Merge tag 'timers-ptp-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timekeeping and VDSO updates from Thomas Gleixner:

 - Introduce support for auxiliary timekeepers

   PTP clocks can be disconnected from the universal CLOCK_TAI reality
   for various reasons including regularatory requirements for
   functional safety redundancy.

   The kernel so far only supports a single notion of time, which means
   that all clocks are correlated in frequency and only differ by offset
   to each other.

   Access to non-correlated PTP clocks has been available so far only
   through the file descriptor based "POSIX clock IDs", which are
   subject to locking and have to go all the way out to the hardware.

   The access is not only horribly slow, as it has to go all the way out
   to the NIC/PTP hardware, but that also prevents the kernel to read
   the time of such clocks e.g. from the network stack, where it is
   required for TSN networking both on the transmit and receive side
   unless the hardware provides offloading.

   The auxiliary clocks provide a mechanism to support arbitrary clocks
   which are not correlated to the system clock. This is not restricted
   to the PTP use case on purpose as there is no kernel side association
   of these clocks to a particular PTP device because that's a pure user
   space configuration decision. Having them independent allows to
   utilize them for other purposes and also enables them to be tested
   without hardware dependencies.

   To avoid pointless overhead these clocks have to be enabled
   individualy via a new sysfs interface to reduce the overhead to a
   single compare in the hotpath if they are enabled at the Kconfig
   level at all.

   These clocks utilize the existing timekeeping/NTP infrastructures,
   which has been made possible over the recent releases by incrementaly
   converting these infrastructures over from a single static instance
   to a multi-instance pointer based implementation without any
   performance regression reported.

   The auxiliary clocks provide the same "emulation" of a "correct"
   clock as the existing CLOCK_* variants do with an independent
   instance of data and provide the same steering mechanism through the
   existing sys_clock_adjtime() interface, which has been confirmed to
   work by the chronyd(8) maintainer.

   That allows to provide lockless kernel internal and VDSO support so
   that applications and kernel internal functionalities can access
   these clocks without restrictions and at the same performance as the
   existing system clocks.

 - Avoid double notifications in the adjtimex() syscall. Not a big
   issue, but a trivial to avoid latency source.

* tag 'timers-ptp-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits)
  vdso/gettimeofday: Add support for auxiliary clocks
  vdso/vsyscall: Update auxiliary clock data in the datapage
  vdso: Introduce aux_clock_resolution_ns()
  vdso/gettimeofday: Introduce vdso_get_timestamp()
  vdso/gettimeofday: Introduce vdso_set_timespec()
  vdso/gettimeofday: Introduce vdso_clockid_valid()
  vdso/gettimeofday: Return bool from clock_gettime() helpers
  vdso/gettimeofday: Return bool from clock_getres() helpers
  vdso/helpers: Add helpers for seqlocks of single vdso_clock
  vdso/vsyscall: Split up __arch_update_vsyscall() into __arch_update_vdso_clock()
  vdso/vsyscall: Introduce a helper to fill clock configurations
  timekeeping: Remove the temporary CLOCK_AUX workaround
  timekeeping: Provide ktime_get_clock_ts64()
  timekeeping: Provide interface to control auxiliary clocks
  timekeeping: Provide update for auxiliary timekeepers
  timekeeping: Provide adjtimex() for auxiliary clocks
  timekeeping: Prepare do_adtimex() for auxiliary clocks
  timekeeping: Make do_adjtimex() reusable
  timekeeping: Add auxiliary clock support to __timekeeping_inject_offset()
  timekeeping: Make timekeeping_inject_offset() reusable
  ...

1 files changed, 554 insertions, 75 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 83c65f3afcca..059fa8b79be6 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -6,6 +6,7 @@
 #include <linux/timekeeper_internal.h>
 #include <linux/module.h>
 #include <linux/interrupt.h>
+#include <linux/kobject.h>
 #include <linux/percpu.h>
 #include <linux/init.h>
 #include <linux/mm.h>
@@ -25,6 +26,8 @@
 #include <linux/audit.h>
 #include <linux/random.h>
 
+#include <vdso/auxclock.h>
+
 #include "tick-internal.h"
 #include "ntp_internal.h"
 #include "timekeeping_internal.h"
@@ -53,7 +56,32 @@ struct tk_data {
 	raw_spinlock_t		lock;
 } ____cacheline_aligned;
 
