1  /* Pointer guard implementation.  Alpha version.
       2     Copyright (C) 2006-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library.  If not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #ifndef POINTER_GUARD_H
      20  #define POINTER_GUARD_H
      21  
      22  /* Pointer mangling support.  Note that tls access is slow enough that
      23     we don't deoptimize things by placing the pointer check value there.  */
      24  
      25  #ifdef __ASSEMBLER__
      26  # if IS_IN (rtld)
      27  #  define PTR_MANGLE(dst, src, tmp)                             \
      28          ldah    tmp, __pointer_chk_guard_local($29) !gprelhigh; \
      29          ldq     tmp, __pointer_chk_guard_local(tmp) !gprellow;  \
      30          xor     src, tmp, dst
      31  #  define PTR_MANGLE2(dst, src, tmp)                            \
      32          xor     src, tmp, dst
      33  # elif defined SHARED
      34  #  define PTR_MANGLE(dst, src, tmp)             \
      35          ldq     tmp, __pointer_chk_guard;       \
      36          xor     src, tmp, dst
      37  # else
      38  #  define PTR_MANGLE(dst, src, tmp)             \
      39          ldq     tmp, __pointer_chk_guard_local; \
      40          xor     src, tmp, dst
      41  # endif
      42  # define PTR_MANGLE2(dst, src, tmp)             \
      43          xor     src, tmp, dst
      44  # define PTR_DEMANGLE(dst, tmp)   PTR_MANGLE(dst, dst, tmp)
      45  # define PTR_DEMANGLE2(dst, tmp)  PTR_MANGLE2(dst, dst, tmp)
      46  #else
      47  # include <stdint.h>
      48  # if (IS_IN (rtld) \
      49        || (!defined SHARED && (IS_IN (libc) \
      50                                || IS_IN (libpthread))))
      51  extern uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
      52  #  define PTR_MANGLE(var) \
      53          (var) = (__typeof (var)) ((uintptr_t) (var) ^ __pointer_chk_guard_local)
      54  # else
      55  extern uintptr_t __pointer_chk_guard attribute_relro;
      56  #  define PTR_MANGLE(var) \
      57          (var) = (__typeof(var)) ((uintptr_t) (var) ^ __pointer_chk_guard)
      58  # endif
      59  # define PTR_DEMANGLE(var)  PTR_MANGLE(var)
      60  #endif /* ASSEMBLER */
      61  
      62  #endif /* POINTER_GUARD_H */