root/fs/hpfs/hpfs.h

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INCLUDED FROM


DEFINITIONS

This source file includes following definitions.
  1. de_down_pointer
  2. dnode_first_de
  3. dnode_end_de
  4. de_next_de
  5. ea_name
  6. ea_value
  7. ea_next_ea
  8. ea_indirect_length
  9. ea_indirect_secno

   1 /* The paper
   2 
   3      Duncan, Roy
   4      Design goals and implementation of the new High Performance File System
   5      Microsoft Systems Journal  Sept 1989  v4 n5 p1(13)
   6 
   7    describes what HPFS looked like when it was new, and it is the source
   8    of most of the information given here.  The rest is conjecture.
   9 
  10    For definitive information on the Duncan paper, see it, not this file.
  11    For definitive information on HPFS, ask somebody else -- this is guesswork.
  12    There are certain to be many mistakes. */
  13 
  14 /* Notation */
  15 
  16 typedef unsigned secno;                 /* sector number, partition relative */
  17 
  18 typedef secno dnode_secno;              /* sector number of a dnode */
  19 typedef secno fnode_secno;              /* sector number of an fnode */
  20 typedef secno anode_secno;              /* sector number of an anode */
  21 
  22 /* sector 0 */
  23 
  24 /* The boot block is very like a FAT boot block, except that the
  25    29h signature byte is 28h instead, and the ID string is "HPFS". */
  26 
  27 struct hpfs_boot_block
  28 {
  29   unsigned char jmp[3];
  30   unsigned char oem_id[8];
  31   unsigned char bytes_per_sector[2];    /* 512 */
  32   unsigned char sectors_per_cluster;
  33   unsigned char n_reserved_sectors[2];
  34   unsigned char n_fats;
  35   unsigned char n_rootdir_entries[2];
  36   unsigned char n_sectors_s[2];
  37   unsigned char media_byte;
  38   unsigned short sectors_per_fat;
  39   unsigned short sectors_per_track;
  40   unsigned short heads_per_cyl;
  41   unsigned int n_hidden_sectors;
  42   unsigned int n_sectors_l;             /* size of partition */
  43   unsigned char drive_number;
  44   unsigned char mbz;
  45   unsigned char sig_28h;                /* 28h */
  46   unsigned char vol_serno[4];
  47   unsigned char vol_label[11];
  48   unsigned char sig_hpfs[8];            /* "HPFS    " */
  49   unsigned char pad[448];
  50   unsigned short magic;                 /* aa55 */
  51 };
  52 
  53 
  54 /* sector 16 */
  55 
  56 /* The super block has the pointer to the root directory. */
  57 
  58 #define SB_MAGIC 0xf995e849
  59 
  60 struct hpfs_super_block
  61 {
  62   unsigned magic;                       /* f995 e849 */
  63   unsigned magic1;                      /* fa53 e9c5, more magic? */
  64   unsigned huh202;                      /* ?? 202 = N. of B. in 1.00390625 S.*/
  65   fnode_secno root;                     /* fnode of root directory */
  66   secno n_sectors;                      /* size of filesystem */
  67   unsigned n_badblocks;                 /* number of bad blocks */
  68   secno bitmaps;                        /* pointers to free space bit maps */
  69   unsigned zero1;                       /* 0 */
  70   secno badblocks;                      /* bad block list */
  71   unsigned zero3;                       /* 0 */
  72   time_t last_chkdsk;                   /* date last checked, 0 if never */
  73   unsigned zero4;                       /* 0 */
  74   secno n_dir_band;                     /* number of sectors in dir band */
  75   secno dir_band_start;                 /* first sector in dir band */
  76   secno dir_band_end;                   /* last sector in dir band */
  77   secno dir_band_bitmap;                /* free space map, 1 dnode per bit */
  78   unsigned zero5[8];                    /* 0 */
  79   secno scratch_dnodes;                 /* ?? 8 preallocated sectors near dir
  80                                            band, 4-aligned. */
  81   unsigned zero6[103];                  /* 0 */
  82 };
  83 
  84 
  85 /* sector 17 */
  86 
  87 /* The spare block has pointers to spare sectors.  */
  88 
  89 #define SP_MAGIC 0xf9911849
  90 
  91 struct hpfs_spare_block
  92 {
  93   unsigned magic;                       /* f991 1849 */
  94   unsigned magic1;                      /* fa52 29c5, more magic? */
  95 
  96   unsigned dirty: 1;                    /* 0 clean, 1 "improperly stopped" */
  97   unsigned flag1234: 4;                 /* unknown flags */
  98   unsigned fast: 1;                     /* partition was fast formatted */
  99   unsigned flag6to31: 26;               /* unknown flags */
 100 
 101   secno hotfix_map;                     /* info about remapped bad sectors */
 102   unsigned n_spares_used;               /* number of hotfixes */
 103   unsigned n_spares;                    /* number of spares in hotfix map */
 104   unsigned n_dnode_spares_free;         /* spare dnodes unused */
 105   unsigned n_dnode_spares;              /* length of spare_dnodes[] list,
 106                                            follows in this block*/
 107   secno code_page_dir;                  /* code page directory block */
 108   unsigned n_code_pages;                /* number of code pages */
 109   unsigned large_numbers[2];            /* ?? */
 110   unsigned zero1[15];
 111   dnode_secno spare_dnodes[20];         /* emergency free dnode list */
 112   unsigned zero2[81];                   /* room for more? */
 113 };
 114 
 115 /* The bad block list is 4 sectors long.  The first word must be zero,
 116    the remaining words give n_badblocks bad block numbers.
