;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; ;; ;; Copyright (C) KolibriOS team 2011-2012. All rights reserved. ;; ;; Distributed under terms of the GNU General Public License ;; ;; ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; $Revision$ ; ============================================================================= ; ================================= Constants ================================= ; ============================================================================= ; Error codes for callback functions. DISK_STATUS_OK = 0 ; success DISK_STATUS_GENERAL_ERROR = -1; if no other code is suitable DISK_STATUS_INVALID_CALL = 1 ; invalid input parameters DISK_STATUS_NO_MEDIA = 2 ; no media present DISK_STATUS_END_OF_MEDIA = 3 ; end of media while reading/writing data ; Driver flags. Represent bits in DISK.DriverFlags. DISK_NO_INSERT_NOTIFICATION = 1 ; Media flags. Represent bits in DISKMEDIAINFO.Flags. DISK_MEDIA_READONLY = 1 ; If too many partitions are detected,there is probably an error on the disk. ; 256 partitions should be enough for any reasonable use. ; Also, the same number is limiting the number of MBRs to process; if ; too many MBRs are visible,there probably is a loop in the MBR structure. MAX_NUM_PARTITIONS = 256 ; ============================================================================= ; ================================ Structures ================================= ; ============================================================================= ; This structure defines all callback functions for working with the physical ; device. They are implemented by a driver. Objects with this structure reside ; in a driver. struct DISKFUNC strucsize dd ? ; Size of the structure. This field is intended for possible extensions of ; this structure. If a new function is added to this structure and a driver ; implements an old version, the caller can detect this by checking .strucsize, ; so the driver remains compatible. close dd ? ; The pointer to the function which frees all driver-specific resources for ; the disk. ; Optional, may be NULL. ; void close(void* userdata); closemedia dd ? ; The pointer to the function which informs the driver that the kernel has ; finished all processing with the current media. If media is removed, the ; driver should decline all requests to that media with DISK_STATUS_NO_MEDIA, ; even if new media is inserted, until this function is called. If media is ; removed, a new call to 'disk_media_changed' is not allowed until this ; function is called. ; Optional, may be NULL (if media is not removable). ; void closemedia(void* userdata); querymedia dd ? ; The pointer to the function which determines capabilities of the media. ; int querymedia(void* userdata, DISKMEDIAINFO* info); ; Return value: one of DISK_STATUS_* read dd ? ; The pointer to the function which reads data from the device. ; int read(void* userdata, void* buffer, __int64 startsector, int* numsectors); ; input: *numsectors = number of sectors to read ; output: *numsectors = number of sectors which were successfully read ; Return value: one of DISK_STATUS_* write dd ? ; The pointer to the function which writes data to the device. ; Optional, may be NULL. ; int write(void* userdata, void* buffer, __int64 startsector, int* numsectors); ; input: *numsectors = number of sectors to write ; output: *numsectors = number of sectors which were successfully written ; Return value: one of DISK_STATUS_* flush dd ? ; The pointer to the function which flushes the internal device cache. ; Optional, may be NULL. ; int flush(void* userdata); ; Return value: one of DISK_STATUS_* ; Note that read/write are called by the cache manager, so a driver should not ; create a software cache. This function is implemented for flushing a hardware ; cache, if it exists. adjust_cache_size dd ? ; The pointer to the function which returns the cache size for this device. ; Optional, may be NULL. ; unsigned int adjust_cache_size(unsigned int suggested_size); ; Return value: 0 = disable cache, otherwise = used cache size in bytes. ends ; This structure holds information on a medium. ; Objects with this structure are allocated by the kernel as a part of the DISK ; structure and are filled by a driver in the 'querymedia' callback. struct DISKMEDIAINFO Flags dd ? ; Combination of DISK_MEDIA_* bits. SectorSize dd ? ; Size of the sector. Capacity dq ? ; Size of the media in sectors. ends ; This structure represents the disk cache. To follow the old implementation, ; there are two distinct caches for a disk, one for "system" data,and the other ; for "application" data. struct DISKCACHE mutex MUTEX ; Lock to protect the cache. ; The following fields are inherited from data32.inc:cache_ideX. pointer dd ? data_size dd ? ; unused data dd ? sad_size dd ? search_start dd ? ends ; This structure represents a disk device and its media for the kernel. ; This structure is allocated by the kernel in the 'disk_add' function, ; freed in the 'disk_dereference' function. struct DISK ; Fields of disk object Next dd ? Prev dd ? ; All disk devices are linked in one list with these two fields. ; Head of the list is the 'disk_list' variable. Functions dd ? ; Pointer to the 'DISKFUNC' structure with driver functions. Name dd ? ; Pointer to the string used for accesses through the global filesystem. UserData dd ? ; This field is passed to all callback functions so a driver can decide which ; physical device is addressed. DriverFlags dd ? ; Bitfield. Currently only DISK_NO_INSERT_NOTIFICATION bit is defined. ; If it is set, the driver will never issue 'disk_media_changed' notification ; with argument set to true, so the kernel must try to detect media during ; requests from the file system. RefCount dd ? ; Count of active references to this structure. One reference is kept during ; the lifetime of the structure between 'disk_add' and 'disk_del'. ; Another reference is taken during any filesystem operation for this disk. ; One reference is added if media is inserted. ; The structure is destroyed when the reference count decrements to zero: ; this usually occurs in 'disk_del', but can be delayed to the end of last ; filesystem operation, if one is active. MediaLock MUTEX ; Lock to protect the MEDIA structure. See the description after ; 'disk_list_mutex' for the locking strategy. ; Fields of media object MediaInserted db ? ; 0 if media is not inserted, nonzero otherwise. MediaUsed db ? ; 0 if media fields are not used, nonzero otherwise. If .MediaRefCount is ; nonzero, this field is nonzero too; however, when .MediaRefCount goes ; to zero, there is some time interval during which media object is still used. align 4 ; The following fields are not valid unless either .MediaInserted is nonzero ; or they are accessed from a code which has obtained the reference when ; .MediaInserted was nonzero. MediaRefCount dd ? ; Count of active references to the media object. One reference is kept during ; the lifetime of the media between two calls to 'disk_media_changed'. ; Another reference is taken during any filesystem operation for this media. ; The callback 'closemedia' is called when the reference count decrements to ; zero: this usually occurs in 'disk_media_changed', but can be delayed to the ; end of the last filesystem operation, if one is active. MediaInfo DISKMEDIAINFO ; This field keeps information on the current media. NumPartitions dd ? ; Number of partitions on this media. Partitions dd ? ; Pointer to array of .NumPartitions pointers to PARTITION structures. cache_size dd ? ; inherited from cache_ideX_size SysCache DISKCACHE AppCache DISKCACHE ; Two caches for the disk. ends ; This structure represents one partition for the kernel. This is a base ; template, the actual contents after common fields is determined by the ; file system code for this partition. struct PARTITION FirstSector dq ? ; First sector of the partition. Length dq ? ; Length of the partition in sectors. Disk dd ? ; Pointer to parent DISK structure. FSUserFunctions dd ? ; Handlers for the sysfunction 70h. This field is a pointer to the following ; array. The first dword is a number of supported subfunctions, other dwords ; point to handlers of corresponding subfunctions. ; This field is 0 if file system is not recognized. ; ...fs-specific data may follow... ends ; This is an external structure, it represents an entry in the partition table. struct PARTITION_TABLE_ENTRY Bootable db ? ; 80h = bootable partition, 0 = non-bootable partition, other values = invalid FirstHead db ? FirstSector db ? FirstTrack db ? ; Coordinates of first sector in CHS. Type db ? ; Partition type, one of predefined constants. 0 = empty, several types denote ; extended partition (see process_partition_table_entry), we are not interested ; in other values. LastHead db ? LastSector db ? LastTrack db ? ; Coordinates of last sector in CHS. FirstAbsSector dd ? ; Coordinate of first sector in LBA. Length dd ? ; Length of the partition in sectors. ends ; ============================================================================= ; ================================ Global data ================================ ; ============================================================================= iglobal ; The pseudo-item for the list of all DISK structures. ; Initialized to the empty list. disk_list: dd disk_list dd disk_list endg uglobal ; This mutex guards all operations with the global list of DISK structures. disk_list_mutex MUTEX ; * There are two dependent objects, a disk and a media. In the simplest case, ; disk and media are both non-removable. However, in the general case both ; can be removed at any time, simultaneously or only media,and this makes things ; complicated. ; * For efficiency, both disk and media objects are located in the one ; structure named DISK. However, logically they are different. ; * The following operations use data of disk object: adding (disk_add); ; deleting (disk_del); filesystem (fs_lfn which eventually calls ; dyndisk_handler or dyndisk_enum_root). ; * The following operations use data of media object: adding/removing ; (disk_media_changed); filesystem (fs_lfn which eventually calls ; dyndisk_handler; dyndisk_enum_root doesn't work with media). ; * Notifications disk_add, disk_media_changed, disk_del are synchronized ; between themselves, this is a requirement for the driver. However, file ; system operations are asynchronous, can be issued at any time by any ; thread. ; * We must prevent a situation when a filesystem operation thinks that the ; object is still valid but in fact the notification has destroyed the ; object. So we keep a reference counter for both disk and media and destroy ; the object when this counter goes to zero. ; * The driver must know when it is safe to free driver-allocated resources. ; The object can be alive even after death notification has completed. ; We use special callbacks to satisfy both assertions: 'close' for the disk ; and 'closemedia' for the media. The destruction of the object includes ; calling the corresponding callback. ; * Each filesystem operation keeps one reference for the disk and one ; reference for the media. Notification disk_del forces notification on the ; media death, so the reference counter for the disk is always not less than ; the reference counter for the media. ; * Two operations "get the object" and "increment the reference counter" can ; not be done simultaneously. We use a mutex to guard the consistency here. ; It must be a