Commit cd3557a7 authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Thomas Gleixner
Browse files

vdso/gettimeofday: Add support for auxiliary clocks 



Expose the auxiliary clocks through the vDSO.

Architectures not using the generic vDSO time framework,
namely SPARC64, are not supported.

Signed-off-by: default avatarThomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250701-vdso-auxclock-v1-12-df7d9f87b9b8@linutronix.de
parent 380b84e1

include/vdso/datapage.h

+2 −0
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
#ifndef __ASSEMBLY__



#include <linux/compiler.h>

#include <uapi/linux/bits.h>

#include <uapi/linux/time.h>

#include <uapi/linux/types.h>

#include <uapi/asm-generic/errno-base.h>
@@ -46,6 +47,7 @@ struct vdso_arch_data { 
#define VDSO_COARSE	(BIT(CLOCK_REALTIME_COARSE)	| \

			 BIT(CLOCK_MONOTONIC_COARSE))

#define VDSO_RAW	(BIT(CLOCK_MONOTONIC_RAW))

#define VDSO_AUX	__GENMASK(CLOCK_AUX_LAST, CLOCK_AUX)



#define CS_HRES_COARSE	0

#define CS_RAW		1

lib/vdso/gettimeofday.c

+48 −1
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
/*

 * Generic userspace implementations of gettimeofday() and similar.

 */

#include <vdso/auxclock.h>

#include <vdso/datapage.h>

#include <vdso/helpers.h>
@@ -74,7 +75,7 @@ static inline bool vdso_cycles_ok(u64 cycles) 
static __always_inline bool vdso_clockid_valid(clockid_t clock)

{

	/* Check for negative values or invalid clocks */

	return likely((u32) clock < MAX_CLOCKS);

	return likely((u32) clock <= CLOCK_AUX_LAST);

}



/*
@@ -268,6 +269,48 @@ bool do_coarse(const struct vdso_time_data *vd, const struct vdso_clock *vc, 
	return true;

}



static __always_inline

bool do_aux(const struct vdso_time_data *vd, clockid_t clock, struct __kernel_timespec *ts)

{

	const struct vdso_clock *vc;

	u32 seq, idx;

	u64 sec, ns;



	if (!IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS))

		return false;



	idx = clock - CLOCK_AUX;

	vc = &vd->aux_clock_data[idx];



	do {

		/*

		 * Open coded function vdso_read_begin() to handle

		 * VDSO_CLOCK_TIMENS. See comment in do_hres().

		 */

		while ((seq = READ_ONCE(vc->seq)) & 1) {

			if (IS_ENABLED(CONFIG_TIME_NS) && vc->clock_mode == VDSO_CLOCKMODE_TIMENS) {

				vd = __arch_get_vdso_u_timens_data(vd);

				vc = &vd->aux_clock_data[idx];

				/* Re-read from the real time data page */

				continue;

			}

			cpu_relax();

		}

		smp_rmb();



		/* Auxclock disabled? */

		if (vc->clock_mode == VDSO_CLOCKMODE_NONE)

			return false;



		if (!vdso_get_timestamp(vd, vc, VDSO_BASE_AUX, &sec, &ns))

			return false;

	} while (unlikely(vdso_read_retry(vc, seq)));



	vdso_set_timespec(ts, sec, ns);



	return true;

}



static __always_inline bool

__cvdso_clock_gettime_common(const struct vdso_time_data *vd, clockid_t clock,

			     struct __kernel_timespec *ts)
@@ -289,6 +332,8 @@ __cvdso_clock_gettime_common(const struct vdso_time_data *vd, clockid_t clock, 
		return do_coarse(vd, &vc[CS_HRES_COARSE], clock, ts);

	else if (msk & VDSO_RAW)

		vc = &vc[CS_RAW];

	else if (msk & VDSO_AUX)

		return do_aux(vd, clock, ts);

	else

		return false;
@@ -433,6 +478,8 @@ bool __cvdso_clock_getres_common(const struct vdso_time_data *vd, clockid_t cloc 
		 * Preserves the behaviour of posix_get_coarse_res().

		 */

		ns = LOW_RES_NSEC;

	} else if (msk & VDSO_AUX) {

		ns = aux_clock_resolution_ns();

	} else {

		return false;

	}