-static struct tk_data tk_core;
+static struct tk_data timekeeper_data[TIMEKEEPERS_MAX];
+
+/* The core timekeeper */
+#define tk_core		(timekeeper_data[TIMEKEEPER_CORE])
+
+#ifdef CONFIG_POSIX_AUX_CLOCKS
+static inline bool tk_get_aux_ts64(unsigned int tkid, struct timespec64 *ts)
+{
+	return ktime_get_aux_ts64(CLOCK_AUX + tkid - TIMEKEEPER_AUX_FIRST, ts);
+}
+
+static inline bool tk_is_aux(const struct timekeeper *tk)
+{
+	return tk->id >= TIMEKEEPER_AUX_FIRST && tk->id <= TIMEKEEPER_AUX_LAST;
+}
+#else
+static inline bool tk_get_aux_ts64(unsigned int tkid, struct timespec64 *ts)
+{
+	return false;
+}
+
+static inline bool tk_is_aux(const struct timekeeper *tk)
+{
+	return false;
+}
+#endif
 
 /* flag for if timekeeping is suspended */
 int __read_mostly timekeeping_suspended;
@@ -113,6 +141,16 @@ static struct tk_fast tk_fast_raw  ____cacheline_aligned = {
 	.base[1] = FAST_TK_INIT,
 };
 
+#ifdef CONFIG_POSIX_AUX_CLOCKS
+static __init void tk_aux_setup(void);
+static void tk_aux_update_clocksource(void);
+static void tk_aux_advance(void);
+#else
+static inline void tk_aux_setup(void) { }
+static inline void tk_aux_update_clocksource(void) { }
+static inline void tk_aux_advance(void) { }
+#endif
+
 unsigned long timekeeper_lock_irqsave(void)
 {
 	unsigned long flags;
@@ -601,7 +639,7 @@ EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
  */
 static inline void tk_update_leap_state(struct timekeeper *tk)
 {
-	tk->next_leap_ktime = ntp_get_next_leap();
+	tk->next_leap_ktime = ntp_get_next_leap(tk->id);
 	if (tk->next_leap_ktime != KTIME_MAX)
 		/* Convert to monotonic time */
 		tk->next_leap_ktime = ktime_sub(tk->next_leap_ktime, tk->offs_real);
@@ -663,7 +701,7 @@ static void timekeeping_restore_shadow(struct tk_data *tkd)
 
 static void timekeeping_update_from_shadow(struct tk_data *tkd, unsigned int action)
 {
-	struct timekeeper *tk = &tk_core.shadow_timekeeper;
+	struct timekeeper *tk = &tkd->shadow_timekeeper;
 
 	lockdep_assert_held(&tkd->lock);
 
@@ -678,18 +716,22 @@ static void timekeeping_update_from_shadow(struct tk_data *tkd, unsigned int act
 
 	if (action & TK_CLEAR_NTP) {
 		tk->ntp_error = 0;
-		ntp_clear();
+		ntp_clear(tk->id);
 	}
 
 	tk_update_leap_state(tk);
 	tk_update_ktime_data(tk);
+	tk->tkr_mono.base_real = tk->tkr_mono.base + tk->offs_real;
 
-	update_vsyscall(tk);
-	update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
+	if (tk->id == TIMEKEEPER_CORE) {
+		update_vsyscall(tk);
+		update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
 
-	tk->tkr_mono.base_real = tk->tkr_mono.base + tk->offs_real;
-	update_fast_timekeeper(&tk->tkr_mono, &tk_fast_mono);
-	update_fast_timekeeper(&tk->tkr_raw,  &tk_fast_raw);
+		update_fast_timekeeper(&tk->tkr_mono, &tk_fast_mono);
+		update_fast_timekeeper(&tk->tkr_raw,  &tk_fast_raw);
+	} else if (tk_is_aux(tk)) {
+		vdso_time_update_aux(tk);
+	}
 
 	if (action & TK_CLOCK_WAS_SET)
 		tk->clock_was_set_seq++;
@@ -975,9 +1017,14 @@ time64_t ktime_get_real_seconds(void)
 EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
 
 /**
- * __ktime_get_real_seconds - The same as ktime_get_real_seconds
- * but without the sequence counter protect. This internal function
- * is called just when timekeeping lock is already held.
+ * __ktime_get_real_seconds - Unprotected access to CLOCK_REALTIME seconds
+ *
+ * The same as ktime_get_real_seconds() but without the sequence counter
+ * protection. This function is used in restricted contexts like the x86 MCE
+ * handler and in KGDB. It's unprotected on 32-bit vs. concurrent half
+ * completed modification and only to be used for such critical contexts.
+ *
+ * Returns: Racy snapshot of the CLOCK_REALTIME seconds value
  */
 noinstr time64_t __ktime_get_real_seconds(void)
 {
@@ -1412,41 +1459,73 @@ int do_settimeofday64(const struct timespec64 *ts)
 }
 EXPORT_SYMBOL(do_settimeofday64);
 
