Add missing .El to silence groff warning.
[dragonfly.git] / lib / libc / sys / tls.2
CommitLineData
806bf111
MD
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.\"
720180cd 33.\" $DragonFly: src/lib/libc/sys/tls.2,v 1.2 2005/02/23 21:54:01 swildner Exp $
806bf111
MD
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" "int infosize"
48.Ft int
49.Fn sys_get_tls_area "int which" "struct tls_info *info" "int 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
89.Sh RETURN VALUES
90A return value of 0 is returned on success, -1 on error.
91.Sh ERRORS
92.Bl -tag -width Er
93.It Bq Er ERANGE
94The specified facility index,
95.Fa which ,
96is not supported.
97.It Bq Er EINVAL
98An invalid parameter has been specified.
99.It Bq Er ENOENT
100(sys_get_tls_area) The specified facility has not been initialized with
101.Fn sys_set_tls_area .
720180cd 102.El
806bf111
MD
103.Sh EXAMPLE
104.Bd -literal -compact
105
106/*
107 * Pseudo example showing how the TLS system calls work on IA32.
108 */
109#include <stdio.h>
110#include <unistd.h>
111#include <stdlib.h>
112#include <errno.h>
113#include <sys/tls.h>
114
115int X;
116
117static int getdata(int offset);
118
119int
120main(int ac, char **av)
121{
122 int i;
123 int gs;
124 struct tls_info info;
125
126 info.base = &X;
127 info.size = sizeof(X);
128 if ((gs = sys_set_tls_area(0, &info, sizeof(info))) < 0) {
129 perror("setarea");
130 exit(1);
131 }
132 printf("gs = %04x\n", gs);
133 __asm __volatile("movl %0,%%eax; movl %%eax,%%gs" : "=m" (gs) : : "ax");
134
135 if (sys_get_tls_area(0, &info, sizeof(info)) < 0) {
136 perror("getarea");
137 exit(1);
138 }
139 printf("%p/%d\n", info.base, info.size);
140
141 X = 1;
142 printf("should be 1: %d\n", getdata(0));
143 X = 2;
144 printf("should be 2: %d\n", getdata(0));
145
146 printf("this should fault:\n");
147 fflush(stdout);
148 getdata(4);
149
150 return(0);
151}
152
153static int
154getdata(int offset)
155{
156 int rv;
157 __asm __volatile("movl %%gs:(%0),%%eax; movl %%eax,%1" : "+r" (offset) : "m"
158 (rv) : "ax");
159 return (rv);
160}
161
162.Ed
163
164.Sh SEE ALSO
165.Xr umtx 2
166.Sh HISTORY
167The
168.Fn sys_set_tls_area ,
169and
170.Fn sys_get_tls_area
171function calls first appeared in DragonFly 1.1 .