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vdso/gettimeofday: Add support for auxiliary clocks

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Expose the auxiliary clocks through the vDSO.

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

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250701-vdso-auxclock-v1-12-df7d9f87b9b8@linutronix.de
This commit is contained in:
Thomas Weißschuh 2025-07-01 10:58:06 +02:00 • committed by Thomas Gleixner
parent 380b84e168
commit cd3557a761
2 changed files with 50 additions and 1 deletions
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2
include/vdso/datapage.h
View file

@ -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

49
lib/vdso/gettimeofday.c
View file

@ -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;
}