linux/arch/x86/include/asm/vdso/gettimeofday.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Fast user context implementation of clock_gettime, gettimeofday, and time.
 *
 * Copyright (C) 2019 ARM Limited.
 * Copyright 2006 Andi Kleen, SUSE Labs.
 * 32 Bit compat layer by Stefani Seibold <[email protected]>
 *  sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
 */
#ifndef __ASM_VDSO_GETTIMEOFDAY_H
#define __ASM_VDSO_GETTIMEOFDAY_H

#ifndef __ASSEMBLY__

#include <uapi/linux/time.h>
#include <asm/vgtod.h>
#include <asm/vvar.h>
#include <asm/unistd.h>
#include <asm/msr.h>
#include <asm/pvclock.h>
#include <clocksource/hyperv_timer.h>

#define __vdso_data …
#define __timens_vdso_data …

#define VDSO_HAS_TIME …

#define VDSO_HAS_CLOCK_GETRES …

/*
 * Declare the memory-mapped vclock data pages.  These come from hypervisors.
 * If we ever reintroduce something like direct access to an MMIO clock like
 * the HPET again, it will go here as well.
 *
 * A load from any of these pages will segfault if the clock in question is
 * disabled, so appropriate compiler barriers and checks need to be used
 * to prevent stray loads.
 *
 * These declarations MUST NOT be const.  The compiler will assume that
 * an extern const variable has genuinely constant contents, and the
 * resulting code won't work, since the whole point is that these pages
 * change over time, possibly while we're accessing them.
 */

#ifdef CONFIG_PARAVIRT_CLOCK
/*
 * This is the vCPU 0 pvclock page.  We only use pvclock from the vDSO
 * if the hypervisor tells us that all vCPUs can get valid data from the
 * vCPU 0 page.
 */
extern struct pvclock_vsyscall_time_info pvclock_page
	__attribute__((hidden));
#endif

#ifdef CONFIG_HYPERV_TIMER
extern struct ms_hyperv_tsc_page hvclock_page
	__attribute__((hidden));
#endif

#ifdef CONFIG_TIME_NS
static __always_inline
const struct vdso_data *__arch_get_timens_vdso_data(const struct vdso_data *vd)
{ … }
#endif

#ifndef BUILD_VDSO32

static __always_inline
long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
{
	long ret;

	asm ("syscall" : "=a" (ret), "=m" (*_ts) :
	     "0" (__NR_clock_gettime), "D" (_clkid), "S" (_ts) :
	     "rcx", "r11");

	return ret;
}

static __always_inline
long gettimeofday_fallback(struct __kernel_old_timeval *_tv,
			   struct timezone *_tz)
{
	long ret;

	asm("syscall" : "=a" (ret) :
	    "0" (__NR_gettimeofday), "D" (_tv), "S" (_tz) : "memory");

	return ret;
}

static __always_inline
long clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
{
	long ret;

	asm ("syscall" : "=a" (ret), "=m" (*_ts) :
	     "0" (__NR_clock_getres), "D" (_clkid), "S" (_ts) :
	     "rcx", "r11");

	return ret;
}

#else

static __always_inline
long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
{ … }

static __always_inline
long clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
{ … }

static __always_inline
long gettimeofday_fallback(struct __kernel_old_timeval *_tv,
			   struct timezone *_tz)
{ … }

static __always_inline long
clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
{ … }

static __always_inline
long clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
{ … }

#endif

#ifdef CONFIG_PARAVIRT_CLOCK
static u64 vread_pvclock(void)
{ … }
#endif

#ifdef CONFIG_HYPERV_TIMER
static u64 vread_hvclock(void)
{ … }
#endif

static inline u64 __arch_get_hw_counter(s32 clock_mode,
					const struct vdso_data *vd)
{ … }

static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
{ … }

static inline bool arch_vdso_clocksource_ok(const struct vdso_data *vd)
{ … }
#define vdso_clocksource_ok …

/*
 * Clocksource read value validation to handle PV and HyperV clocksources
 * which can be invalidated asynchronously and indicate invalidation by
 * returning U64_MAX, which can be effectively tested by checking for a
 * negative value after casting it to s64.
 *
 * This effectively forces a S64_MAX mask on the calculations, unlike the
 * U64_MAX mask normally used by x86 clocksources.
 */
static inline bool arch_vdso_cycles_ok(u64 cycles)
{ … }
#define vdso_cycles_ok …

/*
 * x86 specific calculation of nanoseconds for the current cycle count
 *
 * The regular implementation assumes that clocksource reads are globally
 * monotonic. The TSC can be slightly off across sockets which can cause
 * the regular delta calculation (@cycles - @last) to return a huge time
 * jump.
 *
 * Therefore it needs to be verified that @cycles are greater than
 * @vd->cycles_last. If not then use @vd->cycles_last, which is the base
 * time of the current conversion period.
 *
 * This variant also uses a custom mask because while the clocksource mask of
 * all the VDSO capable clocksources on x86 is U64_MAX, the above code uses
 * U64_MASK as an exception value, additionally arch_vdso_cycles_ok() above
 * declares everything with the MSB/Sign-bit set as invalid. Therefore the
 * effective mask is S64_MAX.
 */
static __always_inline u64 vdso_calc_ns(const struct vdso_data *vd, u64 cycles, u64 base)
{ … }
#define vdso_calc_ns …

#endif /* !__ASSEMBLY__ */

#endif /* __ASM_VDSO_GETTIMEOFDAY_H */