FSH_SEGALLOC - Allocate a GDT or LDT segment

Purpose   

This function allocates a GDT or LDT selector. The selector will have 
read/write access. An FSD may call this function. 

Calling Sequence   

int far pascal FSH_SEGALLOC(flags, cbSeg, pSel)

unsigned short flags;
unsigned long cbSeg;
unsigned short far * pSel;

Where   

flags indicate GDT/LDT, protection ring, swappable/non-swappable. 

Bit 0x0001 off indicates GDT selector returned. 
Bit 0x0001 on indicates LDT selector returned. 
Bit 0x0002 off indicates non-swappable memory. 
Bit 0x0002 on indicates swappable memory. 
Bits 13 and 14 are the desired ring number. 

All other bits are reserved and must be zero. 

cbSeg is the length of the segment. 

pSel is the far address of the location where the allocated selector will 
be stored. 
  

Returns   

If no error is detected, a zero error code is returned. If an error is 
detected, one of the following error codes is returned: 

oERROR_INTERRUPT 
the current thread received a signal. 

oERROR_INVALID_PARAMETER 
the reserved bits in flags are set or requested size is too large. 

oERROR_NOT_ENOUGH_MEMORY 
too much memory is allocated. 
  

Remarks   

It is strongly suggested that FSDs allocate all their data at protection 
level 0 for maximum protection from user programs. 

GDT selectors are a scarce resource; the FSD must be prepared to expect an 
error for allocation of a GDT segment. The FSD should limit itself to a 
maximum of 10 GDT segments. It is suggested that a large segment be 
allocated for each type of data and divided into per-process records. 

FSH_SEGALLOC may block. 

Take care to avoid deadlocks between swappable segments and swapper 
requests . 

Note:   OS/2 does not validate input parameters. An FSD, therefore, should 
call FSH_PROBEBUF where appropriate.