1/* Stack executability handling for GNU dynamic linker. Linux version.
2 Copyright (C) 2003-2021 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 <https://www.gnu.org/licenses/>. */
18
19#include <errno.h>
20#include <ldsodefs.h>
21#include <libintl.h>
22#include <list.h>
23#include <pthreadP.h>
24#include <stackinfo.h>
25#include <stdbool.h>
26#include <sys/mman.h>
27#include <sysdep.h>
28#include <unistd.h>
29
30extern int __stack_prot attribute_relro attribute_hidden;
31
32static int
33make_main_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 if (__builtin_expect (__mprotect ((void *) page, GLRO(dl_pagesize),
41 __stack_prot) == 0, 1))
42 goto return_success;
43 result = errno;
44 goto out;
45
46 return_success:
47 /* Clear the address. */
48 *stack_endp = NULL;
49
50 /* Remember that we changed the permission. */
51 GL(dl_stack_flags) |= PF_X;
52
53 out:
54#ifdef check_consistency
55 check_consistency ();
56#endif
57
58 return result;
59}
60
61int
62_dl_make_stacks_executable (void **stack_endp)
63{
64 /* First the main thread's stack. */
65 int err = make_main_stack_executable (stack_endp);
66 if (err != 0)
67 return err;
68
69 lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
70
71 list_t *runp;
72 list_for_each (runp, &GL (dl_stack_used))
73 {
74 err = __nptl_change_stack_perm (list_entry (runp, struct pthread, list));
75 if (err != 0)
76 break;
77 }
78
79 /* Also change the permission for the currently unused stacks. This
80 might be wasted time but better spend it here than adding a check
81 in the fast path. */
82 if (err == 0)
83 list_for_each (runp, &GL (dl_stack_cache))
84 {
85 err = __nptl_change_stack_perm (list_entry (runp, struct pthread,
86 list));
87 if (err != 0)
88 break;
89 }
90
91 lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
92
93 return err;
94}
95
96int
97__nptl_change_stack_perm (struct pthread *pd)
98{
99#ifdef NEED_SEPARATE_REGISTER_STACK
100 size_t pagemask = __getpagesize () - 1;
101 void *stack = (pd->stackblock
102 + (((((pd->stackblock_size - pd->guardsize) / 2)
103 & pagemask) + pd->guardsize) & pagemask));
104 size_t len = pd->stackblock + pd->stackblock_size - stack;
105#elif _STACK_GROWS_DOWN
106 void *stack = pd->stackblock + pd->guardsize;
107 size_t len = pd->stackblock_size - pd->guardsize;
108#elif _STACK_GROWS_UP
109 void *stack = pd->stackblock;
110 size_t len = (uintptr_t) pd - pd->guardsize - (uintptr_t) pd->stackblock;
111#else
112# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
113#endif
114 if (__mprotect (stack, len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
115 return errno;
116
117 return 0;
118}
119rtld_hidden_def (__nptl_change_stack_perm)
120