+static inline bool timekeeper_is_core_tk(struct timekeeper *tk)
+{
+	return !IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS) || tk->id == TIMEKEEPER_CORE;
+}
+
 /**
- * timekeeping_inject_offset - Adds or subtracts from the current time.
+ * __timekeeping_inject_offset - Adds or subtracts from the current time.
+ * @tkd:	Pointer to the timekeeper to modify
  * @ts:		Pointer to the timespec variable containing the offset
  *
  * Adds or subtracts an offset value from the current time.
  */
-static int timekeeping_inject_offset(const struct timespec64 *ts)
+static int __timekeeping_inject_offset(struct tk_data *tkd, const struct timespec64 *ts)
 {
+	struct timekeeper *tks = &tkd->shadow_timekeeper;
+	struct timespec64 tmp;
+
 	if (ts->tv_nsec < 0 || ts->tv_nsec >= NSEC_PER_SEC)
 		return -EINVAL;
 
-	scoped_guard (raw_spinlock_irqsave, &tk_core.lock) {
-		struct timekeeper *tks = &tk_core.shadow_timekeeper;
-		struct timespec64 tmp;
-
-		timekeeping_forward_now(tks);
+	timekeeping_forward_now(tks);
 
+	if (timekeeper_is_core_tk(tks)) {
 		/* Make sure the proposed value is valid */
 		tmp = timespec64_add(tk_xtime(tks), *ts);
 		if (timespec64_compare(&tks->wall_to_monotonic, ts) > 0 ||
 		    !timespec64_valid_settod(&tmp)) {
-			timekeeping_restore_shadow(&tk_core);
+			timekeeping_restore_shadow(tkd);
 			return -EINVAL;
 		}
 
 		tk_xtime_add(tks, ts);
 		tk_set_wall_to_mono(tks, timespec64_sub(tks->wall_to_monotonic, *ts));
-		timekeeping_update_from_shadow(&tk_core, TK_UPDATE_ALL);
+	} else {
+		struct tk_read_base *tkr_mono = &tks->tkr_mono;
+		ktime_t now, offs;
+
+		/* Get the current time */
+		now = ktime_add_ns(tkr_mono->base, timekeeping_get_ns(tkr_mono));
+		/* Add the relative offset change */
+		offs = ktime_add(tks->offs_aux, timespec64_to_ktime(*ts));
+
+		/* Prevent that the resulting time becomes negative */
+		if (ktime_add(now, offs) < 0) {
+			timekeeping_restore_shadow(tkd);
+			return -EINVAL;
+		}
+		tks->offs_aux = offs;
 	}
 
-	/* Signal hrtimers about time change */
-	clock_was_set(CLOCK_SET_WALL);
+	timekeeping_update_from_shadow(tkd, TK_UPDATE_ALL);
 	return 0;
 }
 
+static int timekeeping_inject_offset(const struct timespec64 *ts)
+{
+	int ret;
+
+	scoped_guard (raw_spinlock_irqsave, &tk_core.lock)
+		ret = __timekeeping_inject_offset(&tk_core, ts);
+
+	/* Signal hrtimers about time change */
+	if (!ret)
+		clock_was_set(CLOCK_SET_WALL);
+	return ret;
+}
+
 /*
  * Indicates if there is an offset between the system clock and the hardware
  * clock/persistent clock/rtc.
@@ -1522,6 +1601,8 @@ static int change_clocksource(void *data)
 		timekeeping_update_from_shadow(&tk_core, TK_UPDATE_ALL);
 	}
 
+	tk_aux_update_clocksource();
+
 	if (old) {
 		if (old->disable)
 			old->disable(old);
@@ -1573,6 +1654,39 @@ void ktime_get_raw_ts64(struct timespec64 *ts)
 }
 EXPORT_SYMBOL(ktime_get_raw_ts64);
 
+/**
+ * ktime_get_clock_ts64 - Returns time of a clock in a timespec
+ * @id:		POSIX clock ID of the clock to read
+ * @ts:		Pointer to the timespec64 to be set
+ *
+ * The timestamp is invalidated (@ts->sec is set to -1) if the
+ * clock @id is not available.
+ */
+void ktime_get_clock_ts64(clockid_t id, struct timespec64 *ts)
+{
+	/* Invalidate time stamp */
+	ts->tv_sec = -1;
+	ts->tv_nsec = 0;
+
+	switch (id) {
+	case CLOCK_REALTIME:
+		ktime_get_real_ts64(ts);
+		return;
+	case CLOCK_MONOTONIC:
+		ktime_get_ts64(ts);
+		return;
+	case CLOCK_MONOTONIC_RAW:
+		ktime_get_raw_ts64(ts);
+		return;
+	case CLOCK_AUX ... CLOCK_AUX_LAST:
+		if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS))
+			ktime_get_aux_ts64(id, ts);
+		return;
+	default:
+		WARN_ON_ONCE(1);
+	}
+}
+EXPORT_SYMBOL_GPL(ktime_get_clock_ts64);
 
