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 #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. */
  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 }