1 /*
2 * Copyright (c) 2019 Intel Corporation.
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7 #include <zephyr/internal/syscall_handler.h>
8 #include <zephyr/logging/log.h>
9
10 LOG_MODULE_REGISTER(app_syscall);
11
12 /* Implementation of magic_syscall() which is a system call just for this
13 * application, not part of the kernel codebase.
14 *
15 * It's trivial, update the supplied cookie value by 1, only if it is less than
16 * 42. This is just for demonstration purposes to show how syscalls can be
17 * defined in application code.
18 */
z_impl_magic_syscall(unsigned int * cookie)19 int z_impl_magic_syscall(unsigned int *cookie)
20 {
21 LOG_DBG("magic syscall: got a cookie %u", *cookie);
22
23 if (*cookie > 42) {
24 LOG_ERR("bad cookie :(");
25 return -EINVAL;
26 }
27
28 *cookie = *cookie + 1;
29
30 return 0;
31 }
32
z_vrfy_magic_syscall(unsigned int * cookie)33 static int z_vrfy_magic_syscall(unsigned int *cookie)
34 {
35 unsigned int cookie_copy;
36 int ret;
37
38 /* Confirm that this user-supplied pointer is valid memory that
39 * can be accessed. If it's OK, copy into cookie_copy.
40 */
41 if (k_usermode_from_copy(&cookie_copy, cookie, sizeof(*cookie)) != 0) {
42 return -EPERM;
43 }
44
45 /* We pass to the implementation the *copy*, to prevent TOCTOU attacks
46 */
47 ret = z_impl_magic_syscall(&cookie_copy);
48
49 if (ret == 0 &&
50 k_usermode_to_copy(cookie, &cookie_copy, sizeof(*cookie)) != 0) {
51 return -EPERM;
52 }
53
54 return ret;
55 }
56
57 #include <syscalls/magic_syscall_mrsh.c>
58
