1/* Stack executability handling for GNU dynamic linker. Linux version.
2 Copyright (C) 2003-2017 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#include <ldsodefs.h>
20#include <sys/mman.h>
21#include <errno.h>
22#include <libintl.h>
23#include <stdbool.h>
24#include <stackinfo.h>
25#include <caller.h>
26#include <sysdep.h>
27
28
29extern int __stack_prot attribute_relro attribute_hidden;
30
31
32int
33internal_function
34_dl_make_stack_executable (void **stack_endp)
35{
36 /* This gives us the highest/lowest page that needs to be changed. */
37 uintptr_t page = ((uintptr_t) *stack_endp
38 & -(intptr_t) GLRO(dl_pagesize));
39 int result = 0;
40
41 /* Challenge the caller. */
42 if (__builtin_expect (__check_caller (RETURN_ADDRESS (0),
43 allow_ldso|allow_libpthread) != 0, 0)
44 || __builtin_expect (*stack_endp != __libc_stack_end, 0))
45 return EPERM;
46
47 if (__builtin_expect (__mprotect ((void *) page, GLRO(dl_pagesize),
48 __stack_prot) == 0, 1))
49 goto return_success;
50 result = errno;
51 goto out;
52
53 return_success:
54 /* Clear the address. */
55 *stack_endp = NULL;
56
57 /* Remember that we changed the permission. */
58 GL(dl_stack_flags) |= PF_X;
59
60 out:
61#ifdef check_consistency
62 check_consistency ();
63#endif
64
65 return result;
66}
67rtld_hidden_def (_dl_make_stack_executable)
68