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  1. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  2. ;;                                                              ;;
  3. ;; Copyright (C) KolibriOS team 2011-2014. All rights reserved. ;;
  4. ;; Distributed under terms of the GNU General Public License    ;;
  5. ;;                                                              ;;
  6. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  7.  
  8. $Revision: 5089 $
  9.  
  10. ; =============================================================================
  11. ; ================================= Constants =================================
  12. ; =============================================================================
  13. ; Error codes for callback functions.
  14. DISK_STATUS_OK              = 0 ; success
  15. DISK_STATUS_GENERAL_ERROR   = -1; if no other code is suitable
  16. DISK_STATUS_INVALID_CALL    = 1 ; invalid input parameters
  17. DISK_STATUS_NO_MEDIA        = 2 ; no media present
  18. DISK_STATUS_END_OF_MEDIA    = 3 ; end of media while reading/writing data
  19. DISK_STATUS_NO_MEMORY       = 4 ; insufficient memory for driver operation
  20. ; Driver flags. Represent bits in DISK.DriverFlags.
  21. DISK_NO_INSERT_NOTIFICATION = 1
  22. ; Media flags. Represent bits in DISKMEDIAINFO.Flags.
  23. DISK_MEDIA_READONLY = 1
  24.  
  25. ; If too many partitions are detected,there is probably an error on the disk.
  26. ; 256 partitions should be enough for any reasonable use.
  27. ; Also, the same number is limiting the number of MBRs to process; if
  28. ; too many MBRs are visible,there probably is a loop in the MBR structure.
  29. MAX_NUM_PARTITIONS = 256
  30.  
  31. ; =============================================================================
  32. ; ================================ Structures =================================
  33. ; =============================================================================
  34. ; This structure defines all callback functions for working with the physical
  35. ; device. They are implemented by a driver. Objects with this structure reside
  36. ; in a driver.
  37. struct  DISKFUNC
  38.         strucsize       dd ?
  39. ; Size of the structure. This field is intended for possible extensions of
  40. ; this structure. If a new function is added to this structure and a driver
  41. ; implements an old version, the caller can detect this by checking .strucsize,
  42. ; so the driver remains compatible.
  43.         close           dd ?
  44. ; The pointer to the function which frees all driver-specific resources for
  45. ; the disk.
  46. ; Optional, may be NULL.
  47. ; void close(void* userdata);
  48.         closemedia      dd ?
  49. ; The pointer to the function which informs the driver that the kernel has
  50. ; finished all processing with the current media. If media is removed, the
  51. ; driver should decline all requests to that media with DISK_STATUS_NO_MEDIA,
  52. ; even if new media is inserted, until this function is called. If media is
  53. ; removed, a new call to 'disk_media_changed' is not allowed until this
  54. ; function is called.
  55. ; Optional, may be NULL (if media is not removable).
  56. ; void closemedia(void* userdata);
  57.         querymedia      dd ?
  58. ; The pointer to the function which determines capabilities of the media.
  59. ; int querymedia(void* userdata, DISKMEDIAINFO* info);
  60. ; Return value: one of DISK_STATUS_*
  61.         read            dd ?
  62. ; The pointer to the function which reads data from the device.
  63. ; int read(void* userdata, void* buffer, __int64 startsector, int* numsectors);
  64. ; input: *numsectors = number of sectors to read
  65. ; output: *numsectors = number of sectors which were successfully read
  66. ; Return value: one of DISK_STATUS_*
  67.         write           dd ?
  68. ; The pointer to the function which writes data to the device.
  69. ; Optional, may be NULL.
  70. ; int write(void* userdata, void* buffer, __int64 startsector, int* numsectors);
  71. ; input: *numsectors = number of sectors to write
  72. ; output: *numsectors = number of sectors which were successfully written
  73. ; Return value: one of DISK_STATUS_*
  74.         flush           dd ?
  75. ; The pointer to the function which flushes the internal device cache.
  76. ; Optional, may be NULL.
  77. ; int flush(void* userdata);
  78. ; Return value: one of DISK_STATUS_*
  79. ; Note that read/write are called by the cache manager, so a driver should not
  80. ; create a software cache. This function is implemented for flushing a hardware
  81. ; cache, if it exists.
  82.         adjust_cache_size       dd ?
  83. ; The pointer to the function which returns the cache size for this device.
  84. ; Optional, may be NULL.
  85. ; unsigned int adjust_cache_size(unsigned int suggested_size);
  86. ; Return value: 0 = disable cache, otherwise = used cache size in bytes.
  87. ends
  88.  
  89. ; This structure holds information on a medium.
  90. ; Objects with this structure are allocated by the kernel as a part of the DISK
  91. ; structure and are filled by a driver in the 'querymedia' callback.
  92. struct  DISKMEDIAINFO
  93.         Flags           dd ?
  94. ; Combination of DISK_MEDIA_* bits.
  95.         SectorSize      dd ?
  96. ; Size of the sector.
  97.         Capacity        dq ?
  98. ; Size of the media in sectors.
  99. ends
  100.  
  101. ; This structure represents the disk cache. To follow the old implementation,
  102. ; there are two distinct caches for a disk, one for "system" data,and the other
  103. ; for "application" data.
  104. struct  DISKCACHE
  105. ; The following fields are inherited from data32.inc:cache_ideX.
  106.         pointer         dd ?
  107.         data_size       dd ?    ; unused
  108.         data            dd ?
  109.         sad_size        dd ?
  110.         search_start    dd ?
  111.         sector_size_log dd ?
  112. ends
  113.  
  114. ; This structure represents a disk device and its media for the kernel.
  115. ; This structure is allocated by the kernel in the 'disk_add' function,
  116. ; freed in the 'disk_dereference' function.
  117. struct  DISK
  118. ; Fields of disk object
  119.         Next            dd ?
  120.         Prev            dd ?
  121. ; All disk devices are linked in one list with these two fields.
  122. ; Head of the list is the 'disk_list' variable.
  123.         Functions       dd ?
  124. ; Pointer to the 'DISKFUNC' structure with driver functions.
  125.         Name            dd ?
  126. ; Pointer to the string used for accesses through the global filesystem.
  127.         UserData        dd ?
  128. ; This field is passed to all callback functions so a driver can decide which
  129. ; physical device is addressed.
  130.         DriverFlags     dd ?
  131. ; Bitfield. Currently only DISK_NO_INSERT_NOTIFICATION bit is defined.
  132. ; If it is set, the driver will never issue 'disk_media_changed' notification
  133. ; with argument set to true, so the kernel must try to detect media during
  134. ; requests from the file system.
  135.         RefCount        dd ?
  136. ; Count of active references to this structure. One reference is kept during
  137. ; the lifetime of the structure between 'disk_add' and 'disk_del'.
  138. ; Another reference is taken during any filesystem operation for this disk.
  139. ; One reference is added if media is inserted.
  140. ; The structure is destroyed when the reference count decrements to zero:
  141. ; this usually occurs in 'disk_del', but can be delayed to the end of last
  142. ; filesystem operation, if one is active.
  143.         MediaLock       MUTEX
  144. ; Lock to protect the MEDIA structure. See the description after
  145. ; 'disk_list_mutex' for the locking strategy.
  146. ; Fields of media object
  147.         MediaInserted   db ?
  148. ; 0 if media is not inserted, nonzero otherwise.
  149.         MediaUsed       db ?
  150. ; 0 if media fields are not used, nonzero otherwise. If .MediaRefCount is
  151. ; nonzero, this field is nonzero too; however, when .MediaRefCount goes
  152. ; to zero, there is some time interval during which media object is still used.
  153.                         dw ? ; padding
  154. ; The following fields are not valid unless either .MediaInserted is nonzero
  155. ; or they are accessed from a code which has obtained the reference when
  156. ; .MediaInserted was nonzero.
  157.         MediaRefCount   dd ?
  158. ; Count of active references to the media object. One reference is kept during
  159. ; the lifetime of the media between two calls to 'disk_media_changed'.
  160. ; Another reference is taken during any filesystem operation for this media.
