Blame sysdeps/x86_64/stackinfo.h

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/* Copyright (C) 2001-2018 Free Software Foundation, Inc.
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   This file is part of the GNU C Library.
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   The GNU C Library is free software; you can redistribute it and/or
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   modify it under the terms of the GNU Lesser General Public
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   License as published by the Free Software Foundation; either
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   version 2.1 of the License, or (at your option) any later version.
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   The GNU C Library is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   Lesser General Public License for more details.
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   You should have received a copy of the GNU Lesser General Public
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   License along with the GNU C Library; if not, see
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   <http://www.gnu.org/licenses/>.  */
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/* This file contains a bit of information about the stack allocation
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   of the processor.  */
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#ifndef _STACKINFO_H
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#define _STACKINFO_H	1
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#include <elf.h>
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/* On x86_64 the stack grows down.  */
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#define _STACK_GROWS_DOWN	1
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/* Default to an executable stack.  PF_X can be overridden if PT_GNU_STACK is
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 * present, but it is presumed absent.  */
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#define DEFAULT_STACK_PERMS (PF_R|PF_W|PF_X)
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/* Access to the stack pointer.  The macros are used in alloca_account
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   for which they need to act as barriers as well, hence the additional
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   (unnecessary) parameters.  */
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#define stackinfo_get_sp() \
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  ({ void *p__; asm volatile ("mov %%" RSP_LP ", %0" : "=r" (p__)); p__; })
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#define stackinfo_sub_sp(ptr) \
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  ({ ptrdiff_t d__;						\
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     asm volatile ("sub %%" RSP_LP " , %0" : "=r" (d__) : "0" (ptr));	\
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     d__; })
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#endif	/* stackinfo.h */