path: root/kernel/time/time.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  This file contains the interface functions for the various time related
 *  system calls: time, stime, gettimeofday, settimeofday, adjtime
 *
 * Modification history:
 *
 * 1993-09-02    Philip Gladstone
 *      Created file with time related functions from sched/core.c and adjtimex()
 * 1993-10-08    Torsten Duwe
 *      adjtime interface update and CMOS clock write code
 * 1995-08-13    Torsten Duwe
 *      kernel PLL updated to 1994-12-13 specs (rfc-1589)
 * 1999-01-16    Ulrich Windl
 *	Introduced error checking for many cases in adjtimex().
 *	Updated NTP code according to technical memorandum Jan '96
 *	"A Kernel Model for Precision Timekeeping" by Dave Mills
 *	Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
 *	(Even though the technical memorandum forbids it)
 * 2004-07-14	 Christoph Lameter
 *	Added getnstimeofday to allow the posix timer functions to return
 *	with nanosecond accuracy
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/timex.h>
#include <linux/capability.h>
#include <linux/timekeeper_internal.h>
#include <linux/errno.h>
#include <linux/syscalls.h>
#include <linux/security.h>
#include <linux/fs.h>
#include <linux/math64.h>
#include <linux/ptrace.h>

#include <linux/uaccess.h>
#include <linux/compat.h>
#include <asm/unistd.h>

#include <generated/timeconst.h>
#include "timekeeping.h"

/*
 * The timezone where the local system is located.  Used as a default by some
 * programs who obtain this value by using gettimeofday.
 */
struct timezone sys_tz;

EXPORT_SYMBOL(sys_tz);

#ifdef __ARCH_WANT_SYS_TIME

/*
 * sys_time() can be implemented in user-level using
 * sys_gettimeofday().  Is this for backwards compatibility?  If so,
 * why not move it into the appropriate arch directory (for those
 * architectures that need it).
 */
SYSCALL_DEFINE1(time, __kernel_old_time_t __user *, tloc)
{
	__kernel_old_time_t i = (__kernel_old_time_t)ktime_get_real_seconds();

	if (tloc) {
		if (put_user(i,tloc))
			return -EFAULT;
	}
	force_successful_syscall_return();
	return i;
}

/*
 * sys_stime() can be implemented in user-level using
 * sys_settimeofday().  Is this for backwards compatibility?  If so,
 * why not move it into the appropriate arch directory (for those
 * architectures that need it).
 */

SYSCALL_DEFINE1(stime, __kernel_old_time_t __user *, tptr)
{
	struct timespec64 tv;
	int err;

	if (get_user(tv.tv_sec, tptr))
		return -EFAULT;

	tv.tv_nsec = 0;

	err = security_settime64(&tv, NULL);
	if (err)
		return err;

	do_settimeofday64(&tv);
	return 0;
}

#endif /* __ARCH_WANT_SYS_TIME */

#ifdef CONFIG_COMPAT_32BIT_TIME
#ifdef __ARCH_WANT_SYS_TIME32

/* old_time32_t is a 32 bit "long" and needs to get converted. */
SYSCALL_DEFINE1(time32, old_time32_t __user *, tloc)
{
	old_time32_t i;

	i = (old_time32_t)ktime_get_real_seconds();

	if (tloc) {
		if (put_user(i,tloc))
			return -EFAULT;
	}
	force_successful_syscall_return();
	return i;
}

SYSCALL_DEFINE1(stime32, old_time32_t __user *, tptr)
{
	struct timespec64 tv;
	int err;

	if (get_user(tv.tv_sec, tptr))
		return -EFAULT;

	tv.tv_nsec = 0;

	err = security_settime64(&tv, NULL);
	if (err)
		return err;

	do_settimeofday64(&tv);
	return 0;
}

#endif /* __ARCH_WANT_SYS_TIME32 */
#endif

SYSCALL_DEFINE2(gettimeofday, struct __kernel_old_timeval __user *, tv,
		struct timezone __user *, tz)
{
	if (likely(tv != NULL)) {
		struct timespec64 ts;

		ktime_get_real_ts64(&ts);
		if (put_user(ts.tv_sec, &tv->tv_sec) ||
		    put_user(ts.tv_nsec / 1000, &tv->tv_usec))
			return -EFAULT;
	}
	if (unlikely(tz != NULL)) {
		if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
			return -EFAULT;
	}
	return 0;
}

/*
 * In case for some reason the CMOS clock has not already been running
 * in UTC, but in some local time: The first time we set the timezone,
 * we will warp the clock so that it is ticking UTC time instead of
 * local time. Presumably, if someone is setting the timezone then we
 * are running in an environment where the programs understand about
 * timezones. This should be done at boot time in the /etc/rc script,
 * as soon as possible, so that the clock can be set right. Otherwise,
 * various programs will get confused when the clock gets warped.
 */

int do_sys_settimeofday64(const struct timespec64 *tv, const struct timezone *tz)
{
	static int firsttime = 1;
	int error = 0;

	if (tv && !timespec64_valid_settod(tv))
		return -EINVAL;

	error = security_settime64(tv, tz);
	if (error)
		return error;

	if (tz) {
		/* Verify we're within the +-15 hrs range */
		if (tz->tz_minuteswest > 15*60 || tz->tz_minuteswest < -15*60)
			return -EINVAL;

		sys_tz = *tz;
		update_vsyscall_tz();
		if (firsttime) {
			firsttime = 0;
			if (!tv)
				timekeeping_warp_clock();
		}
	}
	if (tv)
		return do_settimeofday64(tv);
	return 0;
}

SYSCALL_DEFINE2(settimeofday, struct __kernel_old_timeval __user *, tv,
		struct timezone __user *, tz)
{
	struct timespec64 new_ts;
	struct timezone new_tz;

	if (tv) {
		if (get_user(new_ts.tv_sec, &tv->tv_sec) ||
		    get_user(new_ts.tv_nsec, &tv->tv_usec))
			return -EFAULT;

		if (new_ts.tv_nsec > USEC_PER_SEC || new_ts.tv_nsec < 0)
			return -EINVAL;

		new_ts.tv_nsec *= NSEC_PER_USEC;
	}
	if (tz) {
		if (copy_from_user(&new_tz, tz, sizeof(*tz)))
			return -EFAULT;
	}

	return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz