struct squashfs_cache_entry *entry;
TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
"%llx, offset %x\n", folio->index, block, offset);
/*
* Skip index bytes into symlink metadata.
*/
if (index) {
bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
index);
if (bytes < 0) {
ERROR("Unable to read symlink [%llx:%x]\n",
squashfs_i(inode)->start,
squashfs_i(inode)->offset);
error = bytes;
goto out;
}
}
/*
* Read length bytes from symlink metadata. Squashfs_read_metadata
* is not used here because it can sleep and we want to use
* kmap_local to map the folio. Instead call the underlying
* squashfs_cache_get routine. As length bytes may overlap metadata
* blocks, we may need to call squashfs_cache_get multiple times.
*/
for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
if (entry->error) {
ERROR("Unable to read symlink [%llx:%x]\n",
squashfs_i(inode)->start,
squashfs_i(inode)->offset);
squashfs_cache_put(entry);
error = entry->error;
goto out;
}
pageaddr = kmap_local_folio(folio, 0);
copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
length - bytes);
if (copied == length - bytes)
memset(pageaddr + length, 0, PAGE_SIZE - length);
else
block = entry->next_index;
kunmap_local(pageaddr);
squashfs_cache_put(entry);
}
flush_dcache_folio(folio);
error = 0;
out:
folio_end_read(folio, error == 0);
return error;
}
const struct address_space_operations squashfs_symlink_aops = {
.read_folio = squashfs_symlink_read_folio
};
const struct inode_operations squashfs_symlink_inode_ops = {
.get_link = page_get_link,
.listxattr = squashfs_listxattr
};
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