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33 .\" $DragonFly: src/lib/libc/sys/tls.2,v 1.11 2008/05/02 02:05:04 swildner Exp $
41 .Nd kernel TLS (thread local storage) support.
47 .Fn set_tls_area "int which" "struct tls_info *info" "size_t infosize"
49 .Fn 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 occurred. 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 occurred. 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-dependent. 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)
78 void *base; /* base address of TLS area */
79 int size; /* size of TLS area in bytes */
83 The actual implementation of the area is machine-dependent. If the kernel
84 is unable to accommodate the supplied size it may create a larger area.
85 If the kernel is unable to accommodate the supplied base address an error
88 A return value of 0 is returned on success, -1 on error.
93 * Pseudo example showing how the TLS system calls work on IA32.
103 static int getdata(int offset);
106 main(int ac, char **av)
110 struct tls_info info;
113 info.size = sizeof(X);
114 if ((gs = set_tls_area(0, &info, sizeof(info))) < 0) {
118 printf("gs = %04x\en", gs);
119 __asm __volatile("mov %0,%%gs" : : "g" (gs) );
121 if (get_tls_area(0, &info, sizeof(info)) < 0) {
125 printf("%p/%d\en", info.base, info.size);
128 printf("should be 1: %d\en", getdata(0));
130 printf("should be 2: %d\en", getdata(0));
132 printf("this should fault:\en");
143 __asm __volatile("movl %%gs:(%0),%%eax; movl %%eax,%1" : "+r" (offset) : "m"
152 The specified facility index,
156 An invalid parameter has been specified.
158 (get_tls_area) The specified facility has not been initialized with
159 .Fn sys_set_tls_area .
168 function calls first appeared in