  161. ; The callback 'closemedia' is called when the reference count decrements to
  162. ; zero: this usually occurs in 'disk_media_changed', but can be delayed to the
  163. ; end of the last filesystem operation, if one is active.
  164.         MediaInfo       DISKMEDIAINFO
  165. ; This field keeps information on the current media.
  166.         NumPartitions   dd ?
  167. ; Number of partitions on this media.
  168.         Partitions      dd ?
  169. ; Pointer to array of .NumPartitions pointers to PARTITION structures.
  170.         cache_size      dd ?
  171. ; inherited from cache_ideX_size
  172.         CacheLock       MUTEX
  173. ; Lock to protect both caches.
  174.         SysCache        DISKCACHE
  175.         AppCache        DISKCACHE
  176. ; Two caches for the disk.
  177. ends
  178.  
  179. ; This structure represents one partition for the kernel. This is a base
  180. ; template, the actual contents after common fields is determined by the
  181. ; file system code for this partition.
  182. struct  PARTITION
  183.         FirstSector     dq ?
  184. ; First sector of the partition.
  185.         Length          dq ?
  186. ; Length of the partition in sectors.
  187.         Disk            dd ?
  188. ; Pointer to parent DISK structure.
  189.         FSUserFunctions dd ?
  190. ; Handlers for the sysfunction 70h. This field is a pointer to the following
  191. ; array. The first dword is pointer to disconnect handler.
  192. ; The first dword is a number of supported subfunctions, other dwords
  193. ; point to handlers of corresponding subfunctions.
  194. ; ...fs-specific data may follow...
  195. ends
  196.  
  197. ; This is an external structure, it represents an entry in the partition table.
  198. struct  PARTITION_TABLE_ENTRY
  199.         Bootable        db ?
  200. ; 80h = bootable partition, 0 = non-bootable partition, other values = invalid
  201.         FirstHead       db ?
  202.         FirstSector     db ?
  203.         FirstTrack      db ?
  204. ; Coordinates of first sector in CHS.
  205.         Type            db ?
  206. ; Partition type, one of predefined constants. 0 = empty, several types denote
  207. ; extended partition (see process_partition_table_entry), we are not interested
  208. ; in other values.
  209.         LastHead        db ?
  210.         LastSector      db ?
  211.         LastTrack       db ?
  212. ; Coordinates of last sector in CHS.
  213.         FirstAbsSector  dd ?
  214. ; Coordinate of first sector in LBA.
  215.         Length          dd ?
  216. ; Length of the partition in sectors.
  217. ends
  218.  
  219. ; =============================================================================
  220. ; ================================ Global data ================================
  221. ; =============================================================================
  222. iglobal
  223. ; The pseudo-item for the list of all DISK structures.
  224. ; Initialized to the empty list.
  225. disk_list:
  226.         dd      disk_list
  227.         dd      disk_list
  228. endg
  229. uglobal
  230. ; This mutex guards all operations with the global list of DISK structures.
  231. disk_list_mutex MUTEX
  232. ; * There are two dependent objects, a disk and a media. In the simplest case,
  233. ;   disk and media are both non-removable. However, in the general case both
  234. ;   can be removed at any time, simultaneously or only media,and this makes things
  235. ;   complicated.
  236. ; * For efficiency, both disk and media objects are located in the one
  237. ;   structure named DISK. However, logically they are different.
  238. ; * The following operations use data of disk object: adding (disk_add);
  239. ;   deleting (disk_del); filesystem (fs_lfn which eventually calls
  240. ;   dyndisk_handler or dyndisk_enum_root).
  241. ; * The following operations use data of media object: adding/removing
  242. ;   (disk_media_changed); filesystem (fs_lfn which eventually calls
  243. ;   dyndisk_handler; dyndisk_enum_root doesn't work with media).
  244. ; * Notifications disk_add, disk_media_changed, disk_del are synchronized
  245. ;   between themselves, this is a requirement for the driver. However, file
  246. ;   system operations are asynchronous, can be issued at any time by any
  247. ;   thread.
  248. ; * We must prevent a situation when a filesystem operation thinks that the
  249. ;   object is still valid but in fact the notification has destroyed the
  250. ;   object. So we keep a reference counter for both disk and media and destroy
  251. ;   the object when this counter goes to zero.
  252. ; * The driver must know when it is safe to free driver-allocated resources.
  253. ;   The object can be alive even after death notification has completed.
  254. ;   We use special callbacks to satisfy both assertions: 'close' for the disk
  255. ;   and 'closemedia' for the media. The destruction of the object includes
  256. ;   calling the corresponding callback.
  257. ; * Each filesystem operation keeps one reference for the disk and one
  258. ;   reference for the media. Notification disk_del forces notification on the
  259. ;   media death, so the reference counter for the disk is always not less than
  260. ;   the reference counter for the media.
  261. ; * Two operations "get the object" and "increment the reference counter" can
  262. ;   not be done simultaneously. We use a mutex to guard the consistency here.
  263. ;   It must be a part of the container for the object, so that this mutex can
  264. ;   be acquired as a part of getting the object from the container. The
  265. ;   container for disk object is the global list, and this list is guarded by
  266. ;   'disk_list_mutex'. The container for media object is the disk object, and
  267. ;   the corresponding mutex is DISK.MediaLock.
  268. ; * Notifications do not change the data of objects, they can only remove
  269. ;   objects. Thus we don't need another synchronization at this level. If two
  270. ;   filesystem operations are referencing the same filesystem data, this is
  271. ;   better resolved at the level of the filesystem.
  272. endg
  273.  
  274. iglobal
  275. ; The function 'disk_scan_partitions' needs three sector-sized buffers for
  276. ; MBR, bootsector and fs-temporary sector data. It can not use the static
  277. ; buffers always, since it can be called for two or more disks in parallel.
  278. ; However, this case is not typical. We reserve three static 512-byte buffers
  279. ; and a flag that these buffers are currently used. If 'disk_scan_partitions'
  280. ; detects that the buffers are currently used, it allocates buffers from the
  281. ; heap. Also, the heap is used when sector size is other than 512.
  282. ; The flag is implemented as a global dword variable. When the static buffers
  283. ; are not used, the value is -1. When the static buffers are used, the value
  284. ; is normally 0 and temporarily can become greater. The function increments
  285. ; this value. If the resulting value is zero, it uses the buffers and
  286. ; decrements the value when the job is done. Otherwise, it immediately
  287. ; decrements the value and uses buffers from the heap, allocated in the
  288. ; beginning and freed in the end.
  289. partition_buffer_users  dd      -1
  290. endg
  291. uglobal
  292. ; The static buffers for MBR, bootsector and fs-temporary sector data.
  293. align 16
  294. mbr_buffer      rb      512
  295. bootsect_buffer rb      512
  296. fs_tmp_buffer   rb      512
  297. endg
  298.  
  299. iglobal
  300. ; This is the array of default implementations of driver callbacks.
  301. ; Same as DRIVERFUNC structure except for the first field; all functions must
  302. ; have the default implementations.
  303. align 4
  304. disk_default_callbacks:
  305.         dd      disk_default_close
  306.         dd      disk_default_closemedia
  307.         dd      disk_default_querymedia
  308.         dd      disk_default_read
  309.         dd      disk_default_write
  310.         dd      disk_default_flush
  311.         dd      disk_default_adjust_cache_size
  312. endg
  313.  
  314. ; =============================================================================
  315. ; ================================= Functions =================================
  316. ; =============================================================================
  317.  
  318. ; This function registers a disk device.
  319. ; This includes:
  320. ; - allocating an internal structure describing this device;
  321. ; - registering this structure in the global filesystem.
  322. ; The function initializes the disk as if there is no media. If a media is
  323. ; present, the function 'disk_media_changed' should be called after this
  324. ; function succeeds.
  325. ; Parameters:
  326. ; [esp+4] = pointer to DISKFUNC structure with the callbacks
  327. ; [esp+8] = pointer to name (ASCIIZ string)
  328. ; [esp+12] = userdata to be passed to the callbacks as is.