part of the container for the object, so that this mutex can ; be acquired as a part of getting the object from the container. The ; container for disk object is the global list, and this list is guarded by ; 'disk_list_mutex'. The container for media object is the disk object, and ; the corresponding mutex is DISK.MediaLock. ; * Notifications do not change the data of objects, they can only remove ; objects. Thus we don't need another synchronization at this level. If two ; filesystem operations are referencing the same filesystem data, this is ; better resolved at the level of the filesystem. endg iglobal ; The function 'disk_scan_partitions' needs three 512-byte buffers for ; MBR, bootsector and fs-temporary sector data. It can not use the static ; buffers always, since it can be called for two or more disks in parallel. ; However, this case is not typical. We reserve three static 512-byte buffers ; and a flag that these buffers are currently used. If 'disk_scan_partitions' ; detects that the buffers are currently used, it allocates buffers from the ; heap. ; The flag is implemented as a global dword variable. When the static buffers ; are not used, the value is -1. When the static buffers are used, the value ; is normally 0 and temporarily can become greater. The function increments ; this value. If the resulting value is zero, it uses the buffers and ; decrements the value when the job is done. Otherwise, it immediately ; decrements the value and uses buffers from the heap, allocated in the ; beginning and freed in the end. partition_buffer_users dd -1 endg uglobal ; The static buffers for MBR, bootsector and fs-temporary sector data. align 16 mbr_buffer rb 512 bootsect_buffer rb 512 fs_tmp_buffer rb 512 endg iglobal ; This is the array of default implementations of driver callbacks. ; Same as DRIVERFUNC structure except for the first field; all functions must ; have the default implementations. align 4 disk_default_callbacks: dd disk_default_close dd disk_default_closemedia dd disk_default_querymedia dd disk_default_read dd disk_default_write dd disk_default_flush dd disk_default_adjust_cache_size endg ; ============================================================================= ; ================================= Functions ================================= ; ============================================================================= ; This function registers a disk device. ; This includes: ; - allocating an internal structure describing this device; ; - registering this structure in the global filesystem. ; The function initializes the disk as if there is no media. If a media is ; present, the function 'disk_media_changed' should be called after this ; function succeeds. ; Parameters: ; [esp+4] = pointer to DISKFUNC structure with the callbacks ; [esp+8] = pointer to name (ASCIIZ string) ; [esp+12] = userdata to be passed to the callbacks as is. ; [esp+16] = flags, bitfield. Currently only DISK_NO_INSERT_NOTIFICATION bit ; is defined. ; Return value: ; NULL = operation has failed ; non-NULL = handle of the disk. This handle can be used ; in the operations with other Disk* functions. ; The handle is the pointer to the internal structure DISK. disk_add: push ebx esi ; save used registers to be stdcall ; 1. Allocate the DISK structure. ; 1a. Call the heap manager. push sizeof.DISK pop eax call malloc ; 1b. Check the result. If allocation failed, return (go to 9) with eax = 0. test eax, eax jz .nothing ; 2. Copy the disk name to the DISK structure. ; 2a. Get length of the name, including the terminating zero. mov ebx, [esp+8+8] ; ebx = pointer to name push eax ; save allocated pointer to DISK xor eax, eax ; the argument of malloc() is in eax @@: inc eax cmp byte [ebx+eax-1], 0 jnz @b ; 2b. Call the heap manager. Note that it can change ebx. push ebx call malloc pop ebx ; 2c. Check the result. If allocation failed, go to 7. pop esi ; restore allocated pointer to DISK test eax, eax jz .free ; 2d. Store the allocated pointer to the DISK structure. mov [esi+DISK.Name], eax ; 2e. Copy the name. @@: mov dl, [ebx] mov [eax], dl inc ebx inc eax test dl, dl jnz @b ; 3. Copy other arguments of the function to the DISK structure. mov eax, [esp+4+8] mov [esi+DISK.Functions], eax mov eax, [esp+12+8] mov [esi+DISK.UserData], eax mov eax, [esp+16+8] mov [esi+DISK.DriverFlags], eax ; 4. Initialize other fields of the DISK structure. ; Media is not inserted, reference counter is 1. lea ecx, [esi+DISK.MediaLock] call mutex_init xor eax, eax mov dword [esi+DISK.MediaInserted], eax inc eax mov [esi+DISK.RefCount], eax ; The DISK structure is initialized. ; 5. Insert the new structure to the global list. ; 5a. Acquire the mutex. mov ecx, disk_list_mutex call mutex_lock ; 5b. Insert item to the tail of double-linked list. mov edx, disk_list list_add_tail esi, edx ;esi= new edx= list head ; 5c. Release the mutex. call mutex_unlock ; 6. Return with eax = pointer to DISK. xchg eax, esi jmp .nothing .free: ; Memory allocation for DISK structure succeeded, but for disk name failed. ; 7. Free the DISK structure. xchg eax, esi call free ; 8. Return with eax = 0. xor eax, eax .nothing: ; 9. Return. pop esi ebx ; restore used registers to be stdcall ret 16 ; purge 4 dword arguments to be stdcall ; This function deletes a disk device from the global filesystem. ; This includes: ; - removing a media including all partitions; ; - deleting this structure from the global filesystem; ; - dereferencing the DISK structure and possibly destroying it. ; Parameters: ; [esp+4] = handle of the disk, i.e. the pointer to the DISK structure. ; Return value: none. disk_del: push esi ; save used registers to be stdcall ; 1. Force media to be removed. If the media is already removed, the ; call