1 .\" Copyright (c) 2003,2004 The DragonFly Project. All rights reserved.
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>
6 .\" Redistribution and use in source and binary forms, with or without
7 .\" modification, are permitted provided that the following conditions
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
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.
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
33 .\" $DragonFly: src/lib/libc/sys/tls.2,v 1.4 2005/03/21 17:11:38 joerg Exp $
39 .Nm sys_set_tls_area ,
41 .Nd kernel TLS (thread local storage) support.
47 .Fn sys_set_tls_area "int which" "struct tls_info *info" "size_t infosize"
49 .Fn sys_get_tls_area "int which" "struct tls_info *info" "size_t infosize"
53 system call creates an entry for the TLS facility
55 representing thread local storage as specified by the
57 structure. A descriptor representing the facility is returned, or -1 if
58 an error occured. The facility may be cleared by specifying a NULL pointer
62 system call retrieves the requested TLS facility. A descriptor representing
63 the facility is returned, or -1 if an error occured. If you simply want the
64 descriptor you may specify a NULL pointer and an infosize of 0.
66 The returned descriptor and the TLS mechanism is machine-dependant. On IA32
67 three global segment descriptors are supported (0, 1, and 2) and the %gs
68 load value is returned.
74 should first be zerod (to remain compatible with future extensions)
79 void *base; /* base address of TLS area */
80 int size; /* size of TLS area in bytes */
84 The actual implementation of the area is machine-dependant. If the kernel
85 is unable to accomodate the supplied size it may create a larger area.
86 If the kernel is unable to accomodate the supplied base address an error
89 A return value of 0 is returned on success, -1 on error.
93 The specified facility index,
97 An invalid parameter has been specified.
99 (sys_get_tls_area) The specified facility has not been initialized with
100 .Fn sys_set_tls_area .
103 .Bd -literal -compact
106 * Pseudo example showing how the TLS system calls work on IA32.
116 static int getdata(int offset);
119 main(int ac, char **av)
123 struct tls_info info;
126 info.size = sizeof(X);
127 if ((gs = sys_set_tls_area(0, &info, sizeof(info))) < 0) {
131 printf("gs = %04x\n", gs);
132 __asm __volatile("movl %0,%%eax; movl %%eax,%%gs" : "=m" (gs) : : "ax");
134 if (sys_get_tls_area(0, &info, sizeof(info)) < 0) {
138 printf("%p/%d\n", info.base, info.size);
141 printf("should be 1: %d\n", getdata(0));
143 printf("should be 2: %d\n", getdata(0));
145 printf("this should fault:\n");
156 __asm __volatile("movl %%gs:(%0),%%eax; movl %%eax,%1" : "+r" (offset) : "m"
166 .Fn sys_set_tls_area ,
169 function calls first appeared in DragonFly 1.1 .