 /**
  * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
@@ -1649,10 +1763,12 @@ read_persistent_wall_and_boot_offset(struct timespec64 *wall_time,
 	*boot_offset = ns_to_timespec64(local_clock());
 }
 
-static __init void tkd_basic_setup(struct tk_data *tkd)
+static __init void tkd_basic_setup(struct tk_data *tkd, enum timekeeper_ids tk_id, bool valid)
 {
 	raw_spin_lock_init(&tkd->lock);
 	seqcount_raw_spinlock_init(&tkd->seq, &tkd->lock);
+	tkd->timekeeper.id = tkd->shadow_timekeeper.id = tk_id;
+	tkd->timekeeper.clock_valid = tkd->shadow_timekeeper.clock_valid = valid;
 }
 
 /*
@@ -1682,7 +1798,8 @@ void __init timekeeping_init(void)
 	struct timekeeper *tks = &tk_core.shadow_timekeeper;
 	struct clocksource *clock;
 
-	tkd_basic_setup(&tk_core);
+	tkd_basic_setup(&tk_core, TIMEKEEPER_CORE, true);
+	tk_aux_setup();
 
 	read_persistent_wall_and_boot_offset(&wall_time, &boot_offset);
 	if (timespec64_valid_settod(&wall_time) &&
@@ -2034,7 +2151,7 @@ static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
  */
 static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
 {
-	u64 ntp_tl = ntp_tick_length();
+	u64 ntp_tl = ntp_tick_length(tk->id);
 	u32 mult;
 
 	/*
@@ -2115,7 +2232,7 @@ static inline unsigned int accumulate_nsecs_to_secs(struct timekeeper *tk)
 		}
 
 		/* Figure out if its a leap sec and apply if needed */
-		leap = second_overflow(tk->xtime_sec);
+		leap = second_overflow(tk->id, tk->xtime_sec);
 		if (unlikely(leap)) {
 			struct timespec64 ts;
 
@@ -2181,16 +2298,14 @@ static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
  * timekeeping_advance - Updates the timekeeper to the current time and
  * current NTP tick length
  */
-static bool timekeeping_advance(enum timekeeping_adv_mode mode)
+static bool __timekeeping_advance(struct tk_data *tkd, enum timekeeping_adv_mode mode)
 {
-	struct timekeeper *tk = &tk_core.shadow_timekeeper;
-	struct timekeeper *real_tk = &tk_core.timekeeper;
+	struct timekeeper *tk = &tkd->shadow_timekeeper;
+	struct timekeeper *real_tk = &tkd->timekeeper;
 	unsigned int clock_set = 0;
 	int shift = 0, maxshift;
 	u64 offset, orig_offset;
 
-	guard(raw_spinlock_irqsave)(&tk_core.lock);
-
 	/* Make sure we're fully resumed: */
 	if (unlikely(timekeeping_suspended))
 		return false;
@@ -2214,7 +2329,7 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode)
 	shift = ilog2(offset) - ilog2(tk->cycle_interval);
 	shift = max(0, shift);
 	/* Bound shift to one less than what overflows tick_length */
-	maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
+	maxshift = (64 - (ilog2(ntp_tick_length(tk->id)) + 1)) - 1;
 	shift = min(shift, maxshift);
 	while (offset >= tk->cycle_interval) {
 		offset = logarithmic_accumulation(tk, offset, shift, &clock_set);
@@ -2239,19 +2354,27 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode)
 	if (orig_offset != offset)
 		tk_update_coarse_nsecs(tk);
 
-	timekeeping_update_from_shadow(&tk_core, clock_set);
+	timekeeping_update_from_shadow(tkd, clock_set);
 
 	return !!clock_set;
 }
 
+static bool timekeeping_advance(enum timekeeping_adv_mode mode)
+{
+	guard(raw_spinlock_irqsave)(&tk_core.lock);
+	return __timekeeping_advance(&tk_core, mode);
+}
+
 /**
  * update_wall_time - Uses the current clocksource to increment the wall time
  *
+ * It also updates the enabled auxiliary clock timekeepers
  */
 void update_wall_time(void)
 {
 	if (timekeeping_advance(TK_ADV_TICK))
 		clock_was_set_delayed();
+	tk_aux_advance();
 }
 
