I386_GET_LDT(2) OpenBSD Programmer's Manual (i386) I386_GET_LDT(2)NAME
i386_get_ldt, i386_set_ldt - manage i386 per-process Local Descriptor
Table entries
SYNOPSIS
#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);
DESCRIPTIONi386_get_ldt() returns a list of the i386 descriptors in the current
process' LDT. i386_set_ldt() 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 a
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
Upon successful completion, i386_get_ldt() returns the number of i386
descriptors copied into descs from the current process' LDT. Otherwise,
a value of -1 is returned and the global variable errno is set to
indicate the error.
Upon successful completion, i386_set_ldt() returns the first selector
set; 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.
ERRORSi386_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
Intel, i386 Microprocessor Programmer's Reference Manual.
WARNING
You can really hose your process using this.
OpenBSD 4.9 May 31, 2007 OpenBSD 4.9