  329. ; [esp+16] = flags, bitfield. Currently only DISK_NO_INSERT_NOTIFICATION bit
  330. ;            is defined.
  331. ; Return value:
  332. ; NULL = operation has failed
  333. ; non-NULL = handle of the disk. This handle can be used
  334. ; in the operations with other Disk* functions.
  335. ; The handle is the pointer to the internal structure DISK.
  336. disk_add:
  337.         push    ebx esi         ; save used registers to be stdcall
  338. ; 1. Allocate the DISK structure.
  339. ; 1a. Call the heap manager.
  340.         movi    eax, sizeof.DISK
  341.         call    malloc
  342. ; 1b. Check the result. If allocation failed, return (go to 9) with eax = 0.
  343.         test    eax, eax
  344.         jz      .nothing
  345. ; 2. Copy the disk name to the DISK structure.
  346. ; 2a. Get length of the name, including the terminating zero.
  347.         mov     ebx, [esp+8+8]  ; ebx = pointer to name
  348.         push    eax             ; save allocated pointer to DISK
  349.         xor     eax, eax        ; the argument of malloc() is in eax
  350. @@:
  351.         inc     eax
  352.         cmp     byte [ebx+eax-1], 0
  353.         jnz     @b
  354. ; 2b. Call the heap manager.
  355.         call    malloc
  356. ; 2c. Check the result. If allocation failed, go to 7.
  357.         pop     esi             ; restore allocated pointer to DISK
  358.         test    eax, eax
  359.         jz      .free
  360. ; 2d. Store the allocated pointer to the DISK structure.
  361.         mov     [esi+DISK.Name], eax
  362. ; 2e. Copy the name.
  363. @@:
  364.         mov     dl, [ebx]
  365.         mov     [eax], dl
  366.         inc     ebx
  367.         inc     eax
  368.         test    dl, dl
  369.         jnz     @b
  370. ; 3. Copy other arguments of the function to the DISK structure.
  371.         mov     eax, [esp+4+8]
  372.         mov     [esi+DISK.Functions], eax
  373.         mov     eax, [esp+12+8]
  374.         mov     [esi+DISK.UserData], eax
  375.         mov     eax, [esp+16+8]
  376.         mov     [esi+DISK.DriverFlags], eax
  377. ; 4. Initialize other fields of the DISK structure.
  378. ; Media is not inserted, reference counter is 1.
  379.         lea     ecx, [esi+DISK.MediaLock]
  380.         call    mutex_init
  381.         xor     eax, eax
  382.         mov     dword [esi+DISK.MediaInserted], eax
  383.         mov     [esi+DISK.MediaRefCount], eax
  384.         inc     eax
  385.         mov     [esi+DISK.RefCount], eax
  386. ; The DISK structure is initialized.
  387. ; 5. Insert the new structure to the global list.
  388. ; 5a. Acquire the mutex.
  389.         mov     ecx, disk_list_mutex
  390.         call    mutex_lock
  391. ; 5b. Insert item to the tail of double-linked list.
  392.         mov     edx, disk_list
  393.         list_add_tail esi, edx     ;esi= new edx= list head
  394. ; 5c. Release the mutex.
  395.         call    mutex_unlock
  396. ; 6. Return with eax = pointer to DISK.
  397.         xchg    eax, esi
  398.         jmp     .nothing
  399. .free:
  400. ; Memory allocation for DISK structure succeeded, but for disk name failed.
  401. ; 7. Free the DISK structure.
  402.         xchg    eax, esi
  403.         call    free
  404. ; 8. Return with eax = 0.
  405.         xor     eax, eax
  406. .nothing:
  407. ; 9. Return.
  408.         pop     esi ebx         ; restore used registers to be stdcall
  409.         ret     16              ; purge 4 dword arguments to be stdcall
  410.  
  411. ; This function deletes a disk device from the global filesystem.
  412. ; This includes:
  413. ; - removing a media including all partitions;
  414. ; - deleting this structure from the global filesystem;
  415. ; - dereferencing the DISK structure and possibly destroying it.
  416. ; Parameters:
  417. ; [esp+4] = handle of the disk, i.e. the pointer to the DISK structure.
  418. ; Return value: none.
  419. disk_del:
  420.         push    esi         ; save used registers to be stdcall
  421. ; 1. Force media to be removed. If the media is already removed, the
  422. ; call does nothing.
  423.         mov     esi, [esp+4+4]  ; esi = handle of the disk
  424.         stdcall disk_media_changed, esi, 0
  425. ; 2. Delete the structure from the global list.
  426. ; 2a. Acquire the mutex.
  427.         mov     ecx, disk_list_mutex
  428.         call    mutex_lock
  429. ; 2b. Delete item from double-linked list.
  430.         mov     eax, [esi+DISK.Next]
  431.         mov     edx, [esi+DISK.Prev]
  432.         mov     [eax+DISK.Prev], edx
  433.         mov     [edx+DISK.Next], eax
  434. ; 2c. Release the mutex.
  435.         call    mutex_unlock
  436. ; 3. The structure still has one reference created in disk_add. Remove this
  437. ; reference. If there are no other references, disk_dereference will free the
  438. ; structure.
  439.         call    disk_dereference
  440. ; 4. Return.
  441.         pop     esi             ; restore used registers to be stdcall
  442.         ret     4               ; purge 1 dword argument to be stdcall
  443.  
  444. ; This is an internal function which removes a previously obtained reference
  445. ; to the disk. If this is the last reference, this function lets the driver
  446. ; finalize all associated data, and afterwards frees the DISK structure.
  447. ; esi = pointer to DISK structure
  448. disk_dereference:
  449. ; 1. Decrement reference counter. Use atomic operation to correctly handle
  450. ; possible simultaneous calls.
  451.         lock dec [esi+DISK.RefCount]
  452. ; 2. If the result is nonzero, there are other references, so nothing to do.
  453. ; In this case, return (go to 4).
  454.         jnz     .nothing
  455. ; 3. If we are here, we just removed the last reference and must destroy the
  456. ; disk object.
  457. ; 3a. Call the driver.
  458.         mov     al, DISKFUNC.close
  459.         stdcall disk_call_driver
  460. ; 3b. Free the structure.
  461.         xchg    eax, esi
  462.         push    ebx
  463.         call    free
  464.         pop     ebx
  465. ; 4. Return.
  466. .nothing:
  467.         ret
  468.  
  469. ; This is an internal function which removes a previously obtained reference
  470. ; to the media. If this is the last reference, this function calls 'closemedia'
  471. ; callback to signal the driver that the processing has finished and it is safe
  472. ; to inform about a new media.
  473. ; esi = pointer to DISK structure
  474. disk_media_dereference:
  475. ; 1. Decrement reference counter. Use atomic operation to correctly handle
  476. ; possible simultaneous calls.
  477.         lock dec [esi+DISK.MediaRefCount]
  478. ; 2. If the result is nonzero, there are other references, so nothing to do.
  479. ; In this case, return (go to 4).
  480.         jnz     .nothing
  481. ; 3. If we are here, we just removed the last reference and must destroy the
  482. ; media object.
  483. ; Note that the same place inside the DISK structure is reused for all media
  484. ; objects, so we must guarantee that reusing does not happen while freeing.
  485. ; Reusing is only possible when someone processes a new media. There are two
  486. ; mutually exclusive variants:
  487. ; * driver issues media insert notifications (DISK_NO_INSERT_NOTIFICATION bit
  488. ;   in DISK.DriverFlags is not set). In this case, we require from the driver
  489. ;   that such notification (except for the first one) can occur only after a
  490. ;   call to 'closemedia' callback.
  491. ; * driver does not issue media insert notifications. In this case, the kernel
  492. ;   itself must sometimes check whether media is inserted. We have the flag
  493. ;   DISK.MediaUsed, visible to the kernel. This flag signals to the other parts
  494. ;   of kernel that the way is free.
