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I386_GET_LDT(2) 	       System Calls Manual		 I386_GET_LDT(2)

NAME
     i386_get_ldt,  i386_set_ldt -- manage i386 per-process Local Descriptor Ta-
     ble entries

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <machine/segments.h>
     #include <machine/sysarch.h>

     int
     i386_get_ldt(int start_sel, union descriptor *descs, int num_sels);

     int
     i386_set_ldt(int start_sel, union descriptor *descs, int num_sels);

DESCRIPTION
     The i386_get_ldt() system call returns a list of the  i386  descriptors  in
     the  current  process'  LDT.  The i386_set_ldt() system call sets a list of
     i386 descriptors in the current process' LDT.  For both routines, start_sel
     specifies the index of the selector in the LDT at which to begin and  descs
     points to an array of num_sels descriptors to be set or returned.

     Each  entry  in  the  descs  array  can  be  either a segment_descriptor or
     gate_descriptor and are defined in <i386/segments.h>.  These structures are
     defined by the architecture as disjoint bit-fields, so care must  be  taken
     in constructing them.

     If start_sel is LDT_AUTO_ALLOC, num_sels is 1 and the descriptor pointed to
     by  descs	is legal, then i386_set_ldt() will allocate a descriptor and re-
     turn its selector number.

     If  num_descs  is	1,  start_sels	is  valid,  and  descs	is  NULL,   then
     i386_set_ldt() will free that descriptor (making it available to be reallo-
     cated again later).

     If  num_descs  is	0,  start_sels is 0 and descs is NULL then, as a special
     case, i386_set_ldt() will free all descriptors.

RETURN VALUES
     Upon successful completion, i386_get_ldt() returns the number  of	descrip-
     tors  currently  in  the  LDT.   The i386_set_ldt() system call returns the
     first selector set on success.  If the kernel allocated a descriptor in the
     LDT, the allocated index is returned.  Otherwise, a value of -1 is returned
     and the global variable errno is set to indicate the error.

ERRORS
     The i386_get_ldt() and i386_set_ldt() system calls will fail if:

     [EINVAL]		An  inappropriate  value  was  used  for  start_sel   or
			num_sels.

     [EACCES]		The caller attempted to use a descriptor that would cir-
			cumvent protection or cause a failure.

SEE ALSO
     i386 Microprocessor Programmer's Reference Manual, Intel

WARNING
     You can really hose your process using this.

FreeBSD 8.2			October 14, 2006		 I386_GET_LDT(2)
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