sysdeps/i386/stackinfo.h

   1 /* Copyright (C) 1999-2022 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 /* This file contains a bit of information about the stack allocation
  19    of the processor.  */
  20
  21 #ifndef _STACKINFO_H
  22 #define _STACKINFO_H    1
  23
  24 #include <elf.h>
  25
  26 /* On x86 the stack grows down.  */
  27 #define _STACK_GROWS_DOWN       1
  28
  29 /* Default to an executable stack.  PF_X can be overridden if PT_GNU_STACK is
  30  * present, but it is presumed absent.  */
  31 #define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
  32
  33 /* Access to the stack pointer.  The macros are used in alloca_account
  34    for which they need to act as barriers as well, hence the additional
  35    (unnecessary) parameters.  */
  36 #define stackinfo_get_sp() \
  37   ({ void *p__; asm volatile ("mov %%esp, %0" : "=r" (p__)); p__; })
  38 #define stackinfo_sub_sp(ptr) \
  39   ({ ptrdiff_t d__;                                             \
  40      asm volatile ("sub %%esp, %0" : "=r" (d__) : "0" (ptr));   \
  41      d__; })
  42
  43 #endif  /* stackinfo.h */