 /**
@@ -2449,7 +2572,7 @@ ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
 /*
  * timekeeping_validate_timex - Ensures the timex is ok for use in do_adjtimex
  */
-static int timekeeping_validate_timex(const struct __kernel_timex *txc)
+static int timekeeping_validate_timex(const struct __kernel_timex *txc, bool aux_clock)
 {
 	if (txc->modes & ADJ_ADJTIME) {
 		/* singleshot must not be used with any other mode bits */
@@ -2508,6 +2631,20 @@ static int timekeeping_validate_timex(const struct __kernel_timex *txc)
 			return -EINVAL;
 	}
 
+	if (aux_clock) {
+		/* Auxiliary clocks are similar to TAI and do not have leap seconds */
+		if (txc->status & (STA_INS | STA_DEL))
+			return -EINVAL;
+
+		/* No TAI offset setting */
+		if (txc->modes & ADJ_TAI)
+			return -EINVAL;
+
+		/* No PPS support either */
+		if (txc->status & (STA_PPSFREQ | STA_PPSTIME))
+			return -EINVAL;
+	}
+
 	return 0;
 }
 
@@ -2526,74 +2663,103 @@ unsigned long random_get_entropy_fallback(void)
 }
 EXPORT_SYMBOL_GPL(random_get_entropy_fallback);
 
-/**
- * do_adjtimex() - Accessor function to NTP __do_adjtimex function
- * @txc:	Pointer to kernel_timex structure containing NTP parameters
- */
-int do_adjtimex(struct __kernel_timex *txc)
+struct adjtimex_result {
+	struct audit_ntp_data	ad;
+	struct timespec64	delta;
+	bool			clock_set;
+};
+
+static int __do_adjtimex(struct tk_data *tkd, struct __kernel_timex *txc,
+			 struct adjtimex_result *result)
 {
-	struct audit_ntp_data ad;
-	bool offset_set = false;
-	bool clock_set = false;
+	struct timekeeper *tks = &tkd->shadow_timekeeper;
+	bool aux_clock = !timekeeper_is_core_tk(tks);
 	struct timespec64 ts;
+	s32 orig_tai, tai;
 	int ret;
 
 	/* Validate the data before disabling interrupts */
-	ret = timekeeping_validate_timex(txc);
+	ret = timekeeping_validate_timex(txc, aux_clock);
 	if (ret)
 		return ret;
 	add_device_randomness(txc, sizeof(*txc));
 
-	if (txc->modes & ADJ_SETOFFSET) {
-		struct timespec64 delta;
+	if (!aux_clock)
+		ktime_get_real_ts64(&ts);
+	else
+		tk_get_aux_ts64(tkd->timekeeper.id, &ts);
 
-		delta.tv_sec  = txc->time.tv_sec;
-		delta.tv_nsec = txc->time.tv_usec;
+	add_device_randomness(&ts, sizeof(ts));
+
+	guard(raw_spinlock_irqsave)(&tkd->lock);
+
+	if (!tks->clock_valid)
+		return -ENODEV;
+
+	if (txc->modes & ADJ_SETOFFSET) {
+		result->delta.tv_sec  = txc->time.tv_sec;
+		result->delta.tv_nsec = txc->time.tv_usec;
 		if (!(txc->modes & ADJ_NANO))
-			delta.tv_nsec *= 1000;
-		ret = timekeeping_inject_offset(&delta);
+			result->delta.tv_nsec *= 1000;
+		ret = __timekeeping_inject_offset(tkd, &result->delta);
 		if (ret)
 			return ret;
-
-		offset_set = delta.tv_sec != 0;
-		audit_tk_injoffset(delta);
+		result->clock_set = true;
 	}
 
-	audit_ntp_init(&ad);
+	orig_tai = tai = tks->tai_offset;
+	ret = ntp_adjtimex(tks->id, txc, &ts, &tai, &result->ad);
 
-	ktime_get_real_ts64(&ts);
-	add_device_randomness(&ts, sizeof(ts));
+	if (tai != orig_tai) {
+		__timekeeping_set_tai_offset(tks, tai);
+		timekeeping_update_from_shadow(tkd, TK_CLOCK_WAS_SET);
+		result->clock_set = true;
+	} else {
+		tk_update_leap_state_all(&tk_core);
+	}
 
-	scoped_guard (raw_spinlock_irqsave, &tk_core.lock) {
-		struct timekeeper *tks = &tk_core.shadow_timekeeper;
-		s32 orig_tai, tai;
+	/* Update the multiplier immediately if frequency was set directly */
+	if (txc->modes & (ADJ_FREQUENCY | ADJ_TICK))
+		result->clock_set |= __timekeeping_advance(tkd, TK_ADV_FREQ);
 
