1/* Stack executability handling for GNU dynamic linker. Linux version.
2 Copyright (C) 2003-2018 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
33_dl_make_stack_executable (void **stack_endp)
34{
35 /* This gives us the highest/lowest page that needs to be changed. */
36 uintptr_t page = ((uintptr_t) *stack_endp
37 & -(intptr_t) GLRO(dl_pagesize));
38 int result = 0;
39
40 /* Challenge the caller. */
41 if (__builtin_expect (__check_caller (RETURN_ADDRESS (0),
42 allow_ldso|allow_libpthread) != 0, 0)
43 || __builtin_expect (*stack_endp != __libc_stack_end, 0))
44 return EPERM;
45
46 if (__builtin_expect (__mprotect ((void *) page, GLRO(dl_pagesize),
47 __stack_prot) == 0, 1))
48 goto return_success;
49 result = errno;
50 goto out;
51
52 return_success:
53 /* Clear the address. */
54 *stack_endp = NULL;
55
56 /* Remember that we changed the permission. */
57 GL(dl_stack_flags) |= PF_X;
58
59 out:
60#ifdef check_consistency
61 check_consistency ();
62#endif
63
64 return result;
65}
66rtld_hidden_def (_dl_make_stack_executable)
67