|
include vmm.inc mov eax, Service ; specifies the service to hook mov esi, OFFSET32 HookProc ; points to the hook procedure to install VMMcall Hook_Device_Service jc not_installed ; carry flag set if error mov [Real_Proc], esi |
The Hook_Device_Service service allows one virtual device to monitor or replace the services of another virtual device, or of the VMM itself.
Service
Specifies the virtual device or VMM service to hook.
HookProc
Points to the hook procedure to install. The hook procedure is called with the same parameters as the service specified by the Service parameter.
The carry flag is clear and the ESI register contains the address of the service specified by the Service parameter if this service is successful. Otherwise, the carry flag is set to indicate an error.
Virtual devices that use this service must use extreme care to preserve the full functionality of the virtual device whose services are monitored or replaced.
More than one virtual device can hook a device service. The last hook installed is the first one called.
The hook procedure must save and restore registers that are not modified by the hooked service. Also, if flags are a passed as an entry or exit parameter, the hook procedure must also preserve the flags.
If the hooked service uses the C calling convention, the hook procedure must copy the entire parameter stack frame before attempting to call the hooked service.
ESI, Flags