Computer Systems and Multimedia

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Computer Systems and Multimedia

• WinIO

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WinIo

• Introduction
• A problem that plagues windows NT/2000 and
  windows XP, is its strict control over I/o ports.
• Windows NT/2000/XP will cause an exception
  (privilege instruction) if an attempt is made to
  access a port that it is not privileged to talk
  to
• Accessing I/O ports is governed by two events.
  The I/O privilege level (IOPL) in the EFLAGS
  register and the I/O permission bit map of a task
  state segment (TSS)
• Under windows NT, there are two I/O privilege
  levels used, level 0 and level 3. User mode
  programs will run in level 3 (lesser privilege),
  while device drivers and the kernel will run in
  level 0

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WinIo - contd

• This allows trusted operating system and drivers
  running in kernel mode to access the ports, while
  preventing less trusted user mode processes from
  touching the I/O ports and causing conflicts.
• All user mode program should talk to a device
  driver which arbitrates access
• The I/O permission bit map can be used to allow
  programs not privilege enough (i.e user mode
  programs) the ability to access the I/O ports
• When an I/O instruction is executed, the
  processor will first check if the task is
  privilege enough to access the port. Should be
  the case, the I/O instruction will be executed.
  However if the task is not allowed to so I/O, the
  processor will then check the I/O permission bit
  map
• The I/O permission bit map uses a single bit to
  represent each I/O address
• If the bit corresponding to a port is set, then
  the instruction will generate an exception.
  However, if the bit is clear then the I/O
  operation will proceed
• This gives a mean to allow certain processes to
  access certain ports

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WinIO

• The WinIo library allows 32 bit windows
  applications to directly access I/O ports and
  physical memory
• It bypasses windows protection mechanisms by
  using a combination of kernel mode device driver
  and several low level programming techniques
• The functions available in WinIO are as follows
• InitializeWinIo PROTO
• Parameter none
• Returns true if succeeds, otherwise false
• This function must be called before using any
  other functions in the library
• ShutdownWinIo PROTO
• Parameter none
• Return none
• This function must be called before terminating
  the application in case the WinIo library is no
  longer required. This shuts down the WinIo
  library and frees the resources which were
  allocated by a call to the function

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WinIO - contd

• GetPortValue PROTO portaddrDWORD,lpPortValueDWO
  RD, \ bSizeDWORD
• Parameter
• portaddr I/O port address
• lpPortValue pointer to a variable that
  receives the value from the port
• bSize Number of bytes to read can either be 1,
  2 or 4
• Returns true if succeeds, otherwise false
• This function reads a byte, a word or a double
  word from the specified port
• SetPortValue PROTO portaddrDWORD,PortValueDWORD
  , \ bSizeDWORD
• Parameter
• portaddr I/O port address
• PortValue Value to be written to the port
• bSize Number of bytes to read can either be 1,
  2 or 4
• Returns true if succeeds, otherwise false
• This function writes a byte, a word or a double
  word to the specified port

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WinIO - contd

• GetPhysLong PROTO lpPhysaddrDWORD,lpPhysValDWOR
  D
• Parameter
• lpPhysaddr pointer to physical address
• lpPhysVal pointer to DWORD variable that
  receives value from physical memory
• Returns true if succeeds, otherwise false
• This function reads a double word from the
  specified memory location
• SetPhysLong PROTO lpPhysaddrDWORD,PhysValDWORD
• Parameter
• lpPhysaddr pointer to physical address
• PhysVal DWORD value to be written to physical
  memory location
• Returns true if succeeds, otherwise false
• This function writes a double word to the
  specified memory location

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WinIO - contd

• MapPhysToLin PROTO lpPhysaddrDWORD,PhysSizelDWO
  RD,\ lpPhysMemHandleDWORD
• Parameter
• lpPhysaddr pointer to physical address
• PhysSize number of bytes to map
• lpPhysMemHandle points to a variable that will
  receive the physical memory section handle if the
  call is successful
• Returns linear address corresponding to physical
  address if succeeds, otherwise NULL
• This function maps a region of physical memory to
  linear address space
• UnmapPhysicalMemory PROTO lpPhysMemHandle
  DWORD, linAddrDWORD
• Parameter
• lpPhysMemHandle handle to physical memory
  section from above
• linAddr linear address return from above
• Returns true if succeeds, otherwise false
• This function unmaps a region of physical memory
  (previously mapped)

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WinIO - contd

• Using WinIo
• Place winio.dll, winio.vxd and winio.sys in the
  directory where the applications executable file
  reside
• Include winio.lib in the application using
  includelib directive or include winio.lib in the
  link command line
• Add header file winio.inc in the application
  using include directive
• Call InitializeWinIo
• Call the librarys functions to access port or
  physical memory
• Call ShutdownWinIo