-		orig_tai = tai = tks->tai_offset;
-		ret = __do_adjtimex(txc, &ts, &tai, &ad);
+	return ret;
+}
 
-		if (tai != orig_tai) {
-			__timekeeping_set_tai_offset(tks, tai);
-			timekeeping_update_from_shadow(&tk_core, TK_CLOCK_WAS_SET);
-			clock_set = true;
-		} else {
-			tk_update_leap_state_all(&tk_core);
-		}
-	}
+/**
+ * do_adjtimex() - Accessor function to NTP __do_adjtimex function
+ * @txc:	Pointer to kernel_timex structure containing NTP parameters
+ */
+int do_adjtimex(struct __kernel_timex *txc)
+{
+	struct adjtimex_result result = { };
+	int ret;
 
-	audit_ntp_log(&ad);
+	ret = __do_adjtimex(&tk_core, txc, &result);
+	if (ret < 0)
+		return ret;
 
-	/* Update the multiplier immediately if frequency was set directly */
-	if (txc->modes & (ADJ_FREQUENCY | ADJ_TICK))
-		clock_set |= timekeeping_advance(TK_ADV_FREQ);
+	if (txc->modes & ADJ_SETOFFSET)
+		audit_tk_injoffset(result.delta);
 
-	if (clock_set)
+	audit_ntp_log(&result.ad);
+
+	if (result.clock_set)
 		clock_was_set(CLOCK_SET_WALL);
 
-	ntp_notify_cmos_timer(offset_set);
+	ntp_notify_cmos_timer(result.delta.tv_sec != 0);
 