does nothing. mov esi, [esp+4+4] ; esi = handle of the disk stdcall disk_media_changed, esi, 0 ; 2. Delete the structure from the global list. ; 2a. Acquire the mutex. mov ecx, disk_list_mutex call mutex_lock ; 2b. Delete item from double-linked list. mov eax, [esi+DISK.Next] mov edx, [esi+DISK.Prev] mov [eax+DISK.Prev], edx mov [edx+DISK.Next], eax ; 2c. Release the mutex. call mutex_unlock ; 3. The structure still has one reference created in disk_add. Remove this ; reference. If there are no other references, disk_dereference will free the ; structure. call disk_dereference ; 4. Return. pop esi ; restore used registers to be stdcall ret 4 ; purge 1 dword argument to be stdcall ; This is an internal function which removes a previously obtained reference ; to the disk. If this is the last reference, this function lets the driver ; finalize all associated data, and afterwards frees the DISK structure. ; esi = pointer to DISK structure disk_dereference: ; 1. Decrement reference counter. Use atomic operation to correctly handle ; possible simultaneous calls. lock dec [esi+DISK.RefCount] ; 2. If the result is nonzero, there are other references, so nothing to do. ; In this case, return (go to 4). jnz .nothing ; 3. If we are here, we just removed the last reference and must destroy the ; disk object. ; 3a. Call the driver. mov al, DISKFUNC.close stdcall disk_call_driver ; 3b. Free the structure. xchg eax, esi call free ; 4. Return. .nothing: ret ; This is an internal function which removes a previously obtained reference ; to the media. If this is the last reference, this function calls 'closemedia' ; callback to signal the driver that the processing has finished and it is safe ; to inform about a new media. ; esi = pointer to DISK structure disk_media_dereference: ; 1. Decrement reference counter. Use atomic operation to correctly handle ; possible simultaneous calls. lock dec [esi+DISK.MediaRefCount] ; 2. If the result is nonzero, there are other references, so nothing to do. ; In this case, return (go to 4). jnz .nothing ; 3. If we are here, we just removed the last reference and must destroy the ; media object. ; Note that the same place inside the DISK structure is reused for all media ; objects, so we must guarantee that reusing does not happen while freeing. ; Reusing is only possible when someone processes a new media. There are two ; mutually exclusive variants: ; * driver issues media insert notifications (DISK_NO_INSERT_NOTIFICATION bit ; in DISK.DriverFlags is not set). In this case, we require from the driver ; that such notification (except for the first one) can occur only after a ; call to 'closemedia' callback. ; * driver does not issue media insert notifications. In this case, the kernel ; itself must sometimes check whether media is inserted. We have the flag ; DISK.MediaUsed, visible to the kernel. This flag signals to the other parts ; of kernel that the way is free. ; In the first case other parts of the kernel do not use DISK.MediaUsed, so it ; does not matter when this flag is cleared. In the second case this flag must ; be cleared after all other actions, including call to 'closemedia'. ; 3a. Free all partitions. push esi edi mov edi, [esi+DISK.NumPartitions] mov esi, [esi+DISK.Partitions] test edi, edi jz .nofree .freeloop: lodsd call free dec edi jnz .freeloop .nofree: pop edi esi ; 3b. Free the cache. call disk_free_cache ; 3c. Call the driver. mov al, DISKFUNC.closemedia stdcall disk_call_driver ; 3d. Clear the flag. mov [esi+DISK.MediaUsed], 0 .nothing: ret ; This function is called by the driver and informs the kernel that the media ; has changed. If the media is non-removable, it is called exactly once ; immediately after 'disk_add' and once from 'disk_del'. ; Parameters: ; [esp+4] = handle of the disk, i.e. the pointer to the DISK structure. ; [esp+8] = new status of the media: zero = no media, nonzero = media inserted. disk_media_changed: push ebx esi edi ; save used registers to be stdcall ; 1. Remove the existing media, if it is present. mov esi, [esp+4+12] ; esi = pointer to DISK ; 1a. Check whether it is present. Since DISK.MediaInserted is changed only ; in this function and calls to this function are synchronized, no lock is ; required for checking. cmp [esi+DISK.MediaInserted], 0 jz .noremove ; We really need to remove the media. ; 1b. Acquire mutex. lea ecx, [esi+DISK.MediaLock] call mutex_lock ; 1c. Clear the flag. mov [esi+DISK.MediaInserted], 0 ; 1d. Release mutex. call mutex_unlock ; 1e. Remove the "lifetime" reference and possibly destroy the structure. call disk_media_dereference .noremove: ; 2. Test whether there is new media. cmp dword [esp+8+12], 0 jz .noinsert ; Yep, there is. ; 3. Process the new media. We assume that all media fields are available to ; use, see comments in 'disk_media_dereference' (this covers using by previous ; media referencers) and note that calls to this function are synchronized ; (this covers using by new media referencers). ; 3a. Call the 'querymedia' callback. ; .Flags are set to zero for possible future extensions. lea edx, [esi+DISK.MediaInfo] and [edx+DISKMEDIAINFO.Flags], 0 mov al, DISKFUNC.querymedia stdcall disk_call_driver, edx ; 3b. Check the result of the callback. Abort if it failed. test eax, eax jnz .noinsert ; 3c. Allocate the cache unless disabled by the driver. Abort if failed. call disk_init_cache test al, al jz .noinsert ; 3d. Acquire the lifetime reference for the media object. inc [esi+DISK.MediaRefCount] ; 3e. Scan for partitions. Ignore result; the list of partitions is valid even ; on errors. call disk_scan_partitions ; 3f. Media is inserted and available for use. inc [esi+DISK.MediaInserted] .noinsert: ; 4. Return. pop edi esi ebx ; restore used