decmpfs.h   [plain text]

/*
 * Copyright (c) 2008 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
#ifndef _SYS_DECMPFS_H_
#define _SYS_DECMPFS_H_ 1

#define MAX_DECMPFS_XATTR_SIZE 3802

/*
 NOTE:  decmpfs can only be used by thread-safe filesystems
 */

#define DECMPFS_MAGIC 0x636d7066 /* cmpf */

#define DECMPFS_XATTR_NAME "com.apple.decmpfs" /* extended attribute to use for decmpfs */

typedef struct __attribute__((packed)) {
    /* this structure represents the xattr on disk; the fields below are little-endian */
    uint32_t compression_magic;
    uint32_t compression_type;     /* see the enum below */
    uint64_t uncompressed_size;
    unsigned char attr_bytes[0];   /* the bytes of the attribute after the header */
} decmpfs_disk_header;

typedef struct __attribute__((packed)) {
    /* this structure represents the xattr in memory; the fields below are host-endian */
    uint32_t attr_size;
    uint32_t compression_magic;
    uint32_t compression_type;
    uint64_t uncompressed_size;
    unsigned char attr_bytes[0];   /* the bytes of the attribute after the header */
} decmpfs_header;

/* compression_type values */
enum {
    CMP_Type1       = 1, /* uncompressed data in xattr */
    
    /* additional types defined in AppleFSCompression project */
    
    CMP_MAX         = 255
};

typedef struct {
    void *buf;
    user_ssize_t size;
} decmpfs_vector;

#if KERNEL

#include <kern/locks.h>

#if defined(__i386__) || defined(__x86_64__)
#define DECMPFS_SUPPORTS_SWAP64 1
/* otherwise, no OSCompareAndSwap64, so use a mutex */
#endif

typedef struct decmpfs_cnode {
	uint8_t cmp_state;
	uint8_t cmp_minimal_xattr;       /* if non-zero, this file's com.apple.decmpfs xattr contained only the minimal decmpfs_disk_header */
	uint32_t cmp_type;
	uint32_t lockcount;
	void    *lockowner;              /* cnode's lock owner (if a thread is currently holding an exclusive lock) */
    uint64_t uncompressed_size __attribute__((aligned(8)));
    lck_rw_t compressed_data_lock;
#if !DECMPFS_SUPPORTS_SWAP64
    /* we need a lock since we can't atomically fetch/set 64 bits */
    lck_mtx_t uncompressed_size_mtx;
#endif /* !DECMPFS_SUPPORTS_SWAP64 */
} decmpfs_cnode;

/* return values from decmpfs_file_is_compressed */
enum {
    FILE_TYPE_UNKNOWN      = 0,
    FILE_IS_NOT_COMPRESSED = 1,
    FILE_IS_COMPRESSED     = 2,
    FILE_IS_CONVERTING     = 3  /* file is converting from compressed to decompressed */
};

/* vfs entrypoints */
extern vfs_context_t decmpfs_ctx;

/* client filesystem entrypoints */
void decmpfs_init(void);
void decmpfs_cnode_init(decmpfs_cnode *cp);
void decmpfs_cnode_destroy(decmpfs_cnode *cp);

int decmpfs_hides_rsrc(vfs_context_t ctx, decmpfs_cnode *cp);
int decmpfs_hides_xattr(vfs_context_t ctx, decmpfs_cnode *cp, const char *xattr);

boolean_t decmpfs_trylock_compressed_data(decmpfs_cnode *cp, int exclusive);
void decmpfs_lock_compressed_data(decmpfs_cnode *cp, int exclusive);
void decmpfs_unlock_compressed_data(decmpfs_cnode *cp, int exclusive);

uint32_t decmpfs_cnode_get_vnode_state(decmpfs_cnode *cp);
void decmpfs_cnode_set_vnode_state(decmpfs_cnode *cp, uint32_t state, int skiplock);
uint64_t decmpfs_cnode_get_vnode_cached_size(decmpfs_cnode *cp);

int decmpfs_file_is_compressed(vnode_t vp, decmpfs_cnode *cp);
errno_t decmpfs_validate_compressed_file(vnode_t vp, decmpfs_cnode *cp);
int decmpfs_decompress_file(vnode_t vp, decmpfs_cnode *cp, off_t toSize, int truncate_okay, int skiplock);  /* if toSize == -1, decompress the entire file */
int decmpfs_free_compressed_data(vnode_t vp, decmpfs_cnode *cp);
int decmpfs_update_attributes(vnode_t vp, struct vnode_attr *vap);
/* the following two routines will set *is_compressed to 0 if the file was converted from compressed to decompressed before data could be fetched from the decompressor */
errno_t decmpfs_pagein_compressed(struct vnop_pagein_args *ap, int *is_compressed, decmpfs_cnode *cp);
errno_t decmpfs_read_compressed(struct vnop_read_args *ap, int *is_compressed, decmpfs_cnode *cp);

/* types shared between the kernel and kexts */
typedef int (*decmpfs_validate_compressed_file_func)(vnode_t vp, vfs_context_t ctx, decmpfs_header *hdr);
typedef void (*decmpfs_adjust_fetch_region_func)(vnode_t vp, vfs_context_t ctx, decmpfs_header *hdr, off_t *offset, user_ssize_t *size);
typedef int (*decmpfs_fetch_uncompressed_data_func)(vnode_t vp, vfs_context_t ctx, decmpfs_header *hdr, off_t offset, user_ssize_t size, int nvec, decmpfs_vector *vec, uint64_t *bytes_read);
typedef int (*decmpfs_free_compressed_data_func)(vnode_t vp, vfs_context_t ctx, decmpfs_header *hdr);

#define DECMPFS_REGISTRATION_VERSION 1
typedef struct {
    int                                   decmpfs_registration;
    decmpfs_validate_compressed_file_func validate;
    decmpfs_adjust_fetch_region_func      adjust_fetch;
    decmpfs_fetch_uncompressed_data_func  fetch;
    decmpfs_free_compressed_data_func     free_data;
} decmpfs_registration;

/* hooks for kexts to call */
errno_t register_decmpfs_decompressor(uint32_t compression_type, decmpfs_registration *registration);
errno_t unregister_decmpfs_decompressor(uint32_t compression_type, decmpfs_registration *registration);

#endif /* KERNEL */

#endif /* _SYS_DECMPFS_H_ */