arch/um/os-Linux/sys-i386/tls.c

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