1// SPDX-License-Identifier: GPL-2.0
2
3#include <errno.h>
4#include <stdbool.h>
5#include <stdio.h>
6#include <stdlib.h>
7#include <string.h>
8#include <sys/stat.h>
9#include <unistd.h>
10#include <linux/limits.h>
11
12#include "../kselftest.h"
13
14#define MIN_TTY_PATH_LEN 8
15
16static bool tty_valid(char *tty)
17{
18 if (strlen(tty) < MIN_TTY_PATH_LEN)
19 return false;
20
21 if (strncmp(tty, "/dev/tty", MIN_TTY_PATH_LEN) == 0 ||
22 strncmp(tty, "/dev/pts", MIN_TTY_PATH_LEN) == 0)
23 return true;
24
25 return false;
26}
27
28static int write_dev_tty(void)
29{
30 FILE *f;
31 int r = 0;
32
33 f = fopen("/dev/tty", "r+");
34 if (!f)
35 return -errno;
36
37 r = fprintf(f, "hello, world!\n");
38 if (r != strlen("hello, world!\n"))
39 r = -EIO;
40
41 fclose(f);
42 return r;
43}
44
45int main(int argc, char **argv)
46{
47 int r;
48 char tty[PATH_MAX] = {};
49 struct stat st1, st2;
50
51 ksft_print_header();
52 ksft_set_plan(plan: 1);
53
54 r = readlink("/proc/self/fd/0", tty, PATH_MAX);
55 if (r < 0)
56 ksft_exit_fail_msg(msg: "readlink on /proc/self/fd/0 failed: %m\n");
57
58 if (!tty_valid(tty))
59 ksft_exit_skip(msg: "invalid tty path '%s'\n", tty);
60
61 r = stat(tty, &st1);
62 if (r < 0)
63 ksft_exit_fail_msg(msg: "stat failed on tty path '%s': %m\n", tty);
64
65 /* We need to wait at least 8 seconds in order to observe timestamp change */
66 /* https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fbf47635315ab308c9b58a1ea0906e711a9228de */
67 sleep(10);
68
69 r = write_dev_tty();
70 if (r < 0)
71 ksft_exit_fail_msg(msg: "failed to write to /dev/tty: %s\n",
72 strerror(-r));
73
74 r = stat(tty, &st2);
75 if (r < 0)
76 ksft_exit_fail_msg(msg: "stat failed on tty path '%s': %m\n", tty);
77
78 /* We wrote to the terminal so timestamps should have been updated */
79 if (st1.st_atim.tv_sec == st2.st_atim.tv_sec &&
80 st1.st_mtim.tv_sec == st2.st_mtim.tv_sec) {
81 ksft_test_result_fail(msg: "tty timestamps not updated\n");
82 ksft_exit_fail();
83 }
84
85 ksft_test_result_pass(
86 msg: "timestamps of terminal '%s' updated after write to /dev/tty\n", tty);
87 return EXIT_SUCCESS;
88}
89

source code of linux/tools/testing/selftests/tty/tty_tstamp_update.c