registers to be stdcall ret 8 ; purge 2 dword arguments to be stdcall ; This function is a thunk for all functions of a disk driver. ; It checks whether the referenced function is implemented in the driver. ; If so, this function jumps to the function in the driver. ; Otherwise, it jumps to the default implementation. ; al = offset of function in the DISKFUNC structure; ; esi = pointer to the DISK structure; ; stack is the same as for the corresponding function except that the ; first parameter (void* userdata) is prepended automatically. disk_call_driver: movzx eax, al ; eax = offset of function in the DISKFUNC structure ; 1. Prepend the first argument to the stack. pop ecx ; ecx = return address push [esi+DISK.UserData] ; add argument push ecx ; save return address ; 2. Check that the required function is inside the table. If not, go to 5. mov ecx, [esi+DISK.Functions] cmp eax, [ecx+DISKFUNC.strucsize] jae .default ; 3. Check that the required function is implemented. If not, go to 5. mov ecx, [ecx+eax] test ecx, ecx jz .default ; 4. Jump to the required function. jmp ecx .default: ; 5. Driver does not implement the required function; use default implementation. jmp dword [disk_default_callbacks+eax-4] ; The default implementation of DISKFUNC.querymedia. disk_default_querymedia: push DISK_STATUS_INVALID_CALL pop eax ret 8 ; The default implementation of DISKFUNC.read and DISKFUNC.write. disk_default_read: disk_default_write: push DISK_STATUS_INVALID_CALL pop eax ret 20 ; The default implementation of DISKFUNC.close, DISKFUNC.closemedia and ; DISKFUNC.flush. disk_default_close: disk_default_closemedia: disk_default_flush: xor eax, eax ret 4 ; The default implementation of DISKFUNC.adjust_cache_size. disk_default_adjust_cache_size: mov eax, [esp+4] ret 4 ; This is an internal function called from 'disk_media_changed' when a new media ; is detected. It creates the list of partitions for the media. ; If media is not partitioned, then the list consists of one partition which ; covers all the media. ; esi = pointer to the DISK structure. disk_scan_partitions: ; 1. Initialize .NumPartitions and .Partitions fields as zeros: empty list. and [esi+DISK.NumPartitions], 0 and [esi+DISK.Partitions], 0 ; 2. Currently we can work only with 512-bytes sectors. Check this restriction. ; The only exception is 2048-bytes CD/DVD, but they are not supported yet by ; this code. cmp [esi+DISK.MediaInfo.SectorSize], 512 jz .doscan DEBUGF 1,'K : sector size is %d, only 512 is supported\n',[esi+DISK.MediaInfo.SectorSize] ret .doscan: ; 3. Acquire the buffer for MBR and bootsector tests. See the comment before ; the 'partition_buffer_users' variable. mov ebx, mbr_buffer ; assume the global buffer is free lock inc [partition_buffer_users] jz .buffer_acquired ; yes, it is free lock dec [partition_buffer_users] ; no, we must allocate stdcall kernel_alloc, 512*3 test eax, eax jz .nothing xchg eax, ebx .buffer_acquired: ; MBR/EBRs are organized in the chain. We use a loop over MBR/EBRs, but no ; more than MAX_NUM_PARTITION times. ; 4. Prepare things for the loop. ; ebp will hold the sector number for current MBR/EBR. ; [esp] will hold the sector number for current extended partition, if there ; is one. ; [esp+4] will hold the counter that prevents long loops. push ebp ; save ebp push MAX_NUM_PARTITIONS ; the counter of max MBRs to process xor ebp, ebp ; start from sector zero push ebp ; no extended partition yet .new_mbr: ; 5. Read the current sector. ; Note that 'read' callback operates with 64-bit sector numbers, so we must ; push additional zero as a high dword of sector number. mov al, DISKFUNC.read push 1 stdcall disk_call_driver, ebx, ebp, 0, esp pop ecx ; 6. If the read has failed, abort the loop. dec ecx jnz .mbr_failed ; 7. Check the MBR/EBR signature. If it is wrong, abort the loop. ; Soon we will access the partition table which starts at ebx+0x1BE, ; so we can fill its address right now. If we do it now, then the addressing ; [ecx+0x40] is shorter than [ebx+0x1fe]: one-byte offset vs 4-bytes offset. lea ecx, [ebx+0x1be] ; ecx -> partition table cmp word [ecx+0x40], 0xaa55 jnz .mbr_failed ; 8. The MBR is treated differently from EBRs. For MBR we additionally need to ; execute step 9 and possibly step 10. test ebp, ebp jnz .mbr ; The partition table can be present or not present. In the first case, we just ; read the MBR. In the second case, we just read the bootsector for a ; filesystem. ; The following algorithm is used to distinguish between these cases. ; A. If at least one entry of the partition table is invalid, this is ; a bootsector. See the description of 'is_partition_table_entry' for ; definition of validity. ; B. If all entries are empty (filesystem type field is zero) and the first ; byte is jmp opcode (0EBh or 0E9h), this is a bootsector which happens to ; have zeros in the place of partition table. ; C. Otherwise, this is an MBR. ; 9. Test for MBR vs bootsector. ; 9a. Check entries. If any is invalid, go to 10 (rule A). call is_partition_table_entry jc .notmbr add ecx, 10h call is_partition_table_entry jc .notmbr add ecx, 10h call is_partition_table_entry jc .notmbr add ecx, 10h call is_partition_table_entry jc .notmbr ; 9b. Check types of the entries. If at least one is nonzero, go to 11 (rule C). mov al, [ecx-30h+PARTITION_TABLE_ENTRY.Type] or al, [ecx-20h+PARTITION_TABLE_ENTRY.Type] or al, [ecx-10h+PARTITION_TABLE_ENTRY.Type] or al, [ecx+PARTITION_TABLE_ENTRY.Type] jnz .mbr ; 9c. Empty partition table or bootsector with many zeroes? (rule B) cmp byte [ebx], 0EBh jz .notmbr cmp byte [ebx], 0E9h jnz .mbr .notmbr: ; 10. This is not an MBR. The media is not partitioned. Create one partition ; which covers all the media and abort the loop. stdcall disk_add_partition, 