view libgcc/enable-execute-stack-mprotect.c @ 158:494b0b89df80 default tip

author Shinji KONO <>
date Mon, 25 May 2020 18:13:55 +0900
parents 1830386684a0
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/* Implement __enable_execute_stack using mprotect(2).
   Copyright (C) 2011-2020 Free Software Foundation, Inc.

   This file is part of GCC.

   GCC is free software; you can redistribute it and/or modify it under
   the terms of the GNU General Public License as published by the Free
   Software Foundation; either version 3, or (at your option) any later

   GCC is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or
   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   for more details.

   Under Section 7 of GPL version 3, you are granted additional
   permissions described in the GCC Runtime Library Exception, version
   3.1, as published by the Free Software Foundation.

   You should have received a copy of the GNU General Public License and
   a copy of the GCC Runtime Library Exception along with this program;
   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
   <>.  */

#include <sys/mman.h>
#include <unistd.h>
#include <stdlib.h>


static int need_enable_exec_stack;

static void check_enabling (void) __attribute__ ((unused));
extern void __enable_execute_stack (void *);

#if defined __sun__ && defined __svr4__
static void __attribute__ ((constructor))
check_enabling (void)
  int prot = (int) sysconf (_SC_STACK_PROT);

  if (prot != STACK_PROT_RWX)
    need_enable_exec_stack = 1;
/* There is no way to query the execute permission of the stack, so
   we always issue the mprotect() call.  */

static int need_enable_exec_stack = 1;

/* Attempt to turn on access permissions for the stack.  Unfortunately it
   is not possible to make this namespace-clean.*/

__enable_execute_stack (void *addr)
  if (!need_enable_exec_stack)
      static long size, mask;

      if (size == 0) {
	size = getpagesize ();
	mask = ~(size - 1);

      char *page = (char *) (((long) addr) & mask);
      char *end  = (char *)
	((((long) (addr + __LIBGCC_TRAMPOLINE_SIZE__)) & mask) + size);

      if (mprotect (page, end - page, STACK_PROT_RWX) < 0)
	/* Note that no errors should be emitted by this code; it is
	   considered dangerous for library calls to send messages to
	   stdout/stderr.  */
	abort ();