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431 serge 1
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;                                                              ;;
5565 serge 3
;; Copyright (C) KolibriOS team 2013-2015. All rights reserved. ;;
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;; Distributed under terms of the GNU General Public License    ;;
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;;                                                              ;;
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;; RAMDISK functions                                            ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
1 ha 8
 
593 mikedld 9
$Revision: 5565 $
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4287 Serge 11
iglobal
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align 4
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ramdisk_functions:
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        dd      .size
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        dd      0       ; no close() function
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        dd      0       ; no closemedia() function
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        dd      ramdisk_querymedia
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        dd      ramdisk_read
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        dd      ramdisk_write
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        dd      0       ; no flush() function
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        dd      ramdisk_adjust_cache_size
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.size = $ - ramdisk_functions
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endg
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4287 Serge 25
iglobal
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align 4
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ramdisk_actual_size     dd      RAMDISK_CAPACITY
171 diamond 28
endg
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4287 Serge 30
; This function is called early in boot process.
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; It creates filesystem /rd/1 based on raw image data loaded by somebody before
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; to memory named as RAMDISK with max size RAMDISK_CAPACITY, may be less.
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proc ramdisk_init
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iglobal
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ramdisk_name    db      'rd',0
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endg
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        push    ebx esi ; save used registers to be stdcall
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; 1. Register the device and the (always inserted) media in the disk subsystem.
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        stdcall disk_add, ramdisk_functions, ramdisk_name, 0, 0
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        test    eax, eax
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        jz      .fail
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        mov     ebx, eax
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        stdcall disk_media_changed, eax, 1
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; 2. We don't know actual size of loaded image,
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; so try to calculate it using partition structure,
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; assuming that file systems fill the real size based on contents of the partition.
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; 2a. Prepare for loop over partitions.
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        xor     ecx, ecx
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        xor     edx, edx
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; 2b. Check that at least one partition was recognized.
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        cmp     [ebx+DISK.NumPartitions], ecx
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        jz      .fail
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; 2c. Loop over partitions.
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.partitions:
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; For every partition, set edx to maximum between edx and end of partition.
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        mov     esi, [ebx+DISK.Partitions]
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        mov     esi, [esi+ecx*4]
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        mov     eax, dword [esi+PARTITION.FirstSector]
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        add     eax, dword [esi+PARTITION.Length]
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        cmp     eax, edx
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        jb      @f
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        mov     edx, eax
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@@:
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        inc     ecx
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        cmp     ecx, [ebx+DISK.NumPartitions]
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        jb      .partitions
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; 3. Reclaim unused memory, if any.
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        mov     [ramdisk_actual_size], edx
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        add     edx, 7  ; aligning up
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        shr     edx, 3  ; 512-byte sectors -> 4096-byte pages
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        mov     esi, RAMDISK_CAPACITY / 8       ; aligning down
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        sub     esi, edx
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        jbe     .no_reclaim
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        shl     edx, 12
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        add     edx, RAMDISK - OS_BASE
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@@:
4287 Serge 77
        mov     eax, edx
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        call    free_page
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        add     edx, 0x1000
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        dec     esi
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        jnz     @b
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.no_reclaim:
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        pop     esi ebx ; restore used registers to be stdcall
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        ret
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.fail:
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        dbgstr 'Failed to initialize ramdisk'
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        pop     esi ebx ; restore used registers to be stdcall
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        ret
4287 Serge 89
endp
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4287 Serge 91
; Returns information about disk media.
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proc ramdisk_querymedia
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  virtual at esp+4
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    .userdata dd ?
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    .info dd ?
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  end virtual
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; Media is always present, sector size is always 512 bytes.
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        mov     edx, [.userdata]
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        mov     ecx, [.info]
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        mov     [ecx+DISKMEDIAINFO.Flags], 0
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        mov     [ecx+DISKMEDIAINFO.SectorSize], 512
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        mov     eax, [ramdisk_actual_size]
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        mov     dword [ecx+DISKMEDIAINFO.Capacity], eax
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        mov     dword [ecx+DISKMEDIAINFO.Capacity+4], 0
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; Return zero as an indicator of success.
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        xor     eax, eax
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        retn    8
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endp
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4287 Serge 110
; Common procedure for reading and writing.
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; operation = 0 for reading, operation = 1 for writing.
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; Arguments of ramdisk_read and ramdisk_write are the same.
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macro ramdisk_read_write operation
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{
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        push    esi edi         ; save used registers to be stdcall
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        mov     esi, [userdata]
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        mov     edi, [numsectors_ptr]
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; 1. Determine number of sectors to be transferred.
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; This is either the requested number of sectors or number of sectors
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; up to the disk boundary, depending of what is less.
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        xor     ecx, ecx
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; 1a. Test whether [start_sector] is less than RAMDISK_CAPACITY.
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; If so, calculate number of sectors between [start_sector] and RAMDISK_CAPACITY.
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; Otherwise, the actual number of sectors is zero.
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        cmp     dword [start_sector+4], ecx
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        jnz     .got_number
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        mov     eax, [ramdisk_actual_size]
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        sub     eax, dword [start_sector]
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        jbe     .got_number
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; 1b. Get the requested number of sectors.
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        mov     ecx, [edi]
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; 1c. If it is greater than number of sectors calculated in 1a, use the value
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; from 1a.
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        cmp     ecx, eax
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        jb      .got_number
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        mov     ecx, eax
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.got_number:
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; 2. Compare the actual number of sectors with requested. If they are
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; equal, set eax (it will be the returned value) to zero. Otherwise,
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; use DISK_STATUS_END_OF_MEDIA.
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        xor     eax, eax
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        cmp     ecx, [edi]
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        jz      @f
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        mov     al, DISK_STATUS_END_OF_MEDIA
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@@:
4287 Serge 146
; 3. Store the actual number of sectors.
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        mov     [edi], ecx
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; 4. Calculate source and destination addresses.
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if operation = 0 ; reading?
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        mov     esi, dword [start_sector]
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        shl     esi, 9
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        add     esi, RAMDISK
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        mov     edi, [buffer]
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else ; writing?
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        mov     edi, dword [start_sector]
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        shl     edi, 9
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        add     edi, RAMDISK
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        mov     esi, [buffer]
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end if
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; 5. Calculate number of dwords to be transferred.
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        shl     ecx, 9-2
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; 6. Copy data.
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        rep movsd
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; 7. Return. The value in eax was calculated in step 2.
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        pop     edi esi         ; restore used registers to be stdcall
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}
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; Reads one or more sectors from the device.
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proc ramdisk_read userdata:dword, buffer:dword, start_sector:qword, numsectors_ptr:dword
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        ramdisk_read_write 0
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        ret
4287 Serge 172
endp
83 diamond 173
 
4287 Serge 174
; Writes one or more sectors to the device.
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proc ramdisk_write userdata:dword, buffer:dword, start_sector:qword, numsectors_ptr:dword
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        ramdisk_read_write 1
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        ret
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endp
83 diamond 179
 
4287 Serge 180
; The kernel calls this function when initializing cache subsystem for
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; the media. This call allows the driver to adjust the cache size.
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proc ramdisk_adjust_cache_size
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  virtual at esp+4
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    .userdata dd ?
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    .suggested_size dd ?
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  end virtual
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; Since ramdisk does not need cache, just return 0.
3555 Serge 188
        xor     eax, eax
4287 Serge 189
        retn    8
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endp