// 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>

   *

   * 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
  ",
  					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]
  ", block, offset);
  
  	dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
  	if (dire == NULL) {
  		ERROR("Failed to allocate squashfs_dir_entry
  ");
  		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]
  ", 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,

  };