 117    I bet you can see it coming... */
 118 
 119 #define BAD_MAGIC 0
 120        
 121 /* The hotfix map is 4 sectors long.  It looks like
 122 
 123        secno from[n_spares];
 124        secno to[n_spares];
 125 
 126    The to[] list is initialized to point to n_spares preallocated empty
 127    sectors.  The from[] list contains the sector numbers of bad blocks
 128    which have been remapped to corresponding sectors in the to[] list.
 129    n_spares_used gives the length of the from[] list. */
 130 
 131 
 132 /* Sectors 18 and 19 are preallocated and unused.
 133    Maybe they're spares for 16 and 17, but simple substitution fails. */
 134 
 135 
 136 /* The code page info pointed to by the spare block consists of an index
 137    block and blocks containing character maps.  The following is pretty
 138    sketchy, but Linux doesn't use code pages so it doesn't matter. */
 139 
 140 /* block pointed to by spareblock->code_page_dir */
 141 
 142 #define CP_DIR_MAGIC 0x494521f7
 143 
 144 struct code_page_directory
 145 {
 146   unsigned magic;                       /* 4945 21f7 */
 147   unsigned n_code_pages;                /* number of pointers following */
 148   unsigned zero1[2];
 149   struct {
 150     unsigned short ix;                  /* index */
 151     unsigned short code_page_number;    /* code page number */
 152     unsigned bounds;                    /* matches corresponding word
 153                                            in data block */
 154     secno code_page_data;               /* sector number of a code_page_data
 155                                            containing c.p. array */
 156     unsigned index;                     /* index in c.p. array in that sector*/
 157   } array[31];                          /* unknown length */
 158 };
 159 
 160 /* blocks pointed to by code_page_directory */
 161 
 162 #define CP_DATA_MAGIC 0x894521f7
 163 
 164 struct code_page_data
 165 {
 166   unsigned magic;                       /* 8945 21f7 */
 167   unsigned n_used;                      /* # elements used in c_p_data[] */
 168   unsigned bounds[3];                   /* looks a bit like
 169                                              (beg1,end1), (beg2,end2)
 170                                            one byte each */
 171   unsigned short offs[3];               /* offsets from start of sector
 172                                            to start of c_p_data[ix] */
 173   struct {
 174     unsigned short ix;                  /* index */
 175     unsigned short code_page_number;    /* code page number */
 176     unsigned short zero1;
 177     unsigned char map[128];             /* map for chars 80..ff */
 178     unsigned short zero2;
 179   } code_page[3];
 180   unsigned char incognita[78];
 181 };
 182 
 183 
 184 /* Free space bitmaps are 4 sectors long, which is 16384 bits.
 185    16384 sectors is 8 meg, and each 8 meg band has a 4-sector bitmap.
 186    Bit order in the maps is little-endian.  0 means taken, 1 means free.
 187 
 188    Bit map sectors are marked allocated in the bit maps, and so are sectors 
 189    off the end of the partition.
 190 
 191    Band 0 is sectors 0-3fff, its map is in sectors 18-1b.
 192    Band 1 is 4000-7fff, its map is in 7ffc-7fff.
 193    Band 2 is 8000-ffff, its map is in 8000-8003.
 194    The remaining bands have maps in their first (even) or last (odd) 4 sectors
 195      -- if the last, partial, band is odd its map is in its last 4 sectors.