0, 0, \ dword [esi+DISK.MediaInfo.Capacity], dword [esi+DISK.MediaInfo.Capacity+4] jmp .done .mbr: ; 11. Process all entries of the new MBR/EBR lea ecx, [ebx+0x1be] ; ecx -> partition table push 0 ; assume no extended partition call process_partition_table_entry add ecx, 10h call process_partition_table_entry add ecx, 10h call process_partition_table_entry add ecx, 10h call process_partition_table_entry pop ebp ; 12. Test whether we found a new EBR and should continue the loop. ; 12a. If there was no next EBR, return. test ebp, ebp jz .done ; Ok, we have EBR. ; 12b. EBRs addresses are relative to the start of extended partition. ; For simplicity, just abort if an 32-bit overflow occurs; large disks ; are most likely partitioned with GPT, not MBR scheme, since the precise ; calculation here would increase limit just twice at the price of big ; compatibility problems. pop eax ; load extended partition add ebp, eax jc .mbr_failed ; 12c. If extended partition has not yet started, start it. test eax, eax jnz @f mov eax, ebp @@: ; 12c. If the limit is not exceeded, continue the loop. dec dword [esp] push eax ; store extended partition jnz .new_mbr .mbr_failed: .done: ; 13. Cleanup after the loop. pop eax ; not important anymore pop eax ; not important anymore pop ebp ; restore ebp ; 14. Release the buffer. ; 14a. Test whether it is the global buffer or we have allocated it. cmp ebx, mbr_buffer jz .release_partition_buffer ; 14b. If we have allocated it, free it. xchg eax, ebx call free jmp .nothing ; 14c. Otherwise, release reference. .release_partition_buffer: lock dec [partition_buffer_users] .nothing: ; 15. Return. ret ; This is an internal function called from disk_scan_partitions. It checks ; whether the entry pointed to by ecx is a valid entry of partition table. ; The entry is valid if the first byte is 0 or 80h, the first sector plus the ; length is less than twice the size of media. Multiplication by two is ; required since the size mentioned in the partition table can be slightly ; greater than the real size. is_partition_table_entry: ; 1. Check .Bootable field. mov al, [ecx+PARTITION_TABLE_ENTRY.Bootable] and al, 7Fh jnz .invalid ; 3. Calculate first sector + length. Note that .FirstAbsSector is relative ; to the MBR/EBR, so the real sum is ebp + .FirstAbsSector + .Length. mov eax, ebp xor edx, edx add eax, [ecx+PARTITION_TABLE_ENTRY.FirstAbsSector] adc edx, 0 add eax, [ecx+PARTITION_TABLE_ENTRY.Length] adc edx, 0 ; 4. Divide by two. shr edx, 1 rcr eax, 1 ; 5. Compare with capacity. If the subtraction (edx:eax) - .Capacity does not ; overflow, this is bad. sub eax, dword [esi+DISK.MediaInfo.Capacity] sbb edx, dword [esi+DISK.MediaInfo.Capacity+4] jnc .invalid .valid: ; 5. Return success: CF is cleared. clc ret .invalid: ; 6. Return fail: CF is set. stc ret ; This is an internal function called from disk_scan_partitions. It processes ; the entry pointed to by ecx. ; * If the entry is invalid, just ignore this entry. ; * If the type is zero, just ignore this entry. ; * If the type is one of types for extended partition, store the address ; of this partition as the new MBR in [esp+4]. ; * Otherwise, add the partition to the list of partitions for this disk. ; We don't use the type from the entry to identify the file system; ; fs-specific checks do this more reliably. process_partition_table_entry: ; 1. Check for valid entry. If invalid, return (go to 5). call is_partition_table_entry jc .nothing ; 2. Check for empty entry. If invalid, return (go to 5). mov al, [ecx+PARTITION_TABLE_ENTRY.Type] test al, al jz .nothing ; 3. Check for extended partition. If extended, go to 6. irp type,\ 0x05,\ ; DOS: extended partition 0x0f,\ ; WIN95: extended partition, LBA-mapped 0xc5,\ ; DRDOS/secured: extended partition 0xd5 ; Old Multiuser DOS secured: extended partition { cmp al, type jz .extended } ; 4. If we are here, that is a normal partition. Add it to the list. ; Note that the first sector is relative to MBR/EBR. mov eax, ebp xor edx, edx add eax, [ecx+PARTITION_TABLE_ENTRY.FirstAbsSector] adc edx, 0 push ecx stdcall disk_add_partition, eax, edx, \ [ecx+PARTITION_TABLE_ENTRY.Length], 0 pop ecx .nothing: ; 5. Return. ret .extended: ; 6. If we are here, that is an extended partition. Store the address. mov eax, [ecx+PARTITION_TABLE_ENTRY.FirstAbsSector] mov [esp+4], eax ret ; This is an internal function called from disk_scan_partitions and ; process_partition_table_entry. It adds one partition to the list of ; partitions for the media. proc disk_add_partition stdcall uses ebx edi, start:qword, length:qword ; 1. Check that this partition will not exceed the limit on total number. cmp [esi+DISK.NumPartitions], MAX_NUM_PARTITIONS jae .nothing ; 2. Check that this partition does not overlap with any already registered ; partition. Since any file system assumes that the disk data will not change ; outside of its control, such overlap could be destructive. ; Since the number of partitions is usually very small and is guaranteed not ; to be large, the simple linear search is sufficient. ; 2a. Prepare the loop: edi will point to the current item of .Partitions ; array, ecx will be the current item, ebx will hold number of items left. mov edi, [esi+DISK.Partitions] mov ebx, [esi+DISK.NumPartitions] test ebx, ebx jz .partitionok .scan_existing: ; 2b. Get the next partition. mov ecx, [edi] add edi, 4 ; The range [.FirstSector, .FirstSector+.Length) must be either entirely to ; the left of [start, start+length) or entirely to the right. ; 2c. Subtract .FirstSector - start. The possible overflow distinguish between ; cases "to the left" (2e) and "to the right" (2d). mov eax, dword [ecx+PARTITION.FirstSector] mov edx, dword [ecx+PARTITION.FirstSector+4] sub eax, dword [start] sbb edx, dword [start+4] jb .less ; 2d. .FirstSector is greater than or equal to start. Check that .FirstSector ; is greater than or equal to start+length; the subtraction ; (.FirstSector-start) - length must not cause overflow. Go to 2g if life is ; good or to 2f in the other case. sub eax, dword [length] sbb edx, dword [length+4] jb .overlap jmp .next_existing .less: ; 2e. .FirstSector is less than start. Check that .FirstSector+.Length is less ; than or equal to start. If the addition (.FirstSector-start) + .Length does ; not cause overflow, then .FirstSector + .Length is strictly less than start; ; since the equality is also valid, use decrement preliminarily. Go to 2g or ; 2f depending on the overflow. sub eax, 1 sbb edx, 0 add eax, dword [ecx+PARTITION.Length] adc edx, dword [ecx+PARTITION.Length+4] jnc .next_existing .overlap: ; 2f. The partition overlaps with previously registered partition. Say warning ; and return with nothing done. dbgstr 'two partitions overlap, ignoring the last one' jmp .nothing .next_existing: ; 2g. The partition does not overlap with the current partition. Continue the ; loop. dec ebx jnz .scan_existing .partitionok: ; 3. The partition has passed tests. Reallocate the partitions array for a new ; entry. ; 3a. Call the allocator. mov eax, [esi+DISK.NumPartitions] inc eax ; one more entry shl eax, 2 ; each entry is dword call malloc ; 3b. Test the result. If failed, return with nothing done. test eax, eax jz .nothing ; 3c. Copy the old array to the new array. mov edi, eax push esi mov ecx, [esi+DISK.NumPartitions] mov esi, [esi+DISK.Partitions] rep movsd pop esi ; 3d. Set the field in the DISK structure to the new array. xchg [esi+DISK.Partitions], eax ; 3e. Free the old array. call free ; 4. Recognize the file system. ; 4a. Call the filesystem recognizer. It will allocate the PARTITION structure ; with possible filesystem-specific fields. call disk_detect_partition ; 4b. Check return value. If zero, return with list not changed; so far only ; the array was reallocated, this is ok for other code. test eax, eax jz .nothing ; 5. Insert the new partition to the list. stosd inc [esi+DISK.NumPartitions] ; 6. Return. .nothing: ret endp ; This is an internal function called from disk_add_partition. ; It tries to recognize the file system on the partition and allocates the ; corresponding PARTITION structure with filesystem-specific fields. disk_detect_partition: ; This function inherits the stack frame from disk_add_partition. In stdcall ; with ebp-based frame arguments start from ebp+8, since [ebp]=saved ebp ; and [ebp+4]=return address. virtual at ebp+8 .start dq ? .length dq ? end virtual ; When disk_add_partition is called, ebx contains a pointer to ; a two-sectors-sized buffer. This function saves ebx in the stack ; immediately before ebp. virtual at ebp-4 .buffer dd ? end virtual ; 1. Read the bootsector to the buffer. mov al, DISKFUNC.read mov ebx, [.buffer] add ebx, 512 push 1 stdcall disk_call_driver, ebx, dword [.start], dword [.start+4], esp ; 2. Run tests for all supported filesystems. If at least one test succeeded, ; go to 4. ; For tests: qword [ebp+8] = partition start, qword [ebp+10h] = partition ; length, [esp] = 0 if reading bootsector failed or 1 if succeeded, ; ebx points to the buffer for bootsector. call fat_create_partition test eax, eax jnz .success ; 3. No file system has recognized the volume, so just allocate the PARTITION ; structure without extra fields. push sizeof.PARTITION pop eax call malloc test eax, eax jz .nothing mov edx, dword [.start] mov dword [eax+PARTITION.FirstSector], edx mov edx, dword [.start+4] mov dword [eax+PARTITION.FirstSector+4], edx mov edx, dword [.length] mov dword [eax+PARTITION.Length], edx mov edx, dword [.length+4] mov dword [eax+PARTITION.Length+4], edx mov [eax+PARTITION.Disk], esi and [eax+PARTITION.FSUserFunctions], 0 .success: .nothing: ; 4. Return with eax = pointer to PARTITION or NULL. pop ecx ret ; This function is called from file_system_lfn. ; This handler gets the control each time when fn 70 is called ; with unknown item of root subdirectory. ; in: esi -> name ; ebp = 0 or rest of name relative to esi ; out: if the handler processes path, it must not return in file_system_lfn, ; but instead pop return address and return directly to the caller ; otherwise simply return dyndisk_handler: push ebx edi ; save registers used in file_system_lfn ; 1. Acquire the mutex. mov ecx, disk_list_mutex call mutex_lock ; 2. Loop over the list of DISK structures. ; 2a. Initialize. mov ebx, disk_list .scan: ; 2b. Get the next item. mov ebx, [ebx+DISK.Next] ; 2c. Check whether the list is done. If so, go to 3. cmp ebx, disk_list jz .notfound ; 2d. Compare names. If names match, go to 5. mov edi, [ebx+DISK.Name] push esi @@: ; esi points to the name from fs operation; it is terminated by zero or slash. lodsb test al, al jz .eoin_dec cmp al, '/' jz .eoin ; edi points to the disk name. inc edi ; edi points to lowercase name, this is a requirement for the driver. ; Characters at esi can have any register. Lowercase the current character. ; This lowercasing works for latin letters and digits; since the disk name ; should not contain other symbols, this is ok. or al, 20h cmp al, [edi-1] jz @b .wrongname: ; 2f. Names don't match. Continue the loop. pop esi jmp .scan .notfound: ; The loop is done and no name matches. ; 3. Release the mutex. call mutex_unlock ; 4. Return normally. pop edi ebx ; restore registers used in file_system_lfn ret ; part of 2d: the name matches partially, but we must check that this is full ; equality. .eoin_dec: dec esi .eoin: cmp byte [edi], 0 jnz .wrongname ; We found the addressed DISK structure. ; 5. Reference the disk. lock inc [ebx+DISK.RefCount] ; 