modify_ldt — get or set ldt
#include <sys/types.h>
int
modify_ldt( |
int | func, |
| void * | ptr, | |
| unsigned long | bytecount); |
modify_ldt() reads or writes
the local descriptor table (ldt) for a process. The ldt is a
per-process memory management table used by the i386
processor. For more information on this table, see an Intel
386 processor handbook.
When func is 0,
modify_ldt() reads the ldt into
the memory pointed to by ptr. The number of bytes read
is the smaller of bytecount and the actual size
of the ldt.
When func is 1,
modify_ldt() modifies one ldt
entry. ptr points to
a user_desc
structure and bytecount must equal the size
of this structure.
The user_desc
structure is defined in <asm/ldt.h>
as:
struct user_desc { unsigned int entry_number;unsigned long base_addr;unsigned int limit;unsigned int seg_32bit:1;unsigned int contents:2;unsigned int read_exec_only:1;unsigned int limit_in_pages:1;unsigned int seg_not_present:1;unsigned int useable:1;};
In Linux 2.4 and earlier, this structure was named
modify_ldt_ldt_s.
On success, modify_ldt()
returns either the actual number of bytes read (for reading)
or 0 (for writing). On failure, modify_ldt() returns −1 and sets
errno to indicate the error.
ptr points
outside the address space.
ptr is 0, or
func is 1 and
bytecount is
not equal to the size of the structure modify_ldt_ldt_s, or
func is 1 and
the new ldt entry has invalid values.
func is
neither 0 nor 1.
This call is Linux-specific and should not be used in programs intended to be portable.
This page is part of release 2.79 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
|
Copyright (c) 1995 Michael Chastain (mecduracef.shout.net), 22 July 1995. This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU General Public License's references to "object code" and "executables" are to be interpreted as the output of any document formatting or typesetting system, including intermediate and printed output. This manual is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this manual; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA. |