 196 
 197    The bitmap locations are given in a table pointed to by the super block.
 198    No doubt they aren't constrained to be at 18, 7ffc, 8000, ...; that is
 199    just where they usually are.
 200 
 201    The "directory band" is a bunch of sectors preallocated for dnodes.
 202    It has a 4-sector free space bitmap of its own.  Each bit in the map
 203    corresponds to one 4-sector dnode, bit 0 of the map corresponding to
 204    the first 4 sectors of the directory band.  The entire band is marked
 205    allocated in the main bitmap.   The super block gives the locations
 206    of the directory band and its bitmap.  ("band" doesn't mean it is
 207    8 meg long; it isn't.)  */
 208 
 209 
 210 /* dnode: directory.  4 sectors long */
 211 
 212 /* A directory is a tree of dnodes.  The fnode for a directory
 213    contains one pointer, to the root dnode of the tree.  The fnode
 214    never moves, the dnodes do the B-tree thing, splitting and merging
 215    as files are added and removed.  */
 216 
 217 #define DNODE_MAGIC   0x77e40aae
 218 
 219 struct dnode {
 220   unsigned magic;                       /* 77e4 0aae */
 221   unsigned first_free;                  /* offset from start of dnode to
 222                                            first free dir entry */
 223   unsigned increment_me;                /* some kind of activity counter?
 224                                            Neither HPFS.IFS nor CHKDSK cares
 225                                            if you change this word */
 226   secno up;                             /* (root dnode) directory's fnode
 227                                            (nonroot) parent dnode */
 228   dnode_secno self;                     /* pointer to this dnode */
 229   unsigned char dirent[2028];           /* one or more dirents */
 230 };
 231 
 232 struct hpfs_dirent {
 233   unsigned short length;                /* offset to next dirent */
 234   unsigned first: 1;                    /* set on phony ^A^A (".") entry */
 235   unsigned flag1: 1;
 236   unsigned down: 1;                     /* down pointer present (after name) */
 237   unsigned last: 1;                     /* set on phony \377 entry */
 238   unsigned flag4: 1;
 239   unsigned flag5: 1;
 240   unsigned flag6: 1;
 241   unsigned has_needea: 1;               /* ?? some EA has NEEDEA set
 242                                            I have no idea why this is
 243                                            interesting in a dir entry */
 244   unsigned read_only: 1;                /* dos attrib */
 245   unsigned hidden: 1;                   /* dos attrib */
 246   unsigned system: 1;                   /* dos attrib */
 247   unsigned flag11: 1;                   /* would be volume label dos attrib */
 248   unsigned directory: 1;                /* dos attrib */
 249   unsigned archive: 1;                  /* dos attrib */
 250   unsigned not_8x3: 1;                  /* name is not 8.3 */
 251   unsigned flag15: 1;
 252   fnode_secno fnode;                    /* fnode giving allocation info */
 253   time_t write_date;                    /* mtime */
 254   unsigned file_size;                   /* file length, bytes */
 255   time_t read_date;                     /* atime */
 256   time_t creation_date;                 /* ctime */
 257   unsigned ea_size;                     /* total EA length, bytes */
 258   unsigned char zero1;
 259   unsigned char locality;               /* 0=unk 1=seq 2=random 3=both */
 260   unsigned char namelen, name[1];       /* file name */
 261   /* dnode_secno down;    btree down pointer, if present,
 262                           follows name on next word boundary, or maybe it's
 263                           precedes next dirent, which is on a word boundary. */
 264 };
 265 
 266 /* The b-tree down pointer from a dir entry */
 267 
 268 static inline dnode_secno de_down_pointer (struct hpfs_dirent *de)
     /* [previous][next][first][last][top][bottom][index][help] */
 269 {
 270   return *(dnode_secno *) ((void *) de + de->length - 4);
 271 }
 272 
 273 /* The first dir entry in a dnode */
 274 
 275 static inline struct hpfs_dirent *dnode_first_de (struct dnode *dnode)
     /* [previous][next][first][last][top][bottom][index][help] */
 276 {
 277   return (void *) dnode->dirent;
 278 }
 279 
 280 /* The end+1 of the dir entries */
 281 
 282 static inline struct hpfs_dirent *dnode_end_de (struct dnode *dnode)
     /* [previous][next][first][last][top][bottom][index][help] */
 283 {
 284   return (void *) dnode + dnode->first_free;
 285 }
 286 
 287 /* The dir entry after dir entry de */
 288 
 289 static inline struct hpfs_dirent *de_next_de (struct hpfs_dirent *de)
     /* [previous][next][first][last][top][bottom][index][help] */
 290 {
 291   return (void *) de + de->length;
 292 }
 293 
 294 
 295 /* B+ tree: allocation info in fnodes and anodes */
 296 
 297 /* dnodes point to fnodes which are responsible for listing the sectors
 298    assigned to the file.  This is done with trees of (length,address)
 299    pairs.  (Actually triples, of (length, file-address, disk-address)
 300    which can represent holes.  Find out if HPFS does that.)