  495. ; In the first case other parts of the kernel do not use DISK.MediaUsed, so it
  496. ; does not matter when this flag is cleared. In the second case this flag must
  497. ; be cleared after all other actions, including call to 'closemedia'.
  498. ; 3a. Free all partitions.
  499.         push    esi edi
  500.         mov     edi, [esi+DISK.NumPartitions]
  501.         mov     esi, [esi+DISK.Partitions]
  502.         test    edi, edi
  503.         jz      .nofree
  504. .freeloop:
  505.         lodsd
  506.         mov     ecx, [eax+PARTITION.FSUserFunctions]
  507.         call    dword [ecx]
  508.         dec     edi
  509.         jnz     .freeloop
  510. .nofree:
  511.         pop     edi esi
  512. ; 3b. Free the cache.
  513.         call    disk_free_cache
  514. ; 3c. Call the driver.
  515.         mov     al, DISKFUNC.closemedia
  516.         stdcall disk_call_driver
  517. ; 3d. Clear the flag.
  518.         mov     [esi+DISK.MediaUsed], 0
  519. .nothing:
  520.         ret
  521.  
  522. ; This function is called by the driver and informs the kernel that the media
  523. ; has changed. If the media is non-removable, it is called exactly once
  524. ; immediately after 'disk_add' and once from 'disk_del'.
  525. ; Parameters:
  526. ; [esp+4] = handle of the disk, i.e. the pointer to the DISK structure.
  527. ; [esp+8] = new status of the media: zero = no media, nonzero = media inserted.
  528. disk_media_changed:
  529.         push    ebx esi edi             ; save used registers to be stdcall
  530. ; 1. Remove the existing media, if it is present.
  531.         mov     esi, [esp+4+12]         ; esi = pointer to DISK
  532. ; 1a. Check whether it is present. Since DISK.MediaInserted is changed only
  533. ; in this function and calls to this function are synchronized, no lock is
  534. ; required for checking.
  535.         cmp     [esi+DISK.MediaInserted], 0
  536.         jz      .noremove
  537. ; We really need to remove the media.
  538. ; 1b. Acquire mutex.
  539.         lea     ecx, [esi+DISK.MediaLock]
  540.         call    mutex_lock
  541. ; 1c. Clear the flag.
  542.         mov     [esi+DISK.MediaInserted], 0
  543. ; 1d. Release mutex.
  544.         call    mutex_unlock
  545. ; 1e. Remove the "lifetime" reference and possibly destroy the structure.
  546.         call    disk_media_dereference
  547. .noremove:
  548. ; 2. Test whether there is new media.
  549.         cmp     dword [esp+8+12], 0
  550.         jz      .noinsert
  551. ; Yep, there is.
  552. ; 3. Process the new media. We assume that all media fields are available to
  553. ; use, see comments in 'disk_media_dereference' (this covers using by previous
  554. ; media referencers) and note that calls to this function are synchronized
  555. ; (this covers using by new media referencers).
  556. ; 3a. Call the 'querymedia' callback.
  557. ; .Flags are set to zero for possible future extensions.
  558.         lea     edx, [esi+DISK.MediaInfo]
  559.         and     [edx+DISKMEDIAINFO.Flags], 0
  560.         mov     al, DISKFUNC.querymedia
  561.         stdcall disk_call_driver, edx
  562. ; 3b. Check the result of the callback. Abort if it failed.
  563.         test    eax, eax
  564.         jnz     .noinsert
  565. ; 3c. Allocate the cache unless disabled by the driver. Abort if failed.
  566.         call    disk_init_cache
  567.         test    al, al
  568.         jz      .noinsert
  569. ; 3d. Acquire the lifetime reference for the media object.
  570.         inc     [esi+DISK.MediaRefCount]
  571. ; 3e. Scan for partitions. Ignore result; the list of partitions is valid even
  572. ; on errors.
  573.         call    disk_scan_partitions
  574. ; 3f. Media is inserted and available for use.
  575.         inc     [esi+DISK.MediaInserted]
  576. .noinsert:
  577. ; 4. Return.
  578.         pop     edi esi ebx             ; restore used registers to be stdcall
  579.         ret     8                       ; purge 2 dword arguments to be stdcall
  580.  
  581. ; This function is a thunk for all functions of a disk driver.
  582. ; It checks whether the referenced function is implemented in the driver.
  583. ; If so, this function jumps to the function in the driver.
  584. ; Otherwise, it jumps to the default implementation.
  585. ; al = offset of function in the DISKFUNC structure;
  586. ; esi = pointer to the DISK structure;
  587. ; stack is the same as for the corresponding function except that the
  588. ; first parameter (void* userdata) is prepended automatically.
  589. disk_call_driver:
  590.         movzx   eax, al ; eax = offset of function in the DISKFUNC structure
  591. ; 1. Prepend the first argument to the stack.
  592.         pop     ecx     ; ecx = return address
  593.         push    [esi+DISK.UserData]     ; add argument
  594.         push    ecx     ; save return address
  595. ; 2. Check that the required function is inside the table. If not, go to 5.
  596.         mov     ecx, [esi+DISK.Functions]
  597.         cmp     eax, [ecx+DISKFUNC.strucsize]
  598.         jae     .default
  599. ; 3. Check that the required function is implemented. If not, go to 5.
  600.         mov     ecx, [ecx+eax]
  601.         test    ecx, ecx
  602.         jz      .default
  603. ; 4. Jump to the required function.
  604.         jmp     ecx
  605. .default:
  606. ; 5. Driver does not implement the required function; use default implementation.
  607.         jmp     dword [disk_default_callbacks+eax-4]
  608.  
  609. ; The default implementation of DISKFUNC.querymedia.
  610. disk_default_querymedia:
  611.         movi    eax, DISK_STATUS_INVALID_CALL
  612.         ret     8
  613.  
  614. ; The default implementation of DISKFUNC.read and DISKFUNC.write.
  615. disk_default_read:
  616. disk_default_write:
  617.         movi    eax, DISK_STATUS_INVALID_CALL
  618.         ret     20
  619.  
  620. ; The default implementation of DISKFUNC.close, DISKFUNC.closemedia and
  621. ; DISKFUNC.flush.
  622. disk_default_close:
  623. disk_default_closemedia:
  624. disk_default_flush:
  625.         xor     eax, eax
  626.         ret     4
  627.  
  628. ; The default implementation of DISKFUNC.adjust_cache_size.
  629. disk_default_adjust_cache_size:
  630.         mov     eax, [esp+8]
  631.         ret     8
  632.  
  633. ; This is an internal function called from 'disk_media_changed' when a new media
  634. ; is detected. It creates the list of partitions for the media.
  635. ; If media is not partitioned, then the list consists of one partition which
  636. ; covers all the media.
  637. ; esi = pointer to the DISK structure.
  638. disk_scan_partitions:
  639. ; 1. Initialize .NumPartitions and .Partitions fields as zeros: empty list.
  640.         and     [esi+DISK.NumPartitions], 0
  641.         and     [esi+DISK.Partitions], 0
  642. ; 2. Acquire the buffer for MBR and bootsector tests. See the comment before
  643. ; the 'partition_buffer_users' variable.
  644.         mov     eax, [esi+DISK.MediaInfo.SectorSize]
  645.         cmp     eax, 512
  646.         jnz     @f
  647.         mov     ebx, mbr_buffer         ; assume the global buffer is free
  648.         lock inc [partition_buffer_users]
  649.         jz      .buffer_acquired        ; yes, it is free
  650.         lock dec [partition_buffer_users]       ; no, we must allocate
  651. @@:
  652.         lea     eax, [eax*3]
  653.         stdcall kernel_alloc, eax
  654.         test    eax, eax
  655.         jz      .nothing
  656.         xchg    eax, ebx
  657. .buffer_acquired:
  658. ; MBR/EBRs are organized in the chain. We use a loop over MBR/EBRs, but no
  659. ; more than MAX_NUM_PARTITION times.
  660. ; 3. Prepare things for the loop.
  661. ; ebp will hold the sector number for current MBR/EBR.
  662. ; [esp] will hold the sector number for current extended partition, if there
  663. ; is one.
