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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Squashfs - a compressed read only filesystem for Linux4 *5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 20086 * Phillip Lougher <phillip@squashfs.org.uk>7 *8 * symlink.c9 */10 11/*12 * This file implements code to handle symbolic links.13 *14 * The data contents of symbolic links are stored inside the symbolic15 * link inode within the inode table. This allows the normally small symbolic16 * link to be compressed as part of the inode table, achieving much greater17 * compression than if the symbolic link was compressed individually.18 */19 20#include <linux/fs.h>21#include <linux/vfs.h>22#include <linux/kernel.h>23#include <linux/string.h>24#include <linux/pagemap.h>25#include <linux/xattr.h>26 27#include "squashfs_fs.h"28#include "squashfs_fs_sb.h"29#include "squashfs_fs_i.h"30#include "squashfs.h"31#include "xattr.h"32 33static int squashfs_symlink_read_folio(struct file *file, struct folio *folio)34{35 struct inode *inode = folio->mapping->host;36 struct super_block *sb = inode->i_sb;37 struct squashfs_sb_info *msblk = sb->s_fs_info;38 int index = folio_pos(folio);39 u64 block = squashfs_i(inode)->start;40 int offset = squashfs_i(inode)->offset;41 int length = min_t(int, i_size_read(inode) - index, PAGE_SIZE);42 int bytes, copied, error;43 void *pageaddr;44 struct squashfs_cache_entry *entry;45 46 TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "47 "%llx, offset %x\n", folio->index, block, offset);48 49 /*50 * Skip index bytes into symlink metadata.51 */52 if (index) {53 bytes = squashfs_read_metadata(sb, NULL, &block, &offset,54 index);55 if (bytes < 0) {56 ERROR("Unable to read symlink [%llx:%x]\n",57 squashfs_i(inode)->start,58 squashfs_i(inode)->offset);59 error = bytes;60 goto out;61 }62 }63 64 /*65 * Read length bytes from symlink metadata. Squashfs_read_metadata66 * is not used here because it can sleep and we want to use67 * kmap_local to map the folio. Instead call the underlying68 * squashfs_cache_get routine. As length bytes may overlap metadata69 * blocks, we may need to call squashfs_cache_get multiple times.70 */71 for (bytes = 0; bytes < length; offset = 0, bytes += copied) {72 entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);73 if (entry->error) {74 ERROR("Unable to read symlink [%llx:%x]\n",75 squashfs_i(inode)->start,76 squashfs_i(inode)->offset);77 squashfs_cache_put(entry);78 error = entry->error;79 goto out;80 }81 82 pageaddr = kmap_local_folio(folio, 0);83 copied = squashfs_copy_data(pageaddr + bytes, entry, offset,84 length - bytes);85 if (copied == length - bytes)86 memset(pageaddr + length, 0, PAGE_SIZE - length);87 else88 block = entry->next_index;89 kunmap_local(pageaddr);90 squashfs_cache_put(entry);91 }92 93 flush_dcache_folio(folio);94 error = 0;95out:96 folio_end_read(folio, error == 0);97 return error;98}99 100 101const struct address_space_operations squashfs_symlink_aops = {102 .read_folio = squashfs_symlink_read_folio103};104 105const struct inode_operations squashfs_symlink_inode_ops = {106 .get_link = page_get_link,107 .listxattr = squashfs_listxattr108};109 110