 301    At any rate, fnodes contain a small tree; if subtrees are needed
 302    they occupy essentially a full block in anodes.  A leaf-level tree node
 303    has 3-word entries giving sector runs, a non-leaf node has 2-word
 304    entries giving subtree pointers.  A flag in the header says which. */
 305 
 306 struct bplus_leaf_node
 307 {
 308   unsigned file_secno;                  /* first file sector in extent */
 309   unsigned length;                      /* length, sectors */
 310   secno disk_secno;                     /* first corresponding disk sector */
 311 };
 312 
 313 struct bplus_internal_node
 314 {
 315   unsigned file_secno;                  /* subtree maps sectors < this  */
 316   anode_secno down;                     /* pointer to subtree */
 317 };
 318 
 319 struct bplus_header
 320 {
 321   unsigned flag0: 1;
 322   unsigned flag1: 1;
 323   unsigned flag2: 1;
 324   unsigned flag3: 1;
 325   unsigned flag4: 1;
 326   unsigned fnode_parent: 1;             /* ? we're pointed to by an fnode,
 327                                            the data btree or some ea or the
 328                                            main ea bootage pointer ea_secno */
 329                                         /* also can get set in fnodes, which
 330                                            may be a chkdsk glitch or may mean
 331                                            this bit is irrelevant in fnodes,
 332                                            or this interpretation is all wet */
 333   unsigned flag6: 1;
 334   unsigned internal: 1;                 /* 1 -> (internal) tree of anodes
 335                                            0 -> (leaf) list of extents */
 336   unsigned char fill[3];
 337   unsigned char n_free_nodes;           /* free nodes in following array */
 338   unsigned char n_used_nodes;           /* used nodes in following array */
 339   unsigned short first_free;            /* offset from start of header to
 340                                            first free node in array */
 341   union {
 342     struct bplus_internal_node internal[0]; /* (internal) 2-word entries giving
 343                                                subtree pointers */
 344     struct bplus_leaf_node external[0];     /* (external) 3-word entries giving
 345                                                sector runs */
 346   } u;
 347 };
 348 
 349 /* fnode: root of allocation b+ tree, and EA's */
 350 
 351 /* Every file and every directory has one fnode, pointed to by the directory
 352    entry and pointing to the file's sectors or directory's root dnode.  EA's
 353    are also stored here, and there are said to be ACL's somewhere here too. */
 354 
 355 #define FNODE_MAGIC 0xf7e40aae
 356 
 357 struct fnode
 358 {
 359   unsigned magic;                       /* f7e4 0aae */
 360   unsigned zero1[2];
 361   unsigned char len, name[15];          /* true length, truncated name */
 362   fnode_secno up;                       /* pointer to file's directory fnode */
 363   unsigned zero2[3];
 364   unsigned ea_size_l;                   /* length of disk-resident ea's */
 365   secno ea_secno;                       /* first sector of disk-resident ea's*/
 366   unsigned short ea_size_s;             /* length of fnode-resident ea's */
 367 
 368   unsigned flag0: 1;
 369   unsigned ea_anode: 1;                 /* 1 -> ea_secno is an anode */
 370   unsigned flag2: 1;
 371   unsigned flag3: 1;
 372   unsigned flag4: 1;
 373   unsigned flag5: 1;
 374   unsigned flag6: 1;
 375   unsigned flag7: 1;
 376   unsigned dirflag: 1;                  /* 1 -> directory.  first & only extent
 377                                            points to dnode. */
 378   unsigned flag9: 1;
 379   unsigned flag10: 1;
 380   unsigned flag11: 1;
 381   unsigned flag12: 1;
 382   unsigned flag13: 1;
 383   unsigned flag14: 1;
 384   unsigned flag15: 1;
 385 
 386   struct bplus_header btree;            /* b+ tree, 8 extents or 12 subtrees */
 387   union {
 388     struct bplus_leaf_node external[8];
 389     struct bplus_internal_node internal[12];
 390   } u;
 391 
 392   unsigned file_size;                   /* file length, bytes */
 393   unsigned n_needea;                    /* number of EA's with NEEDEA set */
 394   unsigned zero4[4];
 395   unsigned ea_offs;                     /* offset from start of fnode
 396                                            to first fnode-resident ea */
 397   unsigned zero5[2];
 398   unsigned char ea[316];                /* zero or more EA's, packed together
 399                                            with no alignment padding.