  664. ; [esp+4] will hold the counter that prevents long loops.
  665.         push    ebp             ; save ebp
  666.         push    MAX_NUM_PARTITIONS      ; the counter of max MBRs to process
  667.         xor     ebp, ebp        ; start from sector zero
  668.         push    ebp             ; no extended partition yet
  669. ; 4. MBR is 512 bytes long. If sector size is less than 512 bytes,
  670. ; assume no MBR, no partitions and go to 10.
  671.         cmp     [esi+DISK.MediaInfo.SectorSize], 512
  672.         jb      .notmbr
  673. .new_mbr:
  674. ; 5. Read the current sector.
  675. ; Note that 'read' callback operates with 64-bit sector numbers, so we must
  676. ; push additional zero as a high dword of sector number.
  677.         mov     al, DISKFUNC.read
  678.         push    1
  679.         stdcall disk_call_driver, ebx, ebp, 0, esp
  680.         pop     ecx
  681. ; 6. If the read has failed, abort the loop.
  682.         dec     ecx
  683.         jnz     .mbr_failed
  684. ; 7. Check the MBR/EBR signature. If it is wrong, abort the loop.
  685. ; Soon we will access the partition table which starts at ebx+0x1BE,
  686. ; so we can fill its address right now. If we do it now, then the addressing
  687. ; [ecx+0x40] is shorter than [ebx+0x1fe]: one-byte offset vs 4-bytes offset.
  688.         lea     ecx, [ebx+0x1be]        ; ecx -> partition table
  689.         cmp     word [ecx+0x40], 0xaa55
  690.         jnz     .mbr_failed
  691. ; 8. The MBR is treated differently from EBRs. For MBR we additionally need to
  692. ; execute step 9 and possibly step 10.
  693.         test    ebp, ebp
  694.         jnz     .mbr
  695. ; The partition table can be present or not present. In the first case, we just
  696. ; read the MBR. In the second case, we just read the bootsector for a
  697. ; filesystem.
  698. ; The following algorithm is used to distinguish between these cases.
  699. ; A. If at least one entry of the partition table is invalid, this is
  700. ;    a bootsector. See the description of 'is_partition_table_entry' for
  701. ;    definition of validity.
  702. ; B. If all entries are empty (filesystem type field is zero) and the first
  703. ;    byte is jmp opcode (0EBh or 0E9h), this is a bootsector which happens to
  704. ;    have zeros in the place of partition table.
  705. ; C. Otherwise, this is an MBR.
  706. ; 9. Test for MBR vs bootsector.
  707. ; 9a. Check entries. If any is invalid, go to 10 (rule A).
  708.         call    is_partition_table_entry
  709.         jc      .notmbr
  710.         add     ecx, 10h
  711.         call    is_partition_table_entry
  712.         jc      .notmbr
  713.         add     ecx, 10h
  714.         call    is_partition_table_entry
  715.         jc      .notmbr
  716.         add     ecx, 10h
  717.         call    is_partition_table_entry
  718.         jc      .notmbr
  719. ; 9b. Check types of the entries. If at least one is nonzero, go to 11 (rule C).
  720.         mov     al, [ecx-30h+PARTITION_TABLE_ENTRY.Type]
  721.         or      al, [ecx-20h+PARTITION_TABLE_ENTRY.Type]
  722.         or      al, [ecx-10h+PARTITION_TABLE_ENTRY.Type]
  723.         or      al, [ecx+PARTITION_TABLE_ENTRY.Type]
  724.         jnz     .mbr
  725. ; 9c. Empty partition table or bootsector with many zeroes? (rule B)
  726.         cmp     byte [ebx], 0EBh
  727.         jz      .notmbr
  728.         cmp     byte [ebx], 0E9h
  729.         jnz     .mbr
  730. .notmbr:
  731. ; 10. This is not an  MBR. The media is not partitioned. Create one partition
  732. ; which covers all the media and abort the loop.
  733.         stdcall disk_add_partition, 0, 0, \
  734.                 dword [esi+DISK.MediaInfo.Capacity], dword [esi+DISK.MediaInfo.Capacity+4], esi
  735.         jmp     .done
  736. .mbr:
  737. ; 11. Process all entries of the new MBR/EBR
  738.         lea     ecx, [ebx+0x1be]        ; ecx -> partition table
  739.         push    0       ; assume no extended partition
  740.         call    process_partition_table_entry
  741.         add     ecx, 10h
  742.         call    process_partition_table_entry
  743.         add     ecx, 10h
  744.         call    process_partition_table_entry
  745.         add     ecx, 10h
  746.         call    process_partition_table_entry
  747.         pop     ebp
  748. ; 12. Test whether we found a new EBR and should continue the loop.
  749. ; 12a. If there was no next EBR, return.
  750.         test    ebp, ebp
  751.         jz      .done
  752. ; Ok, we have EBR.
  753. ; 12b. EBRs addresses are relative to the start of extended partition.
  754. ; For simplicity, just abort if an 32-bit overflow occurs; large disks
  755. ; are most likely partitioned with GPT, not MBR scheme, since the precise
  756. ; calculation here would increase limit just twice at the price of big
  757. ; compatibility problems.
  758.         pop     eax     ; load extended partition
  759.         add     ebp, eax
  760.         jc      .mbr_failed
  761. ; 12c. If extended partition has not yet started, start it.
  762.         test    eax, eax
  763.         jnz     @f
  764.         mov     eax, ebp
  765. @@:
  766. ; 12c. If the limit is not exceeded, continue the loop.
  767.         dec     dword [esp]
  768.         push    eax     ; store extended partition
  769.         jnz     .new_mbr
  770. .mbr_failed:
  771. .done:
  772. ; 13. Cleanup after the loop.
  773.         pop     eax     ; not important anymore
  774.         pop     eax     ; not important anymore
  775.         pop     ebp     ; restore ebp
  776. ; 14. Release the buffer.
  777. ; 14a. Test whether it is the global buffer or we have allocated it.
  778.         cmp     ebx, mbr_buffer
  779.         jz      .release_partition_buffer
  780. ; 14b. If we have allocated it, free it.
  781.         xchg    eax, ebx
  782.         call    free
  783.         jmp     .nothing
  784. ; 14c. Otherwise, release reference.
  785. .release_partition_buffer:
  786.         lock dec [partition_buffer_users]
  787. .nothing:
  788. ; 15. Return.
  789.         ret
  790.  
  791. ; This is an internal function called from disk_scan_partitions. It checks
  792. ; whether the entry pointed to by ecx is a valid entry of partition table.
  793. ; The entry is valid if the first byte is 0 or 80h, the first sector plus the
  794. ; length is less than twice the size of media. Multiplication by two is
  795. ; required since the size mentioned in the partition table can be slightly
  796. ; greater than the real size.
  797. is_partition_table_entry:
  798. ; 1. Check .Bootable field.
  799.         mov     al, [ecx+PARTITION_TABLE_ENTRY.Bootable]
  800.         and     al, 7Fh
  801.         jnz     .invalid
  802. ; 3. Calculate first sector + length. Note that .FirstAbsSector is relative
  803. ; to the MBR/EBR, so the real sum is ebp + .FirstAbsSector + .Length.
  804.         mov     eax, ebp
  805.         xor     edx, edx
  806.         add     eax, [ecx+PARTITION_TABLE_ENTRY.FirstAbsSector]
  807.         adc     edx, 0
  808.         add     eax, [ecx+PARTITION_TABLE_ENTRY.Length]
  809.         adc     edx, 0
  810. ; 4. Divide by two.
  811.         shr     edx, 1
  812.         rcr     eax, 1
  813. ; 5. Compare with capacity. If the subtraction (edx:eax) - .Capacity does not
  814. ; overflow, this is bad.
  815.         sub     eax, dword [esi+DISK.MediaInfo.Capacity]
  816.         sbb     edx, dword [esi+DISK.MediaInfo.Capacity+4]
  817.         jnc     .invalid
  818. .valid:
  819. ; 5. Return success: CF is cleared.
