1  /* Out-of-line LSE atomics for AArch64 architecture, Init.
       2     Copyright (C) 2019-2023 Free Software Foundation, Inc.
       3     Contributed by Linaro Ltd.
       4  
       5  This file is part of GCC.
       6  
       7  GCC is free software; you can redistribute it and/or modify it under
       8  the terms of the GNU General Public License as published by the Free
       9  Software Foundation; either version 3, or (at your option) any later
      10  version.
      11  
      12  GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      13  WARRANTY; without even the implied warranty of MERCHANTABILITY or
      14  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      15  for more details.
      16  
      17  Under Section 7 of GPL version 3, you are granted additional
      18  permissions described in the GCC Runtime Library Exception, version
      19  3.1, as published by the Free Software Foundation.
      20  
      21  You should have received a copy of the GNU General Public License and
      22  a copy of the GCC Runtime Library Exception along with this program;
      23  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      24  <http://www.gnu.org/licenses/>.  */
      25  
      26  #include "auto-target.h"
      27  
      28  /* Define the symbol gating the LSE implementations.  */
      29  _Bool __aarch64_have_lse_atomics
      30    __attribute__((visibility("hidden"), nocommon));
      31  
      32  /* Gate availability of __getauxval on glibc.  All AArch64-supporting glibc
      33     versions support it.  */
      34  #ifdef __gnu_linux__
      35  
      36  # define AT_HWCAP	16
      37  # define HWCAP_ATOMICS	(1 << 8)
      38  
      39  unsigned long int __getauxval (unsigned long int);
      40  
      41  /* Use a higher priority to ensure it runs before user constructors
      42     and library constructors with priority 100. */
      43  static void __attribute__((constructor (90)))
      44  init_have_lse_atomics (void)
      45  {
      46    unsigned long hwcap = __getauxval (AT_HWCAP);
      47    __aarch64_have_lse_atomics = (hwcap & HWCAP_ATOMICS) != 0;
      48  }
      49  
      50  #endif /* __gnu_linux__  */