NAME

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

LIBRARY

i386 Architecture Library (libi386, -li386)

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);

DESCRIPTION

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 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.

RETURN VALUES

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

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

i386 Microprocessor Programmer's Reference Manual, Intel

WARNING

You can really hose your process using this.