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WinIO - contd

• Include \include\Irvine32.inc
• includelib \lib\kernel32.lib
• includelib \lib\user32.lib
• includelib WinIo.lib ltltltltltltltltltltltltltltltltltltltltltlt
  Library
• include WinIo.inc ltltltltltltltltltltltltltltltltltltltltltlt Include
  file
• .data
• value DWORD ?
• str BYTE Value returned
• .code
• start
• invoke InitializeWinIo
• invoke SetPortVal, 378h, 0ffh, 1
• invoke GetPortVal,378h,addr value,1
• mov edx,offset str
• call writestring
• mov eax,value
• call writehex
• invoke ShutdownWinIo
• invoke ExitProcess, NULL

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WinIO - contd

• Parallel Interface (Port)
• Originally designed for printers
• Attach via 25 pin or Centronics connector
• Provides 8 bit I/O
• Provides TTL level (5 V) external I/O
• Major signals

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WinIO - contd

• Provides easy interface to PC
• Just redefine meaning of signals and attach
  hardware to PC
• PC can have up to three LPT devices
• Each device has a unique port I/O address
• Most Computers have LPT1 as the printer port

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WinIO - contd

• Control Port (37Ah)

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WinIO - contd

• Status Port (379h)

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WinIO - contd

• Writing to Parallel Port

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WinIO - contd

• includelib \lib\kernel32.lib
• includelib \lib\user32.lib
• includelib WinIo.lib ltltltltltltltltltltltltltltltltltltltltltlt
  Library
• include WinIo.inc ltltltltltltltltltltltltltltltltltltltltltlt Include
  file
• .data
• portdata DWORD ?
• value DWORD ?
• .code
• start
• invoke InitializeWinIo
• invoke SetPortVal, 378h, portdata, 1 send data
  to port output
• invoke GetPortVal,379h,addr value,1 get status
• mov al,byte ptr value
• again
• test al,80h test busy
• jz again
• invoke SetPortVal,37Ah,0dh,1 send strobe (low)
• invoke SetPortVal,37Ah,0ch,1 pull strobe high
• invoke ShutdownWinIo

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WinIO - contd

• Serial Interface (Port)
• Implemented as COM1 and COM2
• Address of COM1 port

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WinIO - contd

• Transmitter Holding Register 3F8 (DLAB0)
• Contains character to be sent serially (write)
• Receiver Buffer Register 3F8 (DLAB0)
• Contains character received (read)
• Divisor Latch LSB 3F8 (DLAB1)
• Contains lower divisor
• Divisor Latch LSB 3F9 (DLAB1)
• Contains upper divisor
• Divisor Input frequency /(baud rate16)

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WinIO - contd

• Interrupt Enable Register 3F9 (DLAB0)
• Interrupt Identification Register 3FA
• Bit 1 bit 0
• 0 0 Receiver Line Status
• 0 1 Received Data Available
• 1 0 Transmitter Holding Register empty
• 1 1 Modem Status

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WinIO - contd

• Line Control Register 3FB
• bit 1 bit 0 bit 2
• 0 0 5 bits 0 1 stop bit
• 0 1 6 bits 1 2 stop bits
• 1 0 7 bits
• 1 1 8 bits
• bit 4 bit 3
• 0 0 no parity
• 0 1 odd parity
• 1 0 no parity
• 1 1 even parity

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WinIO - contd

• Modem Control Register 3FC
• Line Status Register 3FD
• Divisor Latch LSB 3FE

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WinIO - contd

• Forcing DTR and RTS (without using modem)
• Invoke SetPortVal,3FCh,03h,1 modem control
  register at 3FC
• writing 1 to bit and bit0 forces
• DTR and CTS to 0
• Initialization
• Invoke SetPortVal,3FBh,83h,1 no parity,stop
  bit 1, data 8 bit,dlab1
• Invoke SetPortVal,3F8h,0Ch,1 lower divisor
  number
• Invoke SetPortVal,3F9h,00h,1 upper divisor
  number, baud rate 9600
• Invoke SetPortVal,3FCh,7Fh,1 reset dlab
• Receiving and Sending Character (Polling)
• sin
• invoke GatePortVal,3FDh,addr status,1
• mov al,byte ptr status
• test al,1 check DR 1, Data received?
• jz sout
• invoke GetPortVal,3F8h,addr dataIn,1 read data
• jmp sin

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WinIO - contd

• sout
• test al,20h check THRE 1, to send
• jz sin
• invoke SetPortVal,3F8h,portdata,1 send data
• jmp sin