1 /* SPDX-License-Identifier: GPL-2.0-only OR Apache-2.0 */
2 /*
3  * EROFS (Enhanced ROM File System) on-disk format definition
4  *
5  * Copyright (C) 2017-2018 HUAWEI, Inc.
6  *             https://www.huawei.com/
7  * Copyright (C) 2021, Alibaba Cloud
8  */
9 #ifndef __EROFS_FS_H
10 #define __EROFS_FS_H
11 
12 #define EROFS_SUPER_OFFSET      1024
13 
14 #define EROFS_FEATURE_COMPAT_SB_CHKSUM          0x00000001
15 #define EROFS_FEATURE_COMPAT_MTIME              0x00000002
16 
17 /*
18  * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
19  * be incompatible with this kernel version.
20  */
21 #define EROFS_FEATURE_INCOMPAT_ZERO_PADDING	0x00000001
22 #define EROFS_FEATURE_INCOMPAT_COMPR_CFGS	0x00000002
23 #define EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER	0x00000002
24 #define EROFS_FEATURE_INCOMPAT_CHUNKED_FILE	0x00000004
25 #define EROFS_FEATURE_INCOMPAT_DEVICE_TABLE	0x00000008
26 #define EROFS_FEATURE_INCOMPAT_COMPR_HEAD2	0x00000008
27 #define EROFS_FEATURE_INCOMPAT_ZTAILPACKING	0x00000010
28 #define EROFS_ALL_FEATURE_INCOMPAT		\
29 	(EROFS_FEATURE_INCOMPAT_ZERO_PADDING | \
30 	 EROFS_FEATURE_INCOMPAT_COMPR_CFGS | \
31 	 EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER | \
32 	 EROFS_FEATURE_INCOMPAT_CHUNKED_FILE | \
33 	 EROFS_FEATURE_INCOMPAT_DEVICE_TABLE | \
34 	 EROFS_FEATURE_INCOMPAT_COMPR_HEAD2 | \
35 	 EROFS_FEATURE_INCOMPAT_ZTAILPACKING)
36 
37 #define EROFS_SB_EXTSLOT_SIZE	16
38 
39 struct erofs_deviceslot {
40 	u8 tag[64];		/* digest(sha256), etc. */
41 	__le32 blocks;		/* total fs blocks of this device */
42 	__le32 mapped_blkaddr;	/* map starting at mapped_blkaddr */
43 	u8 reserved[56];
44 };
45 #define EROFS_DEVT_SLOT_SIZE	sizeof(struct erofs_deviceslot)
46 
47 /* erofs on-disk super block (currently 128 bytes) */
48 struct erofs_super_block {
49 	__le32 magic;           /* file system magic number */
50 	__le32 checksum;        /* crc32c(super_block) */
51 	__le32 feature_compat;
52 	__u8 blkszbits;         /* support block_size == PAGE_SIZE only */
53 	__u8 sb_extslots;	/* superblock size = 128 + sb_extslots * 16 */
54 
55 	__le16 root_nid;	/* nid of root directory */
56 	__le64 inos;            /* total valid ino # (== f_files - f_favail) */
57 
58 	__le64 build_time;      /* compact inode time derivation */
59 	__le32 build_time_nsec;	/* compact inode time derivation in ns scale */
60 	__le32 blocks;          /* used for statfs */
61 	__le32 meta_blkaddr;	/* start block address of metadata area */
62 	__le32 xattr_blkaddr;	/* start block address of shared xattr area */
63 	__u8 uuid[16];          /* 128-bit uuid for volume */
64 	__u8 volume_name[16];   /* volume name */
65 	__le32 feature_incompat;
66 	union {
67 		/* bitmap for available compression algorithms */
68 		__le16 available_compr_algs;
69 		/* customized sliding window size instead of 64k by default */
70 		__le16 lz4_max_distance;
71 	} __packed u1;
72 	__le16 extra_devices;	/* # of devices besides the primary device */
73 	__le16 devt_slotoff;	/* startoff = devt_slotoff * devt_slotsize */
74 	__u8 reserved2[38];
75 };
76 
77 /*
78  * erofs inode datalayout (i_format in on-disk inode):
79  * 0 - uncompressed flat inode without tail-packing inline data:
80  * inode, [xattrs], ... | ... | no-holed data
81  * 1 - compressed inode with non-compact indexes:
82  * inode, [xattrs], [map_header], extents ... | ...
83  * 2 - uncompressed flat inode with tail-packing inline data:
84  * inode, [xattrs], tailpacking data, ... | ... | no-holed data
85  * 3 - compressed inode with compact indexes:
86  * inode, [xattrs], map_header, extents ... | ...
87  * 4 - chunk-based inode with (optional) multi-device support:
88  * inode, [xattrs], chunk indexes ... | ...
89  * 5~7 - reserved
90  */
91 enum {
92 	EROFS_INODE_FLAT_PLAIN			= 0,
93 	EROFS_INODE_FLAT_COMPRESSION_LEGACY	= 1,
94 	EROFS_INODE_FLAT_INLINE			= 2,
95 	EROFS_INODE_FLAT_COMPRESSION		= 3,
96 	EROFS_INODE_CHUNK_BASED			= 4,
97 	EROFS_INODE_DATALAYOUT_MAX
98 };
99 
erofs_inode_is_data_compressed(unsigned int datamode)100 static inline bool erofs_inode_is_data_compressed(unsigned int datamode)
101 {
102 	return datamode == EROFS_INODE_FLAT_COMPRESSION ||
103 		datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
104 }
105 
106 /* bit definitions of inode i_format */
107 #define EROFS_I_VERSION_BITS            1
108 #define EROFS_I_DATALAYOUT_BITS         3
109 
110 #define EROFS_I_VERSION_BIT             0
111 #define EROFS_I_DATALAYOUT_BIT          1
112 
113 #define EROFS_I_ALL	\
114 	((1 << (EROFS_I_DATALAYOUT_BIT + EROFS_I_DATALAYOUT_BITS)) - 1)
115 
116 /* indicate chunk blkbits, thus 'chunksize = blocksize << chunk blkbits' */
117 #define EROFS_CHUNK_FORMAT_BLKBITS_MASK		0x001F
118 /* with chunk indexes or just a 4-byte blkaddr array */
119 #define EROFS_CHUNK_FORMAT_INDEXES		0x0020
120 
121 #define EROFS_CHUNK_FORMAT_ALL	\
122 	(EROFS_CHUNK_FORMAT_BLKBITS_MASK | EROFS_CHUNK_FORMAT_INDEXES)
123 
124 struct erofs_inode_chunk_info {
125 	__le16 format;		/* chunk blkbits, etc. */
126 	__le16 reserved;
127 };
128 
129 /* 32-byte reduced form of an ondisk inode */
130 struct erofs_inode_compact {
131 	__le16 i_format;	/* inode format hints */
132 
133 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
134 	__le16 i_xattr_icount;
135 	__le16 i_mode;
136 	__le16 i_nlink;
137 	__le32 i_size;
138 	__le32 i_reserved;
139 	union {
140 		/* total compressed blocks for compressed inodes */
141 		__le32 compressed_blocks;
142 		/* block address for uncompressed flat inodes */
143 		__le32 raw_blkaddr;
144 
145 		/* for device files, used to indicate old/new device # */
146 		__le32 rdev;
147 
148 		/* for chunk-based files, it contains the summary info */
149 		struct erofs_inode_chunk_info c;
150 	} i_u;
151 	__le32 i_ino;           /* only used for 32-bit stat compatibility */
152 	__le16 i_uid;
153 	__le16 i_gid;
154 	__le32 i_reserved2;
155 };
156 
157 /* 32-byte on-disk inode */
158 #define EROFS_INODE_LAYOUT_COMPACT	0
159 /* 64-byte on-disk inode */
160 #define EROFS_INODE_LAYOUT_EXTENDED	1
161 
162 /* 64-byte complete form of an ondisk inode */
