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

DEFINITIONS

1. check_host_supports_tls
2. os_set_thread_area
3. os_get_thread_area

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