.\" Hey Emacs! This file is -*- nroff -*- source. .\" .\" Copyright (c) 1995 Michael Chastain (mec@duracef.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., 675 Mass Ave, Cambridge, MA 02139, .\" USA. .\" .TH MODIFY_LDT 2 "22 July 1995" "Linux 1.3.6" "Linux Programmer's Manual" .SH NAME modify_ldt \- get or set ldt .SH SYNOPSIS .nf .B #include .B #include .sp .B _syscall3( int, modify_ldt, int, func, void *, ptr, unsigned long, bytecount ) .sp .BI "int modify_ldt(int " "func" ", void *" "ptr" ", unsigned long " "bytecount" ");" .fi .SH DESCRIPTION .B 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. .PP When .I func is 0, .B modify_ldt reads the ldt into the memory pointed to by .IR ptr . The number of bytes read is the smaller of .I bytecount and the actual size of the ldt. .PP When .I func is 1, .B modify_ldt modifies one ldt entry. .I ptr points to a .I modify_ldt_ldt_s structure and .I bytecount must equal the size of this structure. .SH "RETURN VALUE" On success, .B modify_ldt returns either the actual number of bytes read (for reading) or 0 (for writing). On failure, .B modify_ldt returns \-1 and sets .IR errno . .SH ERRORS .TP .B ENOSYS .I func is neither 0 nor 1. .TP .B EINVAL .I ptr is 0, or .I func is 1 and .I bytecount is not equal to the size of the structure .IR modify_ldt_ldt_s , or .I func is 1 and the new ldt entry has illegal values. .TP .B EFAULT .I ptr points outside the address space. .SH "CONFORMING TO" This call in Linux-specfic and should not be used in programs intended to be portable. .SH "SEE ALSO" .BR vm86 (2)