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

   1 #include <errno.h>
   2 #include <linux/unistd.h>
   3 #include "sysdep/tls.h"
   4 #include "user_util.h"
   5
   6 static _syscall1(int, get_thread_area, user_desc_t *, u_info);
   7
   8 /* Checks whether host supports TLS, and sets *tls_min according to the value
   9  * valid on the host.
  10  * i386 host have it == 6; x86_64 host have it == 12, for i386 emulation. */
  11 void check_host_supports_tls(int *supports_tls, int *tls_min) {
  12         /* Values for x86 and x86_64.*/
  13         int val[] = {GDT_ENTRY_TLS_MIN_I386, GDT_ENTRY_TLS_MIN_X86_64};
  14         int i;
  15
  16         for (i = 0; i < ARRAY_SIZE(val); i++) {
  17                 user_desc_t info;
  18                 info.entry_number = val[i];
  19
  20                 if (get_thread_area(&info) == 0) {
  21                         *tls_min = val[i];
  22                         *supports_tls = 1;
  23                         return;
  24                 } else {
  25                         if (errno == EINVAL)
  26                                 continue;
  27                         else if (errno == ENOSYS)
  28                                 *supports_tls = 0;
  29                                 return;
  30                 }
  31         }
  32
  33         *supports_tls = 0;
  34 }