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I386_GET_LDT(2)                            BSD System Calls Manual                           I386_GET_LDT(2)

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

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <architecture/i386/table.h>
     #include <i386/user_ldt.h>

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

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

DESCRIPTION
     The i386_get_ldt() system call will return the list of i386 descriptors that the process has in its
     LDT.  The i386_set_ldt() system call 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 code_desc_t, data_desc_t or call_gate_t and are defined in
     <architecture/i386/desc.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 return its selector number.

     If num_descs is 1, start_sels is valid, and descs is NULL, then i386_set_ldt() will free that descrip-tor descriptor
     tor (making it available to be reallocated 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 descriptors currently in the LDT.  The
     i386_set_ldt() system call returns the first selector set.  In the case when a descriptor is allocated
     by the kernel, its number will be returned.  Otherwise, a value of -1 is returned and the global vari-able variable
     able 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 circumvent protection or cause a
                        failure.

SEE ALSO
     i386 Microprocessor Programmer's Reference Manual, Intel

WARNING
     You can really hose your process using this.

BSD                                          September 20, 1993                                          BSD