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- /* Implement __enable_execute_stack using mprotect(2).
- Copyright (C) 2011-2022 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
- version.
- 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
- <http://www.gnu.org/licenses/>. */
- #include <sys/mman.h>
- #include <unistd.h>
- #include <stdlib.h>
- #define STACK_PROT_RWX (PROT_READ | PROT_WRITE | PROT_EXEC)
- 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;
- }
- #else
- /* 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;
- #endif
- /* Attempt to turn on access permissions for the stack. Unfortunately it
- is not possible to make this namespace-clean.*/
- void
- __enable_execute_stack (void *addr)
- {
- if (!need_enable_exec_stack)
- return;
- else
- {
- 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 ();
- }
- }
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