sysdeps/unix/sysv/linux/i386/pointer_guard.h

   1 /* Pointer obfuscation implenentation.  i386 version.
   2    Copyright (C) 2005-2023 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 #include <tcb-offsets.h>
  23
  24 #if IS_IN (rtld)
  25 /* We cannot use the thread descriptor because in ld.so we use setjmp
  26    earlier than the descriptor is initialized.  Using a global variable
  27    is too complicated here since we have no PC-relative addressing mode.  */
  28 # include <sysdeps/generic/pointer_guard.h>
  29 #else
  30 # ifdef __ASSEMBLER__
  31 #  define PTR_MANGLE(reg)       xorl %gs:POINTER_GUARD, reg;                  \
  32                                 roll $9, reg
  33 #  define PTR_DEMANGLE(reg)     rorl $9, reg;                                 \
  34                                 xorl %gs:POINTER_GUARD, reg
  35 # else
  36 #  define PTR_MANGLE(var)       asm ("xorl %%gs:%c2, %0\n"                    \
  37                                      "roll $9, %0"                            \
  38                                      : "=r" (var)                             \
  39                                      : "0" (var),                             \
  40                                        "i" (POINTER_GUARD))
  41 #  define PTR_DEMANGLE(var)     asm ("rorl $9, %0\n"                          \
  42                                      "xorl %%gs:%c2, %0"                      \
  43                                      : "=r" (var)                             \
  44                                      : "0" (var),                             \
  45                                        "i" (POINTER_GUARD))
  46 # endif
  47 #endif
  48
  49 #endif /* POINTER_GUARD_H */