MFSH_CALLRM - Put machine in real mode

Purpose   

Put the machine into real mode, call the specified routine, put the 
machine back into protect mode, and return. 

Calling Sequence   

int far pascal MFSH_CALLRM(plRoutine)

unsigned long far * plRoutine;

Where   

plRoutine is a pointer to a double word which contains the VIRTUAL address 
of the routine to call. 
  

Returns   

There are no error returns. 

Remarks   

Only registers DS and SI will be preserved between the caller and the 
target routine. The selector in DS will be converted to a segment before 
calling the target routine. Arguments may not be passed on the stack since 
a stack switch may occur. 

This helper allows the mini-FSD to access the ROM BIOS functions which 
typically run in real mode only. Great care must be taken in using this 
function since selectors used throughout the system are meaningless in 
real mode. While in real mode, no calls to any helpers may be made.