发信人: ikoo()
整理人: simonshium(1999-06-30 20:19:26), 站内信件
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VIRTUAL DEVICE SEGMENTS
Vitual Devices can have any combination of the following five segments:
Segment Description
VxD_CODE Specifies the protected-mode code segment. This required segment
contains the device control procedure, callback procedures, services,
and API procedures of the virtual device. Use the VxD_CODE_SEG
and VxD_CODE_ENDS macros to define the start and end of
definitions for this segment. This segment is also named_LTEXT.
VxD_DATA Specifies the protected-mode data segment. This required segment
contains the device descriptor block, service table, and any global
data for the virtual device. Use the VxD_DATA_SEG and
VxD_DATA_ENDS macros to define the start and end of definitions
for this segment. This segment is also named _LDATA.
VxD_ICODE Specifies the protected-mode initialization code segment. This
optional egment usually contains the procedures and services that
are used only during initialization of the virtual device. The VMM
discards this segment after the Init_Complete message. Use the
VxD_ICODE_SEG and VxD_ICODE_ENDS macros to define the start
and end of definitions for this segment. This segment is also
named_ITEXT.
VxD_IDATA Specifies the protected-mode initialization data segment. This optional
segment usually contains the data used by the initialization
procedures and services. The VMM discards this segment after the
Init_Complete message. Use the VxD_IDATA_SEG and
VxD_IDATA_ENDS macros to define the start and end of definitions
for this segment. This segment is also named _IDATA.
VxD_REAL_INIT Specifies the real-mode initialization segment. This optional segment
contains the real-mode initialization procedure and data. The VMM
calls this procedure before loading the rest of the virtual device, then
discards this segment after the procedure returns. Use the
VxD_REAL_INIT_SEG and VxD_REAL_INIT_ENDS macors to
define the start and end of definitions for the real-mode initialization
segment. This segment is also named _RTEXT.
All code and data segments, except the real-mode initialization segment, are 32-bit
flat model, protected-mode segments. This means procedures and data defined in the
protected-mode segments have 32-bitoffsets. When the VMM loads the virtual devie,
it fixes all offsets according to the virtual device's actual position in memory. for this
reason, the OFFSET32 macro should be used in the protected-mode segments
wherever the OFFSET directive would ordinarily be used. The OFFSET32 macro
defines offsets for which the linker produces correct offset-fixup information.
Virtual devices cannot change the CS,DS,ES,SS segment registers. Virtual devices
can use the FS nad GS segment registers.
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