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/* Implement __enable_execute_stack using mprotect(2). |
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Copyright (C) 2011-2015 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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. */ |
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#include |
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#include |
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#include |
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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 __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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} |