tty_tstamp_update.c

  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	int result = KSFT_FAIL;
 51
 52	ksft_print_header();
 53	ksft_set_plan(1);
 54
 55	r = readlink("/proc/self/fd/0", tty, PATH_MAX);
 56	if (r < 0) {
 57		ksft_print_msg("readlink on /proc/self/fd/0 failed: %m\n");
 58		goto out;
 59	}
 60
 61	if (!tty_valid(tty)) {
 62		ksft_print_msg("invalid tty path '%s'\n", tty);
 63		result = KSFT_SKIP;
 64		goto out;
 65
 66	}
 67
 68	r = stat(tty, &st1);
 69	if (r < 0) {
 70		ksft_print_msg("stat failed on tty path '%s': %m\n", tty);
 71		goto out;
 72	}
 73
 74	/* We need to wait at least 8 seconds in order to observe timestamp change */
 75	/* https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fbf47635315ab308c9b58a1ea0906e711a9228de */
 76	sleep(10);
 77
 78	r = write_dev_tty();
 79	if (r < 0) {
 80		ksft_print_msg("failed to write to /dev/tty: %s\n",
 81			       strerror(-r));
 82		goto out;
 83	}
 84
 85	r = stat(tty, &st2);
 86	if (r < 0) {
 87		ksft_print_msg("stat failed on tty path '%s': %m\n", tty);
 88		goto out;
 89	}
 90
 91	/* We wrote to the terminal so timestamps should have been updated */
 92	if (st1.st_atim.tv_sec == st2.st_atim.tv_sec &&
 93	    st1.st_mtim.tv_sec == st2.st_mtim.tv_sec) {
 94		ksft_print_msg("tty timestamps not updated\n");
 95		goto out;
 96	}
 97
 98	ksft_print_msg(
 99		"timestamps of terminal '%s' updated after write to /dev/tty\n", tty);
100	result = KSFT_PASS;
101
102out:
103	ksft_test_result_report(result, "tty_tstamp_update\n");
104
105	ksft_finished();
106}