163 struct erofs_inode_extended {
164 	__le16 i_format;	/* inode format hints */
165 
166 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
167 	__le16 i_xattr_icount;
168 	__le16 i_mode;
169 	__le16 i_reserved;
170 	__le64 i_size;
171 	union {
172 		/* total compressed blocks for compressed inodes */
173 		__le32 compressed_blocks;
174 		/* block address for uncompressed flat inodes */
175 		__le32 raw_blkaddr;
176 
177 		/* for device files, used to indicate old/new device # */
178 		__le32 rdev;
179 
180 		/* for chunk-based files, it contains the summary info */
181 		struct erofs_inode_chunk_info c;
182 	} i_u;
183 
184 	/* only used for 32-bit stat compatibility */
185 	__le32 i_ino;
186 
187 	__le32 i_uid;
188 	__le32 i_gid;
189 	__le64 i_mtime;
190 	__le32 i_mtime_nsec;
191 	__le32 i_nlink;
192 	__u8   i_reserved2[16];
193 };
194 
195 #define EROFS_MAX_SHARED_XATTRS         (128)
196 /* h_shared_count between 129 ... 255 are special # */
197 #define EROFS_SHARED_XATTR_EXTENT       (255)
198 
199 /*
200  * inline xattrs (n == i_xattr_icount):
201  * erofs_xattr_ibody_header(1) + (n - 1) * 4 bytes
202  *          12 bytes           /                   \
203  *                            /                     \
204  *                           /-----------------------\
205  *                           |  erofs_xattr_entries+ |
206  *                           +-----------------------+
207  * inline xattrs must starts in erofs_xattr_ibody_header,
208  * for read-only fs, no need to introduce h_refcount
209  */
210 struct erofs_xattr_ibody_header {
211 	__le32 h_reserved;
212 	__u8   h_shared_count;
213 	__u8   h_reserved2[7];
214 	__le32 h_shared_xattrs[];       /* shared xattr id array */
215 };
216 
217 /* Name indexes */
218 #define EROFS_XATTR_INDEX_USER              1
219 #define EROFS_XATTR_INDEX_POSIX_ACL_ACCESS  2
220 #define EROFS_XATTR_INDEX_POSIX_ACL_DEFAULT 3
221 #define EROFS_XATTR_INDEX_TRUSTED           4
222 #define EROFS_XATTR_INDEX_LUSTRE            5
223 #define EROFS_XATTR_INDEX_SECURITY          6
224 
225 /* xattr entry (for both inline & shared xattrs) */
226 struct erofs_xattr_entry {
227 	__u8   e_name_len;      /* length of name */
228 	__u8   e_name_index;    /* attribute name index */
229 	__le16 e_value_size;    /* size of attribute value */
230 	/* followed by e_name and e_value */
231 	char   e_name[];        /* attribute name */
232 };
233 
erofs_xattr_ibody_size(__le16 i_xattr_icount)234 static inline unsigned int erofs_xattr_ibody_size(__le16 i_xattr_icount)
235 {
236 	if (!i_xattr_icount)
237 		return 0;
238 
239 	return sizeof(struct erofs_xattr_ibody_header) +
240 		sizeof(__u32) * (le16_to_cpu(i_xattr_icount) - 1);