 	return ret;
 }
 
+/*
+ * Invoked from NTP with the time keeper lock held, so lockless access is
+ * fine.
+ */
+long ktime_get_ntp_seconds(unsigned int id)
+{
+	return timekeeper_data[id].timekeeper.xtime_sec;
+}
+
 #ifdef CONFIG_NTP_PPS
 /**
  * hardpps() - Accessor function to NTP __hardpps function
@@ -2607,3 +2773,316 @@ void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
 }
 EXPORT_SYMBOL(hardpps);
 #endif /* CONFIG_NTP_PPS */
+
+#ifdef CONFIG_POSIX_AUX_CLOCKS
+#include "posix-timers.h"
+
+/*
+ * Bitmap for the activated auxiliary timekeepers to allow lockless quick
+ * checks in the hot paths without touching extra cache lines. If set, then
+ * the state of the corresponding timekeeper has to be re-checked under
+ * timekeeper::lock.
+ */
+static unsigned long aux_timekeepers;
+
+static inline unsigned int clockid_to_tkid(unsigned int id)
+{
+	return TIMEKEEPER_AUX_FIRST + id - CLOCK_AUX;
+}
+
+static inline struct tk_data *aux_get_tk_data(clockid_t id)
+{
+	if (!clockid_aux_valid(id))
+		return NULL;
+	return &timekeeper_data[clockid_to_tkid(id)];
+}
+
+/* Invoked from timekeeping after a clocksource change */
+static void tk_aux_update_clocksource(void)
+{
+	unsigned long active = READ_ONCE(aux_timekeepers);
+	unsigned int id;
+
+	for_each_set_bit(id, &active, BITS_PER_LONG) {
+		struct tk_data *tkd = &timekeeper_data[id + TIMEKEEPER_AUX_FIRST];
+		struct timekeeper *tks = &tkd->shadow_timekeeper;
+
+		guard(raw_spinlock_irqsave)(&tkd->lock);
+		if (!tks->clock_valid)
+			continue;
+
+		timekeeping_forward_now(tks);
+		tk_setup_internals(tks, tk_core.timekeeper.tkr_mono.clock);
+		timekeeping_update_from_shadow(tkd, TK_UPDATE_ALL);
+	}
+}
+
+static void tk_aux_advance(void)
+{
+	unsigned long active = READ_ONCE(aux_timekeepers);
+	unsigned int id;
+
+	/* Lockless quick check to avoid extra cache lines */
+	for_each_set_bit(id, &active, BITS_PER_LONG) {
+		struct tk_data *aux_tkd = &timekeeper_data[id + TIMEKEEPER_AUX_FIRST];
+
+		guard(raw_spinlock)(&aux_tkd->lock);
+		if (aux_tkd->shadow_timekeeper.clock_valid)
+			__timekeeping_advance(aux_tkd, TK_ADV_TICK);
+	}
+}
+
+/**
+ * ktime_get_aux - Get time for a AUX clock
+ * @id:	ID of the clock to read (CLOCK_AUX...)
+ * @kt:	Pointer to ktime_t to store the time stamp
+ *
+ * Returns: True if the timestamp is valid, false otherwise
+ */
+bool ktime_get_aux(clockid_t id, ktime_t *kt)
+{
+	struct tk_data *aux_tkd = aux_get_tk_data(id);
+	struct timekeeper *aux_tk;
+	unsigned int seq;
+	ktime_t base;
+	u64 nsecs;
+
+	WARN_ON(timekeeping_suspended);
+
+	if (!aux_tkd)
+		return false;
+
+	aux_tk = &aux_tkd->timekeeper;
+	do {
+		seq = read_seqcount_begin(&aux_tkd->seq);
+		if (!aux_tk->clock_valid)
+			return false;
+
+		base = ktime_add(aux_tk->tkr_mono.base, aux_tk->offs_aux);
+		nsecs = timekeeping_get_ns(&aux_tk->tkr_mono);
+	} while (read_seqcount_retry(&aux_tkd->seq, seq));
+
+	*kt = ktime_add_ns(base, nsecs);
+	return true;
+}
+EXPORT_SYMBOL_GPL(ktime_get_aux);
+
+/**
+ * ktime_get_aux_ts64 - Get time for a AUX clock
+ * @id:	ID of the clock to read (CLOCK_AUX...)
+ * @ts:	Pointer to timespec64 to store the time stamp
+ *
+ * Returns: True if the timestamp is valid, false otherwise
+ */
+bool ktime_get_aux_ts64(clockid_t id, struct timespec64 *ts)
+{
+	ktime_t now;
+
+	if (!ktime_get_aux(id, &now))
+		return false;
+	*ts = ktime_to_timespec64(now);
+	return true;
+}
+EXPORT_SYMBOL_GPL(ktime_get_aux_ts64);
+
+static int aux_get_res(clockid_t id, struct timespec64 *tp)
+{
+	if (!clockid_aux_valid(id))
+		return -ENODEV;
+
+	tp->tv_sec = aux_clock_resolution_ns() / NSEC_PER_SEC;
+	tp->tv_nsec = aux_clock_resolution_ns() % NSEC_PER_SEC;
+	return 0;
+}
+
+static int aux_get_timespec(clockid_t id, struct timespec64 *tp)
+{
+	return ktime_get_aux_ts64(id, tp) ? 0 : -ENODEV;
+}
+
+static int aux_clock_set(const clockid_t id, const struct timespec64 *tnew)
+{
+	struct tk_data *aux_tkd = aux_get_tk_data(id);
+	struct timekeeper *aux_tks;
+	ktime_t tnow, nsecs;
+
+	if (!timespec64_valid_settod(tnew))
+		return -EINVAL;
+	if (!aux_tkd)
+		return -ENODEV;
+
+	aux_tks = &aux_tkd->shadow_timekeeper;
+
+	guard(raw_spinlock_irq)(&aux_tkd->lock);
+	if (!aux_tks->clock_valid)
+		return -ENODEV;
+
+	/* Forward the timekeeper base time */
+	timekeeping_forward_now(aux_tks);
+	/*
+	 * Get the updated base time. tkr_mono.base has not been
+	 * updated yet, so do that first. That makes the update
+	 * in timekeeping_update_from_shadow() redundant, but
+	 * that's harmless. After that @tnow can be calculated
