148fb7bfaSmrg /* Implement __enable_execute_stack using mprotect(2).
2*b1e83836Smrg Copyright (C) 2011-2022 Free Software Foundation, Inc.
348fb7bfaSmrg
448fb7bfaSmrg This file is part of GCC.
548fb7bfaSmrg
648fb7bfaSmrg GCC is free software; you can redistribute it and/or modify it under
748fb7bfaSmrg the terms of the GNU General Public License as published by the Free
848fb7bfaSmrg Software Foundation; either version 3, or (at your option) any later
948fb7bfaSmrg version.
1048fb7bfaSmrg
1148fb7bfaSmrg GCC is distributed in the hope that it will be useful, but WITHOUT ANY
1248fb7bfaSmrg WARRANTY; without even the implied warranty of MERCHANTABILITY or
1348fb7bfaSmrg FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1448fb7bfaSmrg for more details.
1548fb7bfaSmrg
1648fb7bfaSmrg Under Section 7 of GPL version 3, you are granted additional
1748fb7bfaSmrg permissions described in the GCC Runtime Library Exception, version
1848fb7bfaSmrg 3.1, as published by the Free Software Foundation.
1948fb7bfaSmrg
2048fb7bfaSmrg You should have received a copy of the GNU General Public License and
2148fb7bfaSmrg a copy of the GCC Runtime Library Exception along with this program;
2248fb7bfaSmrg see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
2348fb7bfaSmrg <http://www.gnu.org/licenses/>. */
2448fb7bfaSmrg
2548fb7bfaSmrg #include <sys/mman.h>
2648fb7bfaSmrg #include <unistd.h>
2748fb7bfaSmrg #include <stdlib.h>
2848fb7bfaSmrg
2948fb7bfaSmrg #define STACK_PROT_RWX (PROT_READ | PROT_WRITE | PROT_EXEC)
3048fb7bfaSmrg
3148fb7bfaSmrg static int need_enable_exec_stack;
3248fb7bfaSmrg
3348fb7bfaSmrg static void check_enabling (void) __attribute__ ((unused));
3448fb7bfaSmrg extern void __enable_execute_stack (void *);
3548fb7bfaSmrg
364d5abbe8Smrg #if defined __sun__ && defined __svr4__
3748fb7bfaSmrg static void __attribute__ ((constructor))
check_enabling(void)3848fb7bfaSmrg check_enabling (void)
3948fb7bfaSmrg {
4048fb7bfaSmrg int prot = (int) sysconf (_SC_STACK_PROT);
4148fb7bfaSmrg
4248fb7bfaSmrg if (prot != STACK_PROT_RWX)
4348fb7bfaSmrg need_enable_exec_stack = 1;
4448fb7bfaSmrg }
4548fb7bfaSmrg #else
4648fb7bfaSmrg /* There is no way to query the execute permission of the stack, so
4748fb7bfaSmrg we always issue the mprotect() call. */
4848fb7bfaSmrg
4948fb7bfaSmrg static int need_enable_exec_stack = 1;
5048fb7bfaSmrg #endif
5148fb7bfaSmrg
5248fb7bfaSmrg /* Attempt to turn on access permissions for the stack. Unfortunately it
5348fb7bfaSmrg is not possible to make this namespace-clean.*/
5448fb7bfaSmrg
5548fb7bfaSmrg void
__enable_execute_stack(void * addr)5648fb7bfaSmrg __enable_execute_stack (void *addr)
5748fb7bfaSmrg {
5848fb7bfaSmrg if (!need_enable_exec_stack)
5948fb7bfaSmrg return;
6048fb7bfaSmrg else
6148fb7bfaSmrg {
6248fb7bfaSmrg static long size, mask;
6348fb7bfaSmrg
6448fb7bfaSmrg if (size == 0) {
6548fb7bfaSmrg size = getpagesize ();
6648fb7bfaSmrg mask = ~(size - 1);
6748fb7bfaSmrg }
6848fb7bfaSmrg
6948fb7bfaSmrg char *page = (char *) (((long) addr) & mask);
7048fb7bfaSmrg char *end = (char *)
7148fb7bfaSmrg ((((long) (addr + __LIBGCC_TRAMPOLINE_SIZE__)) & mask) + size);
7248fb7bfaSmrg
7348fb7bfaSmrg if (mprotect (page, end - page, STACK_PROT_RWX) < 0)
7448fb7bfaSmrg /* Note that no errors should be emitted by this code; it is
7548fb7bfaSmrg considered dangerous for library calls to send messages to
7648fb7bfaSmrg stdout/stderr. */
7748fb7bfaSmrg abort ();
7848fb7bfaSmrg }
7948fb7bfaSmrg }
80