241 }
242 
243 #define EROFS_XATTR_ALIGN(size) round_up(size, sizeof(struct erofs_xattr_entry))
244 
erofs_xattr_entry_size(struct erofs_xattr_entry * e)245 static inline unsigned int erofs_xattr_entry_size(struct erofs_xattr_entry *e)
246 {
247 	return EROFS_XATTR_ALIGN(sizeof(struct erofs_xattr_entry) +
248 				 e->e_name_len + le16_to_cpu(e->e_value_size));
249 }
250 
251 /* represent a zeroed chunk (hole) */
252 #define EROFS_NULL_ADDR			-1
253 
254 /* 4-byte block address array */
255 #define EROFS_BLOCK_MAP_ENTRY_SIZE	sizeof(__le32)
256 
257 /* 8-byte inode chunk indexes */
258 struct erofs_inode_chunk_index {
259 	__le16 advise;		/* always 0, don't care for now */
260 	__le16 device_id;	/* back-end storage id (with bits masked) */
261 	__le32 blkaddr;		/* start block address of this inode chunk */
262 };
263 
264 /* maximum supported size of a physical compression cluster */
265 #define Z_EROFS_PCLUSTER_MAX_SIZE	(1024 * 1024)
266 
267 /* available compression algorithm types (for h_algorithmtype) */
268 enum {
269 	Z_EROFS_COMPRESSION_LZ4		= 0,
270 	Z_EROFS_COMPRESSION_LZMA	= 1,
271 	Z_EROFS_COMPRESSION_MAX
272 };
273 #define Z_EROFS_ALL_COMPR_ALGS		((1 << Z_EROFS_COMPRESSION_MAX) - 1)
274 
275 /* 14 bytes (+ length field = 16 bytes) */
276 struct z_erofs_lz4_cfgs {
277 	__le16 max_distance;
278 	__le16 max_pclusterblks;
279 	u8 reserved[10];
280 } __packed;
281 
282 /* 14 bytes (+ length field = 16 bytes) */
283 struct z_erofs_lzma_cfgs {
284 	__le32 dict_size;
285 	__le16 format;
286 	u8 reserved[8];
287 } __packed;
288 
289 #define Z_EROFS_LZMA_MAX_DICT_SIZE	(8 * Z_EROFS_PCLUSTER_MAX_SIZE)
290 
291 /*
292  * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
293  *  e.g. for 4k logical cluster size,      4B        if compacted 2B is off;
294  *                                  (4B) + 2B + (4B) if compacted 2B is on.
295  * bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
296  * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
297  * bit 3 : tailpacking inline pcluster (0 - off; 1 - on)
298  */
299 #define Z_EROFS_ADVISE_COMPACTED_2B		0x0001
300 #define Z_EROFS_ADVISE_BIG_PCLUSTER_1		0x0002
301 #define Z_EROFS_ADVISE_BIG_PCLUSTER_2		0x0004
302 #define Z_EROFS_ADVISE_INLINE_PCLUSTER		0x0008
303 
304 struct z_erofs_map_header {
305 	__le16	h_reserved1;
306 	/* indicates the encoded size of tailpacking data */
307 	__le16  h_idata_size;
308 	__le16	h_advise;
309 	/*
310 	 * bit 0-3 : algorithm type of head 1 (logical cluster type 01);
311 	 * bit 4-7 : algorithm type of head 2 (logical cluster type 11).
312 	 */
313 	__u8	h_algorithmtype;
314 	/*
315 	 * bit 0-2 : logical cluster bits - 12, e.g. 0 for 4096;
316 	 * bit 3-7 : reserved.
