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include vmm.inc VMMcall _MapIntoV86, <hMem, VM, VMLinPgNum, nPages, PageOff, flags> or eax, eax ; nonzero if pages mapped, zero if error jz not_mapped |
The _MapIntoV86 service maps one or more pages of a memory block into the V86 address space of the specified virtual machine.
hMem
Specifies the handle identifying the memory block to map. This handle must have been previously created using the PageAllocate or PageReAllocate service.
VM
Specifies a handle identifying the virtual machine for which to map the memory.
VMLinPgNum
Specifies the linear page number of a V86 address. The service maps the specified pages to this address. This parameter must be a page number in the range 10h through 10Fh.
nPages
Specifies the number of pages to map.
PageOff
Specifies the offset in pages from the beginning of the memory block to the first page to map.
flags
Specifies the operation flags. This parameter can be the following value:
| Value | Meaning |
| PageDEBUGNulFault | Enables page faults for system nul pages. If the memory block contains system nul pages, a page fault occurs whenever a nul page is accessed. This value only applies when running the debugging version of the Windows virtual machine manager. If this value is not given or the debugging version is not running, no page faults occur. |
All other values are reserved.
The EAX register contains a nonzero value if the map is successful. Otherwise, EAX contains zero to indicate an error such as an invalid memory handle, an invalid virtual machine handle, an illegal map range, a size discrepancy, or insufficient memory for locking.
A virtual device typically uses this service to map buffers having protected-mode addresses into the V86 address space. This gives software running in the virtual machine a means of passing data to and receiving data from the virtual device.
The service returns an error if the sum of the PageOff and nPages parameters is greater than the size of the memory block.
Although a virtual device can map the same page into multiple addresses in the V86 address space, this is not recommended.
For each mapped page, this service sets the P_USER, P_PRES, and P_WRITE bits but clears the P_DIRTY and P_ACC bits. The service sets the page type to be identical to the page type for the pages at the specified protected-mode linear address. Although the memory block to be mapped can have PG_SYS page type, it is not recommended.
If the virtual page swap device uses MS-DOS or BIOS functions to write to the hardware, _MapIntoV86 automatically locks the mapped pages and unlocks any previously mapped pages. If the virtual page swap device writes directly to the hardware, this service neither lock nor unlocks the pages.
If a virtual device no longer needs the mapped region, it should map the system nul page into the V86 address space using the _MapIntoV86 service. A virtual device can retrieve the handle for the system nul page using the _GetNulPageHandle service.
This service accepts V86 page numbers between 10h and the page number returned by the _GetFirstV86Page service. This supports virtual devices that use the _Allocate_Global_V86_Data_Area service. Mapping a region which spans across the first V86 page is not allowed. Mapping pages in this region to other addresses can easily crash the system and should be avoided.
EAX
_Allocate_Global_V86_Data_Area, _GetFirstV86Page, _GetNulPageHandle, _LinMapIntoV86