1.\" Copyright (c) 2003,2004 The DragonFly Project. All rights reserved. 2.\" 3.\" This code is derived from software contributed to The DragonFly Project 4.\" by David Xu <davidxu@freebsd.org> and Matthew Dillon <dillon@backplane.com> 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in 14.\" the documentation and/or other materials provided with the 15.\" distribution. 16.\" 3. Neither the name of The DragonFly Project nor the names of its 17.\" contributors may be used to endorse or promote products derived 18.\" from this software without specific, prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25.\" INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.Dd February 21, 2005 34.Dt TLS 2 35.Os 36.Sh NAME 37.Nm set_tls_area , 38.Nm get_tls_area 39.Nd kernel TLS (thread local storage) support 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In sys/tls.h 44.Ft int 45.Fn set_tls_area "int which" "struct tls_info *info" "size_t infosize" 46.Ft int 47.Fn get_tls_area "int which" "struct tls_info *info" "size_t infosize" 48.Sh DESCRIPTION 49The 50.Fn set_tls_area 51system call creates an entry for the TLS facility 52.Fa which 53representing thread local storage as specified by the 54.Fa info 55structure. 56A descriptor representing the facility is returned, or -1 if an error occurred. 57The facility may be cleared by specifying a NULL pointer and an infosize of 0. 58The 59.Fn get_tls_area 60system call retrieves the requested TLS facility. 61A descriptor representing the facility is returned, or -1 if an error occurred. 62If you simply want the 63descriptor you may specify a NULL pointer and an infosize of 0. 64.Pp 65The returned descriptor and the TLS mechanism is machine-dependent. 66On IA32 67three global segment descriptors are supported (0, 1, and 2) and the %gs 68load value is returned. 69.Pp 70The 71.Fa tls_info 72structure passed to 73.Fn set_tls_area 74should first be zerod (to remain compatible with future extensions) 75and then initialized. 76.Bd -literal 77struct tls_info { 78 void *base; /* base address of TLS area */ 79 int size; /* size of TLS area in bytes */ 80}; 81.Ed 82.Pp 83The actual implementation of the area is machine-dependent. 84If the kernel 85is unable to accommodate the supplied size it may create a larger area. 86If the kernel is unable to accommodate the supplied base address an error 87will be returned. 88.Sh RETURN VALUES 89A return value of 0 is returned on success, -1 on error. 90.Sh EXAMPLES 91.Bd -literal -compact 92 93/* 94 * Pseudo example showing how the TLS system calls work on IA32. 95 */ 96#include <stdio.h> 97#include <unistd.h> 98#include <stdlib.h> 99#include <errno.h> 100#include <sys/tls.h> 101 102int X; 103 104static int getdata(int offset); 105 106int 107main(int ac, char **av) 108{ 109 int i; 110 int gs; 111 struct tls_info info; 112 113 info.base = &X; 114 info.size = sizeof(X); 115 if ((gs = set_tls_area(0, &info, sizeof(info))) < 0) { 116 perror("setarea"); 117 exit(1); 118 } 119 printf("gs = %04x\en", gs); 120 __asm __volatile("mov %0,%%gs" : : "g" (gs) ); 121 122 if (get_tls_area(0, &info, sizeof(info)) < 0) { 123 perror("getarea"); 124 exit(1); 125 } 126 printf("%p/%d\en", info.base, info.size); 127 128 X = 1; 129 printf("should be 1: %d\en", getdata(0)); 130 X = 2; 131 printf("should be 2: %d\en", getdata(0)); 132 133 printf("this should fault:\en"); 134 fflush(stdout); 135 getdata(4); 136 137 return(0); 138} 139 140static int 141getdata(int offset) 142{ 143 int rv; 144 __asm __volatile("movl %%gs:(%0),%%eax; movl %%eax,%1" : "+r" (offset) : "m" 145 (rv) : "ax"); 146 return (rv); 147} 148 149.Ed 150.Sh ERRORS 151.Bl -tag -width Er 152.It Bq Er ERANGE 153The specified facility index, 154.Fa which , 155is not supported. 156.It Bq Er EINVAL 157An invalid parameter has been specified. 158.It Bq Er ENOENT 159(get_tls_area) The specified facility has not been initialized with 160.Fn sys_set_tls_area . 161.El 162.Sh SEE ALSO 163.Xr umtx 2 164.Sh HISTORY 165The 166.Fn set_tls_area , 167and 168.Fn get_tls_area 169function calls first appeared in 170.Dx 1.1 . 171