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

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <errno.h>
   3 #include <linux/unistd.h>
   4
   5 #include <sys/ptrace.h>
   6 #include <sys/syscall.h>
   7 #include <unistd.h>
   8
   9 #include <os.h>
  10 #include <sysdep/tls.h>
  11
  12 #ifndef PTRACE_GET_THREAD_AREA
  13 #define PTRACE_GET_THREAD_AREA 25
  14 #endif
  15
  16 #ifndef PTRACE_SET_THREAD_AREA
  17 #define PTRACE_SET_THREAD_AREA 26
  18 #endif
  19
  20 /* Checks whether host supports TLS, and sets *tls_min according to the value
  21  * valid on the host.
  22  * i386 host have it == 6; x86_64 host have it == 12, for i386 emulation. */
  23 void check_host_supports_tls(int *supports_tls, int *tls_min)
  24 {
  25         /* Values for x86 and x86_64.*/
  26         int val[] = {GDT_ENTRY_TLS_MIN_I386, GDT_ENTRY_TLS_MIN_X86_64};
  27         int i;
  28
  29         for (i = 0; i < ARRAY_SIZE(val); i++) {
  30                 user_desc_t info;
  31                 info.entry_number = val[i];
  32
  33                 if (syscall(__NR_get_thread_area, &info) == 0) {
  34                         *tls_min = val[i];
  35                         *supports_tls = 1;
  36                         return;
  37                 } else {
  38                         if (errno == EINVAL)
  39                                 continue;
  40                         else if (errno == ENOSYS)
  41                                 *supports_tls = 0;
  42                         return;
  43                 }
  44         }
  45
  46         *supports_tls = 0;
  47 }
  48
  49 int os_set_thread_area(user_desc_t *info, int pid)
  50 {
  51         int ret;
  52
  53         ret = ptrace(PTRACE_SET_THREAD_AREA, pid, info->entry_number,
  54                      (unsigned long) info);
  55         if (ret < 0)
  56                 ret = -errno;
  57         return ret;
  58 }
  59
  60 int os_get_thread_area(user_desc_t *info, int pid)
  61 {
  62         int ret;
  63
  64         ret = ptrace(PTRACE_GET_THREAD_AREA, pid, info->entry_number,
  65                      (unsigned long) info);
  66         if (ret < 0)
  67                 ret = -errno;
  68         return ret;
  69 }