2 .\" Copyright (c) 1996 Joerg Wunsch
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35 .Nd I/O privilege file
44 struct iodev_pio_req {
54 is a controlled security hole that allows a process to gain I/O
56 (which are normally reserved for kernel-internal code).
57 This can be useful in order to write userland
58 programs that handle some hardware directly.
60 The usual operations on the device are to open it via the
62 interface and to send I/O requests to the file descriptor using the
68 requests available for
70 are mostly platform dependent, but there are also some in common between
74 is used by all the architectures in order to request that an I/O operation
76 It takes a 'struct iodev_pio_req' argument that must be previously setup.
80 member specifies the type of operation requested.
82 .Bl -tag -width IODEV_PIO_WRITE
84 The operation is an "in" type.
85 A value will be read from the specified port
88 member) and the result will be stored in the
91 .It Dv IODEV_PIO_WRITE
92 The operation is a "out" type.
93 The value will be fetched from the
95 member and will be written out to the specified port (defined as the
102 member specifies the size of the operand to be read/written, expressed
105 In addition to any file access permissions on
107 the kernel enforces that only the super-user may open this device.
111 interface used to be very i386 specific and worked differently.
112 The initial implementation simply raised the
114 of the current thread when
116 was called on the device.
117 This behaviour is retained in the current implementation as legacy
118 support for both i386 and amd64 architectures.
121 .Xr i386_get_ioperm 2 ,
122 .Xr i386_set_ioperm 2 ,