1/* Copyright (C) 2001-2020 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_64 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 %%" RSP_LP ", %0" : "=r" (p__)); p__; })
38#define stackinfo_sub_sp(ptr) \
39 ({ ptrdiff_t d__; \
40 asm volatile ("sub %%" RSP_LP " , %0" : "=r" (d__) : "0" (ptr)); \
41 d__; })
42
43#endif /* stackinfo.h */
44