NetBSD/lib/libarch/i386/i386_get_ldt.2

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.\"     from: @(#)fork.2	6.5 (Berkeley) 3/10/91
.\"	$NetBSD: i386_get_ldt.2,v 1.13 2003/08/07 16:42:00 agc Exp $
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.Dd September 20, 1993
.Dt I386_GET_LDT 2 i386
.Os
.Sh NAME
.Nm i386_get_ldt ,
.Nm i386_set_ldt
.Nd manage i386 per-process Local Descriptor Table entries
.Sh LIBRARY
.Lb libi386
.Sh SYNOPSIS
.In sys/types.h
.In machine/segments.h
.In machine/sysarch.h
.Ft int
.Fn i386_get_ldt "int start_sel" "union descriptor *descs" "int num_sels"
.Ft int
.Fn i386_set_ldt "int start_sel" "union descriptor *descs" "int num_sels"
.Sh DESCRIPTION
.Fn i386_get_ldt
will return the list of i386 descriptors that the process has in its
LDT.
.Fn i386_set_ldt
will set a list of i386 descriptors for the current process in its
LDT.
Both routines accept a starting selector number
.Fa start_sel
, an array of memory that
will contain the descriptors to be set or returned
.Fa descs
, and the number of entries to set or return
.Fa num_sels .
.Pp
The argument
.Fa descs
can be either segment_descriptor or gate_descriptor and are defined in
.Fd \*[Lt]i386/segments.h\*[Gt] .
These structures are defined by the architecture
as disjoint bit-fields, so care must be taken in constructing them.
.Sh RETURN VALUES
Upon successful completion,
.Fn i386_get_ldt
returns the number of descriptors currently in the LDT.
.Fn i386_set_ldt
returns the first selector set.
Otherwise, a value of \-1 is returned and the global
variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn i386_get_ldt
and
.Fn i386_set_ldt
will fail if:
.Bl -tag -width [EINVAL]
.It Bq Er EINVAL
An inappropriate parameter was used for
.Fa start_sel
or
.Fa num_sels .
.It Bq Er EACCES
The caller attempted to use a descriptor that would
circumvent protection or cause a failure.
.El
.Sh REFERENCES
i386 Microprocessor Programmer's Reference Manual, Intel
.Sh WARNING
You can really hose your process using this.