  820.         clc
  821.         ret
  822. .invalid:
  823. ; 6. Return fail: CF is set.
  824.         stc
  825.         ret
  826.  
  827. ; This is an internal function called from disk_scan_partitions. It processes
  828. ; the entry pointed to by ecx.
  829. ; * If the entry is invalid, just ignore this entry.
  830. ; * If the type is zero, just ignore this entry.
  831. ; * If the type is one of types for extended partition, store the address
  832. ;   of this partition as the new MBR in [esp+4].
  833. ; * Otherwise, add the partition to the list of partitions for this disk.
  834. ;   We don't use the type from the entry to identify the file system;
  835. ;   fs-specific checks do this more reliably.
  836. process_partition_table_entry:
  837. ; 1. Check for valid entry. If invalid, return (go to 5).
  838.         call    is_partition_table_entry
  839.         jc      .nothing
  840. ; 2. Check for empty entry. If invalid, return (go to 5).
  841.         mov     al, [ecx+PARTITION_TABLE_ENTRY.Type]
  842.         test    al, al
  843.         jz      .nothing
  844. ; 3. Check for extended partition. If extended, go to 6.
  845. irp type,\
  846.     0x05,\                 ; DOS: extended partition
  847.     0x0f,\                 ; WIN95: extended partition, LBA-mapped
  848.     0xc5,\                 ; DRDOS/secured: extended partition
  849.     0xd5                   ; Old Multiuser DOS secured: extended partition
  850. {
  851.         cmp     al, type
  852.         jz      .extended
  853. }
  854. ; 4. If we are here, that is a normal partition. Add it to the list.
  855. ; Note that the first sector is relative to MBR/EBR.
  856.         mov     eax, ebp
  857.         xor     edx, edx
  858.         add     eax, [ecx+PARTITION_TABLE_ENTRY.FirstAbsSector]
  859.         adc     edx, 0
  860.         push    ecx
  861.         stdcall disk_add_partition, eax, edx, \
  862.                 [ecx+PARTITION_TABLE_ENTRY.Length], 0, esi
  863.         pop     ecx
  864. .nothing:
  865. ; 5. Return.
  866.         ret
  867. .extended:
  868. ; 6. If we are here, that is an extended partition. Store the address.
  869.         mov     eax, [ecx+PARTITION_TABLE_ENTRY.FirstAbsSector]
  870.         mov     [esp+4], eax
  871.         ret
  872.  
  873. ; This is an internal function called from disk_scan_partitions and
  874. ; process_partition_table_entry. It adds one partition to the list of
  875. ; partitions for the media.
  876. ; Important note: start, length, disk MUST be present and
  877. ; MUST be in the same order as in PARTITION structure.
  878. ; esi duplicates [disk].
  879. proc disk_add_partition stdcall uses ebx edi, start:qword, length:qword, disk:dword
  880. ; 1. Check that this partition will not exceed the limit on total number.
  881.         cmp     [esi+DISK.NumPartitions], MAX_NUM_PARTITIONS
  882.         jae     .nothing
  883. ; 2. Check that this partition does not overlap with any already registered
  884. ; partition. Since any file system assumes that the disk data will not change
  885. ; outside of its control, such overlap could be destructive.
  886. ; Since the number of partitions is usually very small and is guaranteed not
  887. ; to be large, the simple linear search is sufficient.
  888. ; 2a. Prepare the loop: edi will point to the current item of .Partitions
  889. ; array, ecx will be the current item, ebx will hold number of items left.
  890.         mov     edi, [esi+DISK.Partitions]
  891.         mov     ebx, [esi+DISK.NumPartitions]
  892.         test    ebx, ebx
  893.         jz      .partitionok
  894. .scan_existing:
  895. ; 2b. Get the next partition.
  896.         mov     ecx, [edi]
  897.         add     edi, 4
  898. ; The range [.FirstSector, .FirstSector+.Length) must be either entirely to
  899. ; the left of [start, start+length) or entirely to the right.
  900. ; 2c. Subtract .FirstSector - start. The possible overflow distinguish between
  901. ; cases "to the left" (2e) and "to the right" (2d).
  902.         mov     eax, dword [ecx+PARTITION.FirstSector]
  903.         mov     edx, dword [ecx+PARTITION.FirstSector+4]
  904.         sub     eax, dword [start]
  905.         sbb     edx, dword [start+4]
  906.         jb      .less
  907. ; 2d. .FirstSector is greater than or equal to start. Check that .FirstSector
  908. ; is greater than or equal to start+length; the subtraction
  909. ; (.FirstSector-start) - length must not cause overflow. Go to 2g if life is
  910. ; good or to 2f in the other case.
  911.         sub     eax, dword [length]
  912.         sbb     edx, dword [length+4]
  913.         jb      .overlap
  914.         jmp     .next_existing
  915. .less:
  916. ; 2e. .FirstSector is less than start. Check that .FirstSector+.Length is less
  917. ; than or equal to start. If the addition (.FirstSector-start) + .Length does
  918. ; not cause overflow, then .FirstSector + .Length is strictly less than start;
  919. ; since the equality is also valid, use decrement preliminarily. Go to 2g or
  920. ; 2f depending on the overflow.
  921.         sub     eax, 1
  922.         sbb     edx, 0
  923.         add     eax, dword [ecx+PARTITION.Length]
  924.         adc     edx, dword [ecx+PARTITION.Length+4]
  925.         jnc     .next_existing
  926. .overlap:
  927. ; 2f. The partition overlaps with previously registered partition. Say warning
  928. ; and return with nothing done.
  929.         dbgstr 'two partitions overlap, ignoring the last one'
  930.         jmp     .nothing
  931. .next_existing:
  932. ; 2g. The partition does not overlap with the current partition. Continue the
  933. ; loop.
  934.         dec     ebx
  935.         jnz     .scan_existing
  936. .partitionok:
  937. ; 3. The partition has passed tests. Reallocate the partitions array for a new
  938. ; entry.
  939. ; 3a. Call the allocator.
  940.         mov     eax, [esi+DISK.NumPartitions]
  941.         inc     eax     ; one more entry
  942.         shl     eax, 2  ; each entry is dword
  943.         call    malloc
  944. ; 3b. Test the result. If failed, return with nothing done.
  945.         test    eax, eax
  946.         jz      .nothing
  947. ; 3c. Copy the old array to the new array.
  948.         mov     edi, eax
  949.         push    esi
  950.         mov     ecx, [esi+DISK.NumPartitions]
  951.         mov     esi, [esi+DISK.Partitions]
  952.         rep movsd
  953.         pop     esi
  954. ; 3d. Set the field in the DISK structure to the new array.
  955.         xchg    [esi+DISK.Partitions], eax
  956. ; 3e. Free the old array.
  957.         call    free
  958. ; 4. Recognize the file system.
  959. ; 4a. Call the filesystem recognizer. It will allocate the PARTITION structure
  960. ; with possible filesystem-specific fields.
  961.         call    disk_detect_partition
  962. ; 4b. Check return value. If zero, return with list not changed; so far only
  963. ; the array was reallocated, this is ok for other code.
  964.         test    eax, eax
  965.         jz      .nothing
  966. ; 5. Insert the new partition to the list.
  967.         stosd
  968.         inc     [esi+DISK.NumPartitions]
  969. ; 6. Return.
  970. .nothing:
  971.         ret
  972. endp
  973.  
  974. ; This is an internal function called from disk_add_partition.
  975. ; It tries to recognize the file system on the partition and allocates the
  976. ; corresponding PARTITION structure with filesystem-specific fields.
  977. disk_detect_partition:
  978. ; This function inherits the stack frame from disk_add_partition. In stdcall
  979. ; with ebp-based frame arguments start from ebp+8, since [ebp]=saved ebp
  980. ; and [ebp+4]=return address.
  981. virtual at ebp+8
  982. .start  dq      ?
  983. .length dq      ?
  984. .disk   dd      ?
  985. end virtual
  986. ; 1. Read the bootsector to the buffer.
