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

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