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.\" $DragonFly: src/lib/libc/sys/tls.2,v 1.4 2005/03/21 17:11:38 joerg Exp $ 34.\" 35.Dd February 21, 2005 36.Dt TLS 2 37.Os 38.Sh NAME 39.Nm sys_set_tls_area , 40.Nm sys_get_tls_area 41.Nd kernel TLS (thread local storage) support. 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/tls.h 46.Ft int 47.Fn sys_set_tls_area "int which" "struct tls_info *info" "size_t infosize" 48.Ft int 49.Fn sys_get_tls_area "int which" "struct tls_info *info" "size_t infosize" 50.Sh DESCRIPTION 51The 52.Fn sys_set_tls_area 53system call creates an entry for the TLS facility 54.Fa which 55representing thread local storage as specified by the 56.Fa info 57structure. A descriptor representing the facility is returned, or -1 if 58an error occured. The facility may be cleared by specifying a NULL pointer 59and an infosize of 0. 60The 61.Fn sys_get_tls_area 62system call retrieves the requested TLS facility. A descriptor representing 63the facility is returned, or -1 if an error occured. If you simply want the 64descriptor you may specify a NULL pointer and an infosize of 0. 65.Pp 66The returned descriptor and the TLS mechanism is machine-dependant. On 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 sys_set_tls_area 74should first be zerod (to remain compatible with future extensions) 75and then initialized. 76.Pp 77.Bd -literal 78struct tls_info { 79 void *base; /* base address of TLS area */ 80 int size; /* size of TLS area in bytes */ 81}; 82.Ed 83.Pp 84The actual implementation of the area is machine-dependant. If the kernel 85is unable to accomodate the supplied size it may create a larger area. 86If the kernel is unable to accomodate 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 ERRORS 91.Bl -tag -width Er 92.It Bq Er ERANGE 93The specified facility index, 94.Fa which , 95is not supported. 96.It Bq Er EINVAL 97An invalid parameter has been specified. 98.It Bq Er ENOENT 99(sys_get_tls_area) The specified facility has not been initialized with 100.Fn sys_set_tls_area . 101.El 102.Sh EXAMPLE 103.Bd -literal -compact 104 105/* 106 * Pseudo example showing how the TLS system calls work on IA32. 107 */ 108#include <stdio.h> 109#include <unistd.h> 110#include <stdlib.h> 111#include <errno.h> 112#include <sys/tls.h> 113 114int X; 115 116static int getdata(int offset); 117 118int 119main(int ac, char **av) 120{ 121 int i; 122 int gs; 123 struct tls_info info; 124 125 info.base = &X; 126 info.size = sizeof(X); 127 if ((gs = sys_set_tls_area(0, &info, sizeof(info))) < 0) { 128 perror("setarea"); 129 exit(1); 130 } 131 printf("gs = %04x\n", gs); 132 __asm __volatile("movl %0,%%eax; movl %%eax,%%gs" : "=m" (gs) : : "ax"); 133 134 if (sys_get_tls_area(0, &info, sizeof(info)) < 0) { 135 perror("getarea"); 136 exit(1); 137 } 138 printf("%p/%d\n", info.base, info.size); 139 140 X = 1; 141 printf("should be 1: %d\n", getdata(0)); 142 X = 2; 143 printf("should be 2: %d\n", getdata(0)); 144 145 printf("this should fault:\n"); 146 fflush(stdout); 147 getdata(4); 148 149 return(0); 150} 151 152static int 153getdata(int offset) 154{ 155 int rv; 156 __asm __volatile("movl %%gs:(%0),%%eax; movl %%eax,%1" : "+r" (offset) : "m" 157 (rv) : "ax"); 158 return (rv); 159} 160 161.Ed 162.Sh SEE ALSO 163.Xr umtx 2 164.Sh HISTORY 165The 166.Fn sys_set_tls_area , 167and 168.Fn sys_get_tls_area 169function calls first appeared in DragonFly 1.1 . 170