  987. ; When disk_add_partition is called, ebx contains a pointer to
  988. ; a three-sectors-sized buffer. This function saves ebx in the stack
  989. ; immediately before ebp.
  990.         mov     ebx, [ebp-4] ; get buffer
  991.         add     ebx, [esi+DISK.MediaInfo.SectorSize] ; advance over MBR data to bootsector data
  992.         add     ebp, 8       ; ebp points to part of PARTITION structure
  993.         xor     eax, eax     ; first sector of the partition
  994.         call    fs_read32_sys
  995.         push    eax
  996. ; 2. Run tests for all supported filesystems. If at least one test succeeded,
  997. ; go to 4.
  998. ; For tests:
  999. ; ebp -> first three fields of PARTITION structure, .start, .length, .disk;
  1000. ; [esp] = error code after bootsector read: 0 = ok, otherwise = failed,
  1001. ; ebx points to the buffer for bootsector,
  1002. ; ebx+[esi+DISK.MediaInfo.SectorSize] points to sector-sized buffer that can be used for anything.
  1003.         call    fat_create_partition
  1004.         test    eax, eax
  1005.         jnz     .success
  1006.         call    ntfs_create_partition
  1007.         test    eax, eax
  1008.         jnz     .success
  1009.         call    ext2_create_partition
  1010.         test    eax, eax
  1011.         jnz     .success
  1012.         call    xfs_create_partition
  1013.         test    eax, eax
  1014.         jnz     .success
  1015. ; 3. No file system has recognized the volume, so just allocate the PARTITION
  1016. ; structure without extra fields.
  1017.         movi    eax, sizeof.PARTITION
  1018.         call    malloc
  1019.         test    eax, eax
  1020.         jz      .nothing
  1021.         mov     edx, dword [ebp+PARTITION.FirstSector]
  1022.         mov     dword [eax+PARTITION.FirstSector], edx
  1023.         mov     edx, dword [ebp+PARTITION.FirstSector+4]
  1024.         mov     dword [eax+PARTITION.FirstSector+4], edx
  1025.         mov     edx, dword [ebp+PARTITION.Length]
  1026.         mov     dword [eax+PARTITION.Length], edx
  1027.         mov     edx, dword [ebp+PARTITION.Length+4]
  1028.         mov     dword [eax+PARTITION.Length+4], edx
  1029.         mov     [eax+PARTITION.Disk], esi
  1030.         mov     [eax+PARTITION.FSUserFunctions], default_fs_functions
  1031. .success:
  1032. .nothing:
  1033.         sub     ebp, 8 ; restore ebp
  1034. ; 4. Return with eax = pointer to PARTITION or NULL.
  1035.         pop     ecx
  1036.         ret
  1037.  
  1038. iglobal
  1039. align 4
  1040. default_fs_functions:
  1041.         dd      free
  1042.         dd      0       ; no user functions
  1043. endg
  1044.  
  1045. ; This function is called from file_system_lfn.
  1046. ; This handler gets the control each time when fn 70 is called
  1047. ; with unknown item of root subdirectory.
  1048. ; in: esi -> name
  1049. ;     ebp = 0 or rest of name relative to esi
  1050. ; out: if the handler processes path, it must not return in file_system_lfn,
  1051. ;      but instead pop return address and return directly to the caller
  1052. ;      otherwise simply return
  1053. dyndisk_handler:
  1054.         push    ebx edi         ; save registers used in file_system_lfn
  1055. ; 1. Acquire the mutex.
  1056.         mov     ecx, disk_list_mutex
  1057.         call    mutex_lock
  1058. ; 2. Loop over the list of DISK structures.
  1059. ; 2a. Initialize.
  1060.         mov     ebx, disk_list
  1061. .scan:
  1062. ; 2b. Get the next item.
  1063.         mov     ebx, [ebx+DISK.Next]
  1064. ; 2c. Check whether the list is done. If so, go to 3.
  1065.         cmp     ebx, disk_list
  1066.         jz      .notfound
  1067. ; 2d. Compare names. If names match, go to 5.
  1068.         mov     edi, [ebx+DISK.Name]
  1069.         push    esi
  1070. @@:
  1071. ; esi points to the name from fs operation; it is terminated by zero or slash.
  1072.         lodsb
  1073.         test    al, al
  1074.         jz      .eoin_dec
  1075.         cmp     al, '/'
  1076.         jz      .eoin
  1077. ; edi points to the disk name.
  1078.         inc     edi
  1079. ; edi points to lowercase name, this is a requirement for the driver.
  1080. ; Characters at esi can have any register. Lowercase the current character.
  1081. ; This lowercasing works for latin letters and digits; since the disk name
  1082. ; should not contain other symbols, this is ok.
  1083.         or      al, 20h
  1084.         cmp     al, [edi-1]
  1085.         jz      @b
  1086. .wrongname:
  1087. ; 2f. Names don't match. Continue the loop.
  1088.         pop     esi
  1089.         jmp     .scan
  1090. .notfound:
  1091. ; The loop is done and no name matches.
  1092. ; 3. Release the mutex.
  1093.         call    mutex_unlock
  1094. ; 4. Return normally.
  1095.         pop     edi ebx         ; restore registers used in file_system_lfn
  1096.         ret
  1097. ; part of 2d: the name matches partially, but we must check that this is full
  1098. ; equality.
  1099. .eoin_dec:
  1100.         dec     esi
  1101. .eoin:
  1102.         cmp     byte [edi], 0
  1103.         jnz     .wrongname
  1104. ; We found the addressed DISK structure.
  1105. ; 5. Reference the disk.
  1106.         lock inc [ebx+DISK.RefCount]
  1107. ; 6. Now we are sure that the DISK structure is not going to die at least
  1108. ; while we are working with it, so release the global mutex.
  1109.         call    mutex_unlock
  1110.         pop     ecx             ; pop from the stack saved value of esi
  1111. ; 7. Acquire the mutex for media object.
  1112.         pop     edi             ; restore edi
  1113.         lea     ecx, [ebx+DISK.MediaLock]
  1114.         call    mutex_lock
  1115. ; 8. Get the media object. If it is not NULL, reference it.
  1116.         xor     edx, edx
  1117.         cmp     [ebx+DISK.MediaInserted], dl
  1118.         jz      @f
  1119.         mov     edx, ebx
  1120.         inc     [ebx+DISK.MediaRefCount]
  1121. @@:
  1122. ; 9. Now we are sure that the media object, if it exists, is not going to die
  1123. ; at least while we are working with it, so release the mutex for media object.
  1124.         call    mutex_unlock
  1125.         mov     ecx, ebx
  1126.         pop     ebx eax         ; restore ebx, pop return address
  1127. ; 10. Check whether the fs operation wants to enumerate partitions (go to 11)
  1128. ; or work with some concrete partition (go to 12).
  1129.         cmp     byte [esi], 0
  1130.         jnz     .haspartition
  1131. ; 11. The fs operation wants to enumerate partitions.
  1132. ; 11a. Only "list directory" operation is applicable to /<diskname> path. Check
  1133. ; the operation code. If wrong, go to 13.
  1134.         cmp     dword [ebx], 1
  1135.         jnz     .access_denied
  1136. ; 11b. If the media is inserted, use 'fs_dyndisk_next' as an enumeration
  1137. ; procedure. Otherwise, use 'fs_dyndisk_next_nomedia'.
  1138.         mov     esi, fs_dyndisk_next_nomedia
  1139.         test    edx, edx
  1140.         jz      @f
  1141.         mov     esi, fs_dyndisk_next
  1142. @@:
  1143. ; 11c. Let the procedure from fs_lfn.inc do the job.
  1144.         jmp     file_system_lfn.maindir_noesi
  1145. .haspartition:
  1146. ; 12. The fs operation has specified some partition.
  1147. ; 12a. Store parameters for callback functions.
  1148.         push    edx
  1149.         push    ecx
  1150. ; 12b. Store callback functions.
  1151.         push    dyndisk_cleanup
  1152.         push    fs_dyndisk
  1153.         mov     edi, esp
  1154. ; 12c. Let the procedure from fs_lfn.inc do the job.