+	 * by using tkr_mono::cycle_last, which has been set
+	 * by timekeeping_forward_now().
+	 */
+	tk_update_ktime_data(aux_tks);
+	nsecs = timekeeping_cycles_to_ns(&aux_tks->tkr_mono, aux_tks->tkr_mono.cycle_last);
+	tnow = ktime_add(aux_tks->tkr_mono.base, nsecs);
+
+	/*
+	 * Calculate the new AUX offset as delta to @tnow ("monotonic").
+	 * That avoids all the tk::xtime back and forth conversions as
+	 * xtime ("realtime") is not applicable for auxiliary clocks and
+	 * kept in sync with "monotonic".
+	 */
+	aux_tks->offs_aux = ktime_sub(timespec64_to_ktime(*tnew), tnow);
+
+	timekeeping_update_from_shadow(aux_tkd, TK_UPDATE_ALL);
+	return 0;
+}
+
+static int aux_clock_adj(const clockid_t id, struct __kernel_timex *txc)
+{
+	struct tk_data *aux_tkd = aux_get_tk_data(id);
+	struct adjtimex_result result = { };
+
+	if (!aux_tkd)
+		return -ENODEV;
+
+	/*
+	 * @result is ignored for now as there are neither hrtimers nor a
+	 * RTC related to auxiliary clocks for now.
+	 */
+	return __do_adjtimex(aux_tkd, txc, &result);
+}
+
+const struct k_clock clock_aux = {
+	.clock_getres		= aux_get_res,
+	.clock_get_timespec	= aux_get_timespec,
+	.clock_set		= aux_clock_set,
+	.clock_adj		= aux_clock_adj,
+};
+
+static void aux_clock_enable(clockid_t id)
+{
+	struct tk_read_base *tkr_raw = &tk_core.timekeeper.tkr_raw;
+	struct tk_data *aux_tkd = aux_get_tk_data(id);
+	struct timekeeper *aux_tks = &aux_tkd->shadow_timekeeper;
+
+	/* Prevent the core timekeeper from changing. */
+	guard(raw_spinlock_irq)(&tk_core.lock);
+
+	/*
+	 * Setup the auxiliary clock assuming that the raw core timekeeper
+	 * clock frequency conversion is close enough. Userspace has to
+	 * adjust for the deviation via clock_adjtime(2).
+	 */
+	guard(raw_spinlock_nested)(&aux_tkd->lock);
+
+	/* Remove leftovers of a previous registration */
+	memset(aux_tks, 0, sizeof(*aux_tks));
+	/* Restore the timekeeper id */
+	aux_tks->id = aux_tkd->timekeeper.id;
+	/* Setup the timekeeper based on the current system clocksource */
+	tk_setup_internals(aux_tks, tkr_raw->clock);
+
+	/* Mark it valid and set it live */
+	aux_tks->clock_valid = true;
+	timekeeping_update_from_shadow(aux_tkd, TK_UPDATE_ALL);
+}
+
+static void aux_clock_disable(clockid_t id)
+{
+	struct tk_data *aux_tkd = aux_get_tk_data(id);
+
+	guard(raw_spinlock_irq)(&aux_tkd->lock);
+	aux_tkd->shadow_timekeeper.clock_valid = false;
+	timekeeping_update_from_shadow(aux_tkd, TK_UPDATE_ALL);
+}
+
+static DEFINE_MUTEX(aux_clock_mutex);
+
+static ssize_t aux_clock_enable_store(struct kobject *kobj, struct kobj_attribute *attr,
+				      const char *buf, size_t count)
+{
+	/* Lazy atoi() as name is "0..7" */
+	int id = kobj->name[0] & 0x7;
+	bool enable;
+
+	if (!capable(CAP_SYS_TIME))
+		return -EPERM;
+
+	if (kstrtobool(buf, &enable) < 0)
+		return -EINVAL;
+
+	guard(mutex)(&aux_clock_mutex);
+	if (enable == test_bit(id, &aux_timekeepers))
+		return count;
+
+	if (enable) {
+		aux_clock_enable(CLOCK_AUX + id);
+		set_bit(id, &aux_timekeepers);
+	} else {
+		aux_clock_disable(CLOCK_AUX + id);
+		clear_bit(id, &aux_timekeepers);
+	}
+	return count;
+}
+
+static ssize_t aux_clock_enable_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	unsigned long active = READ_ONCE(aux_timekeepers);
+	/* Lazy atoi() as name is "0..7" */
+	int id = kobj->name[0] & 0x7;
+
+	return sysfs_emit(buf, "%d\n", test_bit(id, &active));
+}
+
+static struct kobj_attribute aux_clock_enable_attr = __ATTR_RW(aux_clock_enable);
+
+static struct attribute *aux_clock_enable_attrs[] = {
+	&aux_clock_enable_attr.attr,
+	NULL
+};
+
+static const struct attribute_group aux_clock_enable_attr_group = {
+	.attrs = aux_clock_enable_attrs,
+};
+
+static int __init tk_aux_sysfs_init(void)
+{
+	struct kobject *auxo, *tko = kobject_create_and_add("time", kernel_kobj);
+
+	if (!tko)
+		return -ENOMEM;
+
+	auxo = kobject_create_and_add("aux_clocks", tko);
+	if (!auxo) {
+		kobject_put(tko);
+		return -ENOMEM;
+	}
+
+	for (int i = 0; i <= MAX_AUX_CLOCKS; i++) {
+		char id[2] = { [0] = '0' + i, };
+		struct kobject *clk = kobject_create_and_add(id, auxo);
+
+		if (!clk)
+			return -ENOMEM;
+
+		int ret = sysfs_create_group(clk, &aux_clock_enable_attr_group);
+
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+late_initcall(tk_aux_sysfs_init);
+
+static __init void tk_aux_setup(void)
+{
+	for (int i = TIMEKEEPER_AUX_FIRST; i <= TIMEKEEPER_AUX_LAST; i++)
+		tkd_basic_setup(&timekeeper_data[i], i, false);
+}
+#endif /* CONFIG_POSIX_AUX_CLOCKS */