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10e48e39 | 1 | /* Implement __enable_execute_stack using mprotect(2). |
a5544970 | 2 | Copyright (C) 2011-2019 Free Software Foundation, Inc. |
10e48e39 RO |
3 | |
4 | This file is part of GCC. | |
5 | ||
6 | GCC is free software; you can redistribute it and/or modify it under | |
7 | the terms of the GNU General Public License as published by the Free | |
8 | Software Foundation; either version 3, or (at your option) any later | |
9 | version. | |
10 | ||
11 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
12 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
13 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
14 | for more details. | |
15 | ||
16 | Under Section 7 of GPL version 3, you are granted additional | |
17 | permissions described in the GCC Runtime Library Exception, version | |
18 | 3.1, as published by the Free Software Foundation. | |
19 | ||
20 | You should have received a copy of the GNU General Public License and | |
21 | a copy of the GCC Runtime Library Exception along with this program; | |
22 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
23 | <http://www.gnu.org/licenses/>. */ | |
24 | ||
25 | #include <sys/mman.h> | |
26 | #include <unistd.h> | |
27 | #include <stdlib.h> | |
28 | ||
29 | #define STACK_PROT_RWX (PROT_READ | PROT_WRITE | PROT_EXEC) | |
30 | ||
31 | static int need_enable_exec_stack; | |
32 | ||
33 | static void check_enabling (void) __attribute__ ((unused)); | |
34 | extern void __enable_execute_stack (void *); | |
35 | ||
dbed5a9b | 36 | #if defined __sun__ && defined __svr4__ |
10e48e39 RO |
37 | static void __attribute__ ((constructor)) |
38 | check_enabling (void) | |
39 | { | |
40 | int prot = (int) sysconf (_SC_STACK_PROT); | |
41 | ||
42 | if (prot != STACK_PROT_RWX) | |
43 | need_enable_exec_stack = 1; | |
44 | } | |
45 | #else | |
46 | /* There is no way to query the execute permission of the stack, so | |
47 | we always issue the mprotect() call. */ | |
48 | ||
49 | static int need_enable_exec_stack = 1; | |
50 | #endif | |
51 | ||
10e48e39 RO |
52 | /* Attempt to turn on access permissions for the stack. Unfortunately it |
53 | is not possible to make this namespace-clean.*/ | |
54 | ||
55 | void | |
56 | __enable_execute_stack (void *addr) | |
57 | { | |
58 | if (!need_enable_exec_stack) | |
59 | return; | |
60 | else | |
61 | { | |
62 | static long size, mask; | |
63 | ||
64 | if (size == 0) { | |
65 | size = getpagesize (); | |
66 | mask = ~(size - 1); | |
67 | } | |
68 | ||
69 | char *page = (char *) (((long) addr) & mask); | |
70 | char *end = (char *) | |
71 | ((((long) (addr + __LIBGCC_TRAMPOLINE_SIZE__)) & mask) + size); | |
72 | ||
73 | if (mprotect (page, end - page, STACK_PROT_RWX) < 0) | |
74 | /* Note that no errors should be emitted by this code; it is | |
75 | considered dangerous for library calls to send messages to | |
76 | stdout/stderr. */ | |
77 | abort (); | |
78 | } | |
79 | } |