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);
DESCRIPTION
i386_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.
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
Intel, i386 Microprocessor Programmer's Reference Manual.
WARNING
You can really hose your process using this.