NAME    [Toc]    [Back]

     i386_get_ldt, i386_set_ldt - manage i386  per-process  Local
Descriptor
     Table entries

SYNOPSIS    [Toc]    [Back]

     #include <sys/types.h>
     #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    [Toc]    [Back]

     i386_get_ldt() will return the list of i386 descriptors that
the process
     has in its LDT.  i386_set_ldt() will set a list of i386  descriptors for
     the  current  process  in  its  LDT.  Both routines accept a
starting selector
     number start_sel, an array of memory that will  contain  the
descriptors to
     be  set  or returned descs, and the number of entries to set
or return
     num_sels.

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

     Before  this API can be used the functionality has to be enabled using the
     machdep.userldt sysctl(8) variable.

     Note: Code using the i386_get_ldt() and i386_set_ldt() functions must be
     compiled using -li386.

RETURN VALUES    [Toc]    [Back]

     Upon  successful completion, i386_get_ldt() returns the number of descriptors
 currently in the LDT.  i386_set_ldt() returns the first
selector
     set.   Otherwise,  a  value of -1 is returned and the global
variable errno
     is set to indicate the error.

ERRORS    [Toc]    [Back]

     i386_get_ldt() and i386_set_ldt() will fail if:

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

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

REFERENCES    [Toc]    [Back]

     Intel, i386 Microprocessor Programmer's Reference Manual.

WARNING    [Toc]    [Back]

     You can really hose your process using this.

OpenBSD     3.6                       September     20,      1993