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93 lines
2.6 KiB
C
93 lines
2.6 KiB
C
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/* Implement __enable_execute_stack using mprotect(2).
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Copyright (C) 2011, 2012 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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#include <sys/mman.h>
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#include <unistd.h>
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#include <stdlib.h>
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#define STACK_PROT_RWX (PROT_READ | PROT_WRITE | PROT_EXEC)
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static int need_enable_exec_stack;
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static void check_enabling (void) __attribute__ ((unused));
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extern void __enable_execute_stack (void *);
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#if defined __FreeBSD__
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#include <sys/sysctl.h>
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static void __attribute__ ((constructor))
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check_enabling (void)
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{
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int prot = 0;
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size_t len = sizeof (prot);
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sysctlbyname ("kern.stackprot", &prot, &len, NULL, 0);
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if (prot != STACK_PROT_RWX)
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need_enable_exec_stack = 1;
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}
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#elif defined __sun__ && defined __svr4__
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static void __attribute__ ((constructor))
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check_enabling (void)
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{
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int prot = (int) sysconf (_SC_STACK_PROT);
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if (prot != STACK_PROT_RWX)
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need_enable_exec_stack = 1;
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}
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#else
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/* There is no way to query the execute permission of the stack, so
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we always issue the mprotect() call. */
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static int need_enable_exec_stack = 1;
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#endif
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/* Attempt to turn on access permissions for the stack. Unfortunately it
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is not possible to make this namespace-clean.*/
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void
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__enable_execute_stack (void *addr)
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{
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if (!need_enable_exec_stack)
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return;
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else
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{
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static long size, mask;
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if (size == 0) {
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size = getpagesize ();
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mask = ~(size - 1);
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}
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char *page = (char *) (((long) addr) & mask);
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char *end = (char *)
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((((long) (addr + __LIBGCC_TRAMPOLINE_SIZE__)) & mask) + size);
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if (mprotect (page, end - page, STACK_PROT_RWX) < 0)
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/* Note that no errors should be emitted by this code; it is
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considered dangerous for library calls to send messages to
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stdout/stderr. */
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abort ();
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}
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}
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