arch/x86/um/os-Linux/tls.c

   1 #include <errno.h>
   2 #include <linux/unistd.h>
   3
   4 #include <sys/ptrace.h>
   5 #include <sys/syscall.h>
   6 #include <unistd.h>
   7
   8 #include "sysdep/tls.h"
   9
  10 #ifndef PTRACE_GET_THREAD_AREA
  11 #define PTRACE_GET_THREAD_AREA 25
  12 #endif
  13
  14 #ifndef PTRACE_SET_THREAD_AREA
  15 #define PTRACE_SET_THREAD_AREA 26
  16 #endif
  17
  18 /* Checks whether host supports TLS, and sets *tls_min according to the value
  19  * valid on the host.
  20  * i386 host have it == 6; x86_64 host have it == 12, for i386 emulation. */
  21 void check_host_supports_tls(int *supports_tls, int *tls_min)
  22 {
  23         /* Values for x86 and x86_64.*/
  24         int val[] = {GDT_ENTRY_TLS_MIN_I386, GDT_ENTRY_TLS_MIN_X86_64};
  25         int i;
  26
  27         for (i = 0; i < ARRAY_SIZE(val); i++) {
  28                 user_desc_t info;
  29                 info.entry_number = val[i];
  30
  31                 if (syscall(__NR_get_thread_area, &info) == 0) {
  32                         *tls_min = val[i];
  33                         *supports_tls = 1;
  34                         return;
  35                 } else {
  36                         if (errno == EINVAL)
  37                                 continue;
  38                         else if (errno == ENOSYS)
  39                                 *supports_tls = 0;
  40                                 return;
  41                 }
  42         }
  43
  44         *supports_tls = 0;
  45 }
  46
  47 int os_set_thread_area(user_desc_t *info, int pid)
  48 {
  49         int ret;
  50
  51         ret = ptrace(PTRACE_SET_THREAD_AREA, pid, info->entry_number,
  52                      (unsigned long) info);
  53         if (ret < 0)
  54                 ret = -errno;
  55         return ret;
  56 }
  57
  58 int os_get_thread_area(user_desc_t *info, int pid)
  59 {
  60         int ret;
  61
  62         ret = ptrace(PTRACE_GET_THREAD_AREA, pid, info->entry_number,
  63                      (unsigned long) info);
  64         if (ret < 0)
  65                 ret = -errno;
  66         return ret;
  67 }