6. Now we are sure that the DISK structure is not going to die at least ; while we are working with it, so release the global mutex. call mutex_unlock pop ecx ; pop from the stack saved value of esi ; 7. Acquire the mutex for media object. pop edi ; restore edi lea ecx, [ebx+DISK.MediaLock] call mutex_lock ; 8. Get the media object. If it is not NULL, reference it. xor edx, edx cmp [ebx+DISK.MediaInserted], dl jz @f mov edx, ebx inc [ebx+DISK.MediaRefCount] @@: ; 9. Now we are sure that the media object, if it exists, is not going to die ; at least while we are working with it, so release the mutex for media object. call mutex_unlock mov ecx, ebx pop ebx eax ; restore ebx, pop return address ; 10. Check whether the fs operation wants to enumerate partitions (go to 11) ; or work with some concrete partition (go to 12). cmp byte [esi], 0 jnz .haspartition ; 11. The fs operation wants to enumerate partitions. ; 11a. Only "list directory" operation is applicable to / path. Check ; the operation code. If wrong, go to 13. cmp dword [ebx], 1 jnz .access_denied ; 11b. If the media is inserted, use 'fs_dyndisk_next' as an enumeration ; procedure. Otherwise, use 'fs_dyndisk_next_nomedia'. mov esi, fs_dyndisk_next_nomedia test edx, edx jz @f mov esi, fs_dyndisk_next @@: ; 11c. Let the procedure from fs_lfn.inc do the job. jmp file_system_lfn.maindir_noesi .haspartition: ; 12. The fs operation has specified some partition. ; 12a. Store parameters for callback functions. push edx push ecx ; 12b. Store callback functions. push dyndisk_cleanup push fs_dyndisk mov edi, esp ; 12c. Let the procedure from fs_lfn.inc do the job. jmp file_system_lfn.found2 .access_denied: ; 13. Fail the operation with the appropriate code. mov dword [esp+32], ERROR_ACCESS_DENIED .cleanup: ; 14. Cleanup. mov esi, ecx ; disk*dereference assume that esi points to DISK .cleanup_esi: test edx, edx ; if there are no media, we didn't reference it jz @f call disk_media_dereference @@: call disk_dereference ; 15. Return. ret ; This is a callback for cleaning up things called from file_system_lfn.found2. dyndisk_cleanup: mov esi, [edi+8] mov edx, [edi+12] jmp dyndisk_handler.cleanup_esi ; This is a callback for enumerating partitions called from ; file_system_lfn.maindir in the case of inserted media. ; It just increments eax until DISK.NumPartitions reached and then ; cleans up. fs_dyndisk_next: cmp eax, [ecx+DISK.NumPartitions] jae .nomore inc eax clc ret .nomore: pusha mov esi, ecx call disk_media_dereference call disk_dereference popa stc ret ; This is a callback for enumerating partitions called from ; file_system_lfn.maindir in the case of missing media. ; In this case we create one pseudo-partition. fs_dyndisk_next_nomedia: cmp eax, 1 jae .nomore inc eax clc ret .nomore: pusha mov esi, ecx call disk_dereference popa stc ret ; This is a callback for doing real work with selected partition. ; Currently this is just placeholder, since no file systems are supported. ; edi = esp -> {dd fs_dyndisk, dd dyndisk_cleanup, dd pointer to DISK, dd media object} ; ecx = partition number, esi+ebp = ASCIIZ name fs_dyndisk: dec ecx ; convert to zero-based partition index pop edx edx edx eax ; edx = pointer to DISK, eax = NULL or edx test eax, eax jz .nomedia .main: cmp ecx, [edx+DISK.NumPartitions] jae .notfound mov eax, [edx+DISK.Partitions] mov eax, [eax+ecx*4] mov edi, [eax+PARTITION.FSUserFunctions] test edi, edi jz .nofs mov ecx, [ebx] cmp [edi], ecx jbe .unsupported push edx push ebp mov ebp, eax call dword [edi+4+ecx*4] pop ebp pop edx mov dword [esp+32], eax mov dword [esp+20], ebx .cleanup: mov esi, edx call disk_media_dereference call disk_dereference ret .nofs: mov dword [esp+32], ERROR_UNKNOWN_FS jmp .cleanup .notfound: mov dword [esp+32], ERROR_FILE_NOT_FOUND jmp .cleanup .unsupported: mov dword [esp+32], ERROR_UNSUPPORTED_FS jmp .cleanup .nomedia: test ecx, ecx jnz .notfound test byte [edx+DISK.DriverFlags], DISK_NO_INSERT_NOTIFICATION jz .deverror ; if the driver does not support insert notifications and we are the only fs ; operation with this disk, issue the fake insert notification; if media is ; still not inserted, 'disk_media_changed' will detect this and do nothing lea ecx, [edx+DISK.MediaLock] call mutex_lock cmp [edx+DISK.MediaRefCount], 1 jnz .noluck call mutex_unlock push edx stdcall disk_media_changed, edx, 1 pop edx lea ecx, [edx+DISK.MediaLock] call mutex_lock cmp [edx+DISK.MediaInserted], 0 jz .noluck lock inc [edx+DISK.MediaRefCount] call mutex_unlock xor ecx, ecx jmp .main .noluck: call mutex_unlock .deverror: mov dword [esp+32], ERROR_DEVICE mov esi, edx call disk_dereference ret ; This function is called from file_system_lfn. ; This handler is called when virtual root is enumerated ; and must return all items which can be handled by this. ; It is called several times, first time with eax=0 ; in: eax = 0 for first call, previously returned value for subsequent calls ; out: eax = 0 => no more items ; eax != 0 => buffer pointed to by edi contains name of item dyndisk_enum_root: push edx ; save register used in file_system_lfn mov ecx, disk_list_mutex ; it will be useful ; 1. If this is the first call, acquire the mutex and initialize. test eax, eax jnz .notfirst call mutex_lock mov eax, disk_list .notfirst: ; 2. Get next item. mov eax, [eax+DISK.Next] ; 3. If there are no more items, go to 6. cmp eax, disk_list jz .last ; 4. Copy name from the DISK structure to edi. push eax esi mov esi, [eax+DISK.Name] @@: lodsb stosb test al, al jnz @b pop esi eax ; 5. Return with eax = item. pop edx ; restore register used in file_system_lfn ret .last: ; 6. Release the mutex and return with eax = 0. call mutex_unlock xor eax, eax pop edx ; restore register used in file_system_lfn ret