1 #include <errno.h>
2 #include <linux/unistd.h>
3 
4 #include <sys/syscall.h>
5 #include <unistd.h>
6 
7 #include "sysdep/tls.h"
8 #include "user.h"
9 
10 /* Checks whether host supports TLS, and sets *tls_min according to the value
11  * valid on the host.
12  * i386 host have it == 6; x86_64 host have it == 12, for i386 emulation. */
check_host_supports_tls(int * supports_tls,int * tls_min)13 void check_host_supports_tls(int *supports_tls, int *tls_min) {
14 	/* Values for x86 and x86_64.*/
15 	int val[] = {GDT_ENTRY_TLS_MIN_I386, GDT_ENTRY_TLS_MIN_X86_64};
16 	int i;
17 
18 	for (i = 0; i < ARRAY_SIZE(val); i++) {
19 		user_desc_t info;
20 		info.entry_number = val[i];
21 
22 		if (syscall(__NR_get_thread_area, &info) == 0) {
23 			*tls_min = val[i];
24 			*supports_tls = 1;
25 			return;
26 		} else {
27 			if (errno == EINVAL)
28 				continue;
29 			else if (errno == ENOSYS)
30 				*supports_tls = 0;
31 				return;
32 		}
33 	}
34 
35 	*supports_tls = 0;
36 }
37