 400                                            (Do not use this name, get here
 401                                            via fnode + ea_offs. I think.) */
 402 };
 403 
 404 
 405 /* anode: 99.44% pure allocation tree */
 406 
 407 #define ANODE_MAGIC 0x37e40aae
 408 
 409 struct anode
 410 {
 411   unsigned magic;                       /* 37e4 0aae */
 412   anode_secno self;                     /* pointer to this anode */
 413   secno up;                             /* parent anode or fnode */
 414 
 415   struct bplus_header btree;            /* b+tree, 40 extents or 60 subtrees */
 416   union {
 417     struct bplus_leaf_node external[40];
 418     struct bplus_internal_node internal[60];
 419   } u;
 420 
 421   unsigned fill[3];                     /* unused */
 422 };
 423 
 424 
 425 /* extended attributes.
 426 
 427    A file's EA info is stored as a list of (name,value) pairs.  It is
 428    usually in the fnode, but (if it's large) it is moved to a single
 429    sector run outside the fnode, or to multiple runs with an anode tree
 430    that points to them.
 431 
 432    The value of a single EA is stored along with the name, or (if large)
 433    it is moved to a single sector run, or multiple runs pointed to by an
 434    anode tree, pointed to by the value field of the (name,value) pair.
 435 
 436    Flags in the EA tell whether the value is immediate, in a single sector
 437    run, or in multiple runs.  Flags in the fnode tell whether the EA list
 438    is immediate, in a single run, or in multiple runs. */
 439 
 440 struct extended_attribute
 441 {
 442   unsigned indirect: 1;                 /* 1 -> value gives sector number
 443                                            where real value starts */
 444   unsigned anode: 1;                    /* 1 -> sector is an anode
 445                                            that points to fragmented value */
 446   unsigned flag2: 1;
 447   unsigned flag3: 1;
 448   unsigned flag4: 1;
 449   unsigned flag5: 1;
 450   unsigned flag6: 1;
 451   unsigned needea: 1;                   /* required ea */
 452   unsigned char namelen;                /* length of name, bytes */
 453   unsigned short valuelen;              /* length of value, bytes */
 454   /*
 455     unsigned char name[namelen];        ascii attrib name
 456     unsigned char nul;                  terminating '\0', not counted
 457     unsigned char value[valuelen];      value, arbitrary
 458       if this.indirect, valuelen is 8 and the value is
 459         unsigned length;                real length of value, bytes
 460         secno secno;                    sector address where it starts
 461       if this.anode, the above sector number is the root of an anode tree
 462         which points to the value.
 463   */
 464 };
 465 
 466 static inline unsigned char *ea_name (struct extended_attribute *ea)
     /* [previous][next][first][last][top][bottom][index][help] */
 467 {
 468   return (void *) ea + sizeof *ea;
 469 }
 470 
 471 static inline unsigned char *ea_value (struct extended_attribute *ea)
     /* [previous][next][first][last][top][bottom][index][help] */
 472 {
 473   return (void *) ea + sizeof *ea + ea->namelen + 1;
 474 }
 475 
 476 static inline struct extended_attribute *
 477     ea_next_ea (struct extended_attribute *ea)
     /* [previous][next][first][last][top][bottom][index][help] */
 478 {
 479   return (void *) ea + sizeof *ea + ea->namelen + 1 + ea->valuelen;
 480 }
 481 
 482 static inline unsigned ea_indirect_length (struct extended_attribute *ea)
     /* [previous][next][first][last][top][bottom][index][help] */
 483 {
 484   unsigned *v = (void *) ea_value (ea);
 485   return v[0];
 486 }
 487 
 488 static inline secno ea_indirect_secno (struct extended_attribute *ea)
     /* [previous][next][first][last][top][bottom][index][help] */
 489 {
 490   unsigned *v = (void *) ea_value (ea);
 491   return v[1];
 492 }
 493 
 494 /*
 495    Local Variables:
 496    comment-column: 40
 497    End:
 498 */

/* [previous][next][first][last][top][bottom][index][help] */