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(1);
53
54	r = readlink("/proc/self/fd/0", tty, PATH_MAX);
55	if (r < 0)
56		ksft_exit_fail_msg("readlink on /proc/self/fd/0 failed: %m\n");
57
58	if (!tty_valid(tty))
59		ksft_exit_skip("invalid tty path '%s'\n", tty);
60
61	r = stat(tty, &st1);
62	if (r < 0)
63		ksft_exit_fail_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("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("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("tty timestamps not updated\n");
82		ksft_exit_fail();
83	}
84
85	ksft_test_result_pass(
86		"timestamps of terminal '%s' updated after write to /dev/tty\n", tty);
87	return EXIT_SUCCESS;
88}