317 	 */
318 	__u8	h_clusterbits;
319 };
320 
321 #define Z_EROFS_VLE_LEGACY_HEADER_PADDING       8
322 
323 /*
324  * Fixed-sized output compression on-disk logical cluster type:
325  *    0   - literal (uncompressed) lcluster
326  *    1,3 - compressed lcluster (for HEAD lclusters)
327  *    2   - compressed lcluster (for NONHEAD lclusters)
328  *
329  * In detail,
330  *    0 - literal (uncompressed) lcluster,
331  *        di_advise = 0
332  *        di_clusterofs = the literal data offset of the lcluster
333  *        di_blkaddr = the blkaddr of the literal pcluster
334  *
335  *    1,3 - compressed lcluster (for HEAD lclusters)
336  *        di_advise = 1 or 3
337  *        di_clusterofs = the decompressed data offset of the lcluster
338  *        di_blkaddr = the blkaddr of the compressed pcluster
339  *
340  *    2 - compressed lcluster (for NONHEAD lclusters)
341  *        di_advise = 2
342  *        di_clusterofs =
343  *           the decompressed data offset in its own HEAD lcluster
344  *        di_u.delta[0] = distance to this HEAD lcluster
345  *        di_u.delta[1] = distance to the next HEAD lcluster
346  */
347 enum {
348 	Z_EROFS_VLE_CLUSTER_TYPE_PLAIN		= 0,
349 	Z_EROFS_VLE_CLUSTER_TYPE_HEAD1		= 1,
350 	Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD	= 2,
351 	Z_EROFS_VLE_CLUSTER_TYPE_HEAD2		= 3,
352 	Z_EROFS_VLE_CLUSTER_TYPE_MAX
353 };
354 
355 #define Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS        2
356 #define Z_EROFS_VLE_DI_CLUSTER_TYPE_BIT         0
357 
358 /*
359  * D0_CBLKCNT will be marked _only_ at the 1st non-head lcluster to store the
360  * compressed block count of a compressed extent (in logical clusters, aka.
361  * block count of a pcluster).
362  */
363 #define Z_EROFS_VLE_DI_D0_CBLKCNT		(1 << 11)
364 
365 struct z_erofs_vle_decompressed_index {
366 	__le16 di_advise;
367 	/* where to decompress in the head lcluster */
368 	__le16 di_clusterofs;
369 
370 	union {
371 		/* for the HEAD lclusters */
372 		__le32 blkaddr;
373 		/*
374 		 * for the NONHEAD lclusters
375 		 * [0] - distance to its HEAD lcluster
376 		 * [1] - distance to the next HEAD lcluster
377 		 */
378 		__le16 delta[2];
379 	} di_u;
380 };
381 
382 #define Z_EROFS_VLE_LEGACY_INDEX_ALIGN(size) \
383 	(round_up(size, sizeof(struct z_erofs_vle_decompressed_index)) + \
384 	 sizeof(struct z_erofs_map_header) + Z_EROFS_VLE_LEGACY_HEADER_PADDING)
385 
386 /* dirent sorts in alphabet order, thus we can do binary search */
387 struct erofs_dirent {
388 	__le64 nid;     /* node number */
389 	__le16 nameoff; /* start offset of file name */
390 	__u8 file_type; /* file type */
391 	__u8 reserved;  /* reserved */
392 } __packed;
393 
394 /*
395  * EROFS file types should match generic FT_* types and
396  * it seems no need to add BUILD_BUG_ONs since potential
397  * unmatchness will break other fses as well...
398  */
399 
400 #define EROFS_NAME_LEN      255
401 
402 /* check the EROFS on-disk layout strictly at compile time */
erofs_check_ondisk_layout_definitions(void)403 static inline void erofs_check_ondisk_layout_definitions(void)
404 {
405 	BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
406 	BUILD_BUG_ON(sizeof(struct erofs_inode_compact) != 32);
407 	BUILD_BUG_ON(sizeof(struct erofs_inode_extended) != 64);
408 	BUILD_BUG_ON(sizeof(struct erofs_xattr_ibody_header) != 12);
409 	BUILD_BUG_ON(sizeof(struct erofs_xattr_entry) != 4);
410 	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_info) != 4);
411 	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) != 8);
412 	BUILD_BUG_ON(sizeof(struct z_erofs_map_header) != 8);
413 	BUILD_BUG_ON(sizeof(struct z_erofs_vle_decompressed_index) != 8);
414 	BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);
415 	/* keep in sync between 2 index structures for better extendibility */
416 	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) !=
417 		     sizeof(struct z_erofs_vle_decompressed_index));
418 	BUILD_BUG_ON(sizeof(struct erofs_deviceslot) != 128);
419 
420 	BUILD_BUG_ON(BIT(Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) <
421 		     Z_EROFS_VLE_CLUSTER_TYPE_MAX - 1);
422 }
423 
424 #endif
425