  1155.         jmp     file_system_lfn.found2
  1156. .access_denied:
  1157. ; 13. Fail the operation with the appropriate code.
  1158.         mov     dword [esp+32], ERROR_ACCESS_DENIED
  1159. .cleanup:
  1160. ; 14. Cleanup.
  1161.         mov     esi, ecx        ; disk*dereference assume that esi points to DISK
  1162. .cleanup_esi:
  1163.         test    edx, edx        ; if there are no media, we didn't reference it
  1164.         jz      @f
  1165.         call    disk_media_dereference
  1166. @@:
  1167.         call    disk_dereference
  1168. ; 15. Return.
  1169.         ret
  1170.  
  1171. ; This is a callback for cleaning up things called from file_system_lfn.found2.
  1172. dyndisk_cleanup:
  1173.         mov     esi, [edi+8]
  1174.         mov     edx, [edi+12]
  1175.         jmp     dyndisk_handler.cleanup_esi
  1176.  
  1177. ; This is a callback for enumerating partitions called from
  1178. ; file_system_lfn.maindir in the case of inserted media.
  1179. ; It just increments eax until DISK.NumPartitions reached and then
  1180. ; cleans up.
  1181. fs_dyndisk_next:
  1182.         cmp     eax, [ecx+DISK.NumPartitions]
  1183.         jae     .nomore
  1184.         inc     eax
  1185.         clc
  1186.         ret
  1187. .nomore:
  1188.         pusha
  1189.         mov     esi, ecx
  1190.         call    disk_media_dereference
  1191.         call    disk_dereference
  1192.         popa
  1193.         stc
  1194.         ret
  1195.  
  1196. ; This is a callback for enumerating partitions called from
  1197. ; file_system_lfn.maindir in the case of missing media.
  1198. ; In this case we create one pseudo-partition.
  1199. fs_dyndisk_next_nomedia:
  1200.         cmp     eax, 1
  1201.         jae     .nomore
  1202.         inc     eax
  1203.         clc
  1204.         ret
  1205. .nomore:
  1206.         pusha
  1207.         mov     esi, ecx
  1208.         call    disk_dereference
  1209.         popa
  1210.         stc
  1211.         ret
  1212.  
  1213. ; This is a callback for doing real work with selected partition.
  1214. ; Currently this is just placeholder, since no file systems are supported.
  1215. ; edi = esp -> {dd fs_dyndisk, dd dyndisk_cleanup, dd pointer to DISK, dd media object}
  1216. ; ecx = partition number, esi+ebp = ASCIIZ name
  1217. fs_dyndisk:
  1218.         dec     ecx     ; convert to zero-based partition index
  1219.         pop     edx edx edx ; edx = pointer to DISK, dword [esp] = NULL or edx
  1220. ; If the driver does not support insert notifications and we are the only fs
  1221. ; operation with this disk, ask the driver whether the media
  1222. ; was inserted/removed/changed. Otherwise, assume that media status is valid.
  1223.         test    byte [edx+DISK.DriverFlags], DISK_NO_INSERT_NOTIFICATION
  1224.         jz      .media_accurate
  1225.         push    ecx esi
  1226.         mov     esi, edx
  1227.         cmp     dword [esp+8], 0
  1228.         jz      .test_no_media
  1229.         cmp     [esi+DISK.MediaRefCount], 2
  1230.         jnz     .media_accurate_pop
  1231.         lea     edx, [esi+DISK.MediaInfo]
  1232.         and     [edx+DISKMEDIAINFO.Flags], 0
  1233.         mov     al, DISKFUNC.querymedia
  1234.         stdcall disk_call_driver, edx
  1235.         test    eax, eax
  1236.         jz      .media_accurate_pop
  1237.         stdcall disk_media_dereference  ; drop our reference so that disk_media_changed could close the media
  1238.         stdcall disk_media_changed, esi, 0
  1239.         and     dword [esp+8], 0        ; no media
  1240. .test_no_media:
  1241.         stdcall disk_media_changed, esi, 1      ; issue fake notification
  1242.                 ; if querymedia() inside disk_media_changed returns error, the notification is ignored
  1243.         cmp     [esi+DISK.MediaInserted], 0
  1244.         jz      .media_accurate_pop
  1245.         lock inc [esi+DISK.MediaRefCount]
  1246.         mov     dword [esp+8], esi
  1247. .media_accurate_pop:
  1248.         mov     edx, esi
  1249.         pop     esi ecx
  1250. .media_accurate:
  1251.         pop     eax
  1252.         test    eax, eax
  1253.         jz      .nomedia
  1254. .main:
  1255.         cmp     ecx, [edx+DISK.NumPartitions]
  1256.         jae     .notfound
  1257.         mov     eax, [edx+DISK.Partitions]
  1258.         mov     eax, [eax+ecx*4]
  1259.         mov     edi, [eax+PARTITION.FSUserFunctions]
  1260.         mov     ecx, [ebx]
  1261.         cmp     [edi+4], ecx
  1262.         jbe     .unsupported
  1263.         push    edx
  1264.         push    ebp
  1265.         mov     ebp, eax
  1266.         call    dword [edi+8+ecx*4]
  1267.         pop     ebp
  1268.         pop     edx
  1269.         mov     dword [esp+32], eax
  1270.         mov     dword [esp+20], ebx
  1271. .cleanup:
  1272.         mov     esi, edx
  1273.         call    disk_media_dereference
  1274.         call    disk_dereference
  1275.         ret
  1276. .nofs:
  1277.         mov     dword [esp+32], ERROR_UNKNOWN_FS
  1278.         jmp     .cleanup
  1279. .notfound:
  1280.         mov     dword [esp+32], ERROR_FILE_NOT_FOUND
  1281.         jmp     .cleanup
  1282. .unsupported:
  1283.         cmp     edi, default_fs_functions
  1284.         jz      .nofs
  1285.         mov     dword [esp+32], ERROR_UNSUPPORTED_FS
  1286.         jmp     .cleanup
  1287. .nomedia:
  1288.         test    ecx, ecx
  1289.         jnz     .notfound
  1290.         mov     dword [esp+32], ERROR_DEVICE
  1291.         mov     esi, edx
  1292.         call    disk_dereference
  1293.         ret
  1294.  
  1295. ; This function is called from file_system_lfn.
  1296. ; This handler is called when virtual root is enumerated
  1297. ; and must return all items which can be handled by this.
  1298. ; It is called several times, first time with eax=0
  1299. ; in: eax = 0 for first call, previously returned value for subsequent calls
  1300. ; out: eax = 0 => no more items
  1301. ;      eax != 0 => buffer pointed to by edi contains name of item
  1302. dyndisk_enum_root:
  1303.         push    edx             ; save register used in file_system_lfn
  1304.         mov     ecx, disk_list_mutex    ; it will be useful
  1305. ; 1. If this is the first call, acquire the mutex and initialize.
  1306.         test    eax, eax
  1307.         jnz     .notfirst
  1308.         call    mutex_lock
  1309.         mov     eax, disk_list
  1310. .notfirst:
  1311. ; 2. Get next item.
  1312.         mov     eax, [eax+DISK.Next]
  1313. ; 3. If there are no more items, go to 6.
  1314.         cmp     eax, disk_list
  1315.         jz      .last
  1316. ; 4. Copy name from the DISK structure to edi.
  1317.         push    eax esi
  1318.         mov     esi, [eax+DISK.Name]
  1319. @@:
  1320.         lodsb
  1321.         stosb
  1322.         test    al, al
  1323.         jnz     @b
  1324.         pop     esi eax
  1325. ; 5. Return with eax = item.
  1326.         pop     edx             ; restore register used in file_system_lfn
  1327.         ret
  1328. .last:
  1329. ; 6. Release the mutex and return with eax = 0.
  1330.         call    mutex_unlock
  1331.         xor     eax, eax
  1332.         pop     edx             ; restore register used in file_system_lfn
  1333.         ret
  1334.