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     €ДГѓ}°‹АВБ %(    /* SPDX-License-Identifier: GPL-2.0 */
/*
 * fs-verity: read-only file-based authenticity protection
 *
 * This header declares the interface between the fs/verity/ support layer and
 * filesystems that support fs-verity.
 *
 * Copyright 2019 Google LLC
 */

#ifndef _LINUX_FSVERITY_H
#define _LINUX_FSVERITY_H

#include <linux/fs.h>
#include <linux/mm.h>
#include <crypto/hash_info.h>
#include <crypto/sha2.h>
#include <uapi/linux/fsverity.h>

/*
 * Largest digest size among all hash algorithms supported by fs-verity.
 * Currently assumed to be <= size of fsverity_descriptor::root_hash.
 */
#define FS_VERITY_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE

/* Arbitrary limit to bound the kmalloc() size.  Can be changed. */
#define FS_VERITY_MAX_DESCRIPTOR_SIZE	16384

/* Verity operations for filesystems */
struct fsverity_operations {

	/**
	 * Begin enabling verity on the given file.
	 *
	 * @filp: a readonly file descriptor for the file
	 *
	 * The filesystem must do any needed filesystem-specific preparations
	 * for enabling verity, e.g. evicting inline data.  It also must return
	 * -EBUSY if verity is already being enabled on the given file.
	 *
	 * i_rwsem is held for write.
	 *
	 * Return: 0 on success, -errno on failure
	 */
	int (*begin_enable_verity)(struct file *filp);

	/**
	 * End enabling verity on the given file.
	 *
	 * @filp: a readonly file descriptor for the file
	 * @desc: the verity descriptor to write, or NULL on failure
	 * @desc_size: size of verity descriptor, or 0 on failure
	 * @merkle_tree_size: total bytes the Merkle tree took up
	 *
	 * If desc == NULL, then enabling verity failed and the filesystem only
	 * must do any necessary cleanups.  Else, it must also store the given
	 * verity descriptor to a fs-specific location associated with the inode
	 * and do any fs-specific actions needed to mark the inode as a verity
	 * inode, e.g. setting a bit in the on-disk inode.  The filesystem is
	 * also responsible for setting the S_VERITY flag in the VFS inode.
	 *
	 * i_rwsem is held for write, but it may have been dropped between
	 * ->begin_enable_verity() and ->end_enable_verity().
	 *
	 * Return: 0 on success, -errno on failure
	 */
	int (*end_enable_verity)(struct file *filp, const void *desc,
				 size_t desc_size, u64 merkle_tree_size);

	/**
	 * Get the verity descriptor of the given inode.
	 *
	 * @inode: an inode with the S_VERITY flag set
	 * @buf: buffer in which to place the verity descriptor
	 * @bufsize: size of @buf, or 0 to retrieve the size only
	 *
	 * If bufsize == 0, then the size of the verity descriptor is returned.
	 * Otherwise the verity descriptor is written to 'buf' and its actual
	 * size is returned; -ERANGE is returned if it's too large.  This may be
	 * called by multiple processes concurrently on the same inode.
	 *
	 * Return: the size on success, -errno on failure
	 */
	int (*get_verity_descriptor)(struct inode *inode, void *buf,
				     size_t bufsize);

	/**
	 * Read a Merkle tree page of the given inode.
	 *
	 * @inode: the inode
	 * @index: 0-based index of the page within the Merkle tree
	 * @num_ra_pages: The number of Merkle tree pages that should be
	 *		  prefetched starting at @index if the page at @index
	 *		  isn't already cached.  Implementations may ignore this
	 *		  argument; it's only a performance optimization.
	 *
	 * This can be called at any time on an open verity file.  It may be
	 * called by multiple processes concurrently, even with the same page.
	 *
	 * Note that this must retrieve a *page*, not necessarily a *block*.
	 *
	 * Return: the page on success, ERR_PTR() on failure
	 */
	struct page *(*read_merkle_tree_page)(struct inode *inode,
					      pgoff_t index,
					      unsigned long num_ra_pages);

	/**
	 * Write a Merkle tree block to the given inode.
	 *
	 * @inode: the inode for which the Merkle tree is being built
	 * @buf: the Merkle tree block to write
	 * @pos: the position of the block in the Merkle tree (in bytes)
	 * @size: the Merkle tree block size (in bytes)
	 *
	 * This is only called between ->be