arch/x86/include/asm/vdso/gettimeofday.h - linux/kernel/git/gregkh/usb - Git at Google

 /* 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 <stefani@seibold.net>
  *  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 (VVAR(_vdso_data))
 #define __timens_vdso_data (TIMENS(_vdso_data))

 #define VDSO_HAS_TIME 1

 #define VDSO_HAS_CLOCK_GETRES 1

 /*
  * 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__((visibility("hidden")));
 #endif

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

 #ifdef CONFIG_TIME_NS
 static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void)
 {
 	return __timens_vdso_data;
 }
 #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)
 {
 	long ret;

 	asm (
 		"mov %%ebx, %%edx \n"
 		"mov %[clock], %%ebx \n"
 		"call __kernel_vsyscall \n"
 		"mov %%edx, %%ebx \n"
 		: "=a" (ret), "=m" (*_ts)
 		: "0" (__NR_clock_gettime64), [clock] "g" (_clkid), "c" (_ts)
 		: "edx");

 	return ret;
 }

 static __always_inline
 long clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
 {
 	long ret;

 	asm (
 		"mov %%ebx, %%edx \n"
 		"mov %[clock], %%ebx \n"
 		"call __kernel_vsyscall \n"
 		"mov %%edx, %%ebx \n"
 		: "=a" (ret), "=m" (*_ts)
 		: "0" (__NR_clock_gettime), [clock] "g" (_clkid), "c" (_ts)
 		: "edx");

 	return ret;
 }

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

 	asm(
 		"mov %%ebx, %%edx \n"
 		"mov %2, %%ebx \n"
 		"call __kernel_vsyscall \n"
 		"mov %%edx, %%ebx \n"
 		: "=a" (ret)
 		: "0" (__NR_gettimeofday), "g" (_tv), "c" (_tz)
 		: "memory", "edx");

 	return ret;
 }

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

 	asm (
 		"mov %%ebx, %%edx \n"
 		"mov %[clock], %%ebx \n"
 		"call __kernel_vsyscall \n"
 		"mov %%edx, %%ebx \n"
 		: "=a" (ret), "=m" (*_ts)
 		: "0" (__NR_clock_getres_time64), [clock] "g" (_clkid), "c" (_ts)
 		: "edx");

 	return ret;
 }

 static __always_inline
 long clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
 {
 	long ret;

 	asm (
 		"mov %%ebx, %%edx \n"
 		"mov %[clock], %%ebx \n"
 		"call __kernel_vsyscall \n"
 		"mov %%edx, %%ebx \n"
 		: "=a" (ret), "=m" (*_ts)
 		: "0" (__NR_clock_getres), [clock] "g" (_clkid), "c" (_ts)
 		: "edx");

 	return ret;
 }

 #endif

 #ifdef CONFIG_PARAVIRT_CLOCK
 static u64 vread_pvclock(void)
 {
 	const struct pvclock_vcpu_time_info *pvti = &pvclock_page.pvti;
 	u32 version;
 	u64 ret;

 	/*
 	 * Note: The kernel and hypervisor must guarantee that cpu ID
 	 * number maps 1:1 to per-CPU pvclock time info.
 	 *
 	 * Because the hypervisor is entirely unaware of guest userspace
 	 * preemption, it cannot guarantee that per-CPU pvclock time
 	 * info is updated if the underlying CPU changes or that that
 	 * version is increased whenever underlying CPU changes.
 	 *
 	 * On KVM, we are guaranteed that pvti updates for any vCPU are
 	 * atomic as seen by *all* vCPUs.  This is an even stronger
 	 * guarantee than we get with a normal seqlock.
 	 *
 	 * On Xen, we don't appear to have that guarantee, but Xen still
 	 * supplies a valid seqlock using the version field.
 	 *
 	 * We only do pvclock vdso timing at all if
 	 * PVCLOCK_TSC_STABLE_BIT is set, and we interpret that bit to
 	 * mean that all vCPUs have matching pvti and that the TSC is
 	 * synced, so we can just look at vCPU 0's pvti.
 	 */

 	do {
 		version = pvclock_read_begin(pvti);

 		if (unlikely(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT)))
 			return U64_MAX;

 		ret = __pvclock_read_cycles(pvti, rdtsc_ordered());
 	} while (pvclock_read_retry(pvti, version));

 	return ret;
 }
 #endif

 #ifdef CONFIG_HYPERV_TIMER
 static u64 vread_hvclock(void)
 {
 	return hv_read_tsc_page(&hvclock_page);
 }
 #endif

 static inline u64 __arch_get_hw_counter(s32 clock_mode)
 {
 	if (likely(clock_mode == VDSO_CLOCKMODE_TSC))
 		return (u64)rdtsc_ordered();
 	/*
 	 * For any memory-mapped vclock type, we need to make sure that gcc
 	 * doesn't cleverly hoist a load before the mode check.  Otherwise we
 	 * might end up touching the memory-mapped page even if the vclock in
 	 * question isn't enabled, which will segfault.  Hence the barriers.
 	 */
 #ifdef CONFIG_PARAVIRT_CLOCK
 	if (clock_mode == VDSO_CLOCKMODE_PVCLOCK) {
 		barrier();
 		return vread_pvclock();
 	}
 #endif
 #ifdef CONFIG_HYPERV_TIMER
 	if (clock_mode == VDSO_CLOCKMODE_HVCLOCK) {
 		barrier();
 		return vread_hvclock();
 	}
 #endif
 	return U64_MAX;
 }

 static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
 {
 	return __vdso_data;
 }

 static inline bool arch_vdso_clocksource_ok(const struct vdso_data *vd)
 {
 	return true;
 }
 #define vdso_clocksource_ok arch_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.
  */
 static inline bool arch_vdso_cycles_ok(u64 cycles)
 {
 	return (s64)cycles >= 0;
 }
 #define vdso_cycles_ok arch_vdso_cycles_ok

 /*
  * x86 specific delta calculation.
  *
  * 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
  * @last. If not then use @last, which is the base time of the current
  * conversion period.
  *
  * This variant also removes the masking of the subtraction because the
  * clocksource mask of all VDSO capable clocksources on x86 is U64_MAX
  * which would result in a pointless operation. The compiler cannot
  * optimize it away as the mask comes from the vdso data and is not compile
  * time constant.
  */
 static __always_inline
 u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
 {
 	if (cycles > last)
 		return (cycles - last) * mult;
 	return 0;
 }
 #define vdso_calc_delta vdso_calc_delta

 #endif /* !__ASSEMBLY__ */

 #endif /* __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 <stefani@seibold.net>
	* 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 (VVAR(_vdso_data))
	#define __timens_vdso_data (TIMENS(_vdso_data))

	#define VDSO_HAS_TIME 1

	#define VDSO_HAS_CLOCK_GETRES 1

	/*
	* 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__((visibility("hidden")));
	#endif

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

	#ifdef CONFIG_TIME_NS
	static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void)
	{
	return __timens_vdso_data;
	}
	#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)
	{
	long ret;

	asm (
	"mov %%ebx, %%edx \n"
	"mov %[clock], %%ebx \n"
	"call __kernel_vsyscall \n"
	"mov %%edx, %%ebx \n"
	: "=a" (ret), "=m" (*_ts)
	: "0" (__NR_clock_gettime64), [clock] "g" (_clkid), "c" (_ts)
	: "edx");

	return ret;
	}

	static __always_inline
	long clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
	{
	long ret;

	asm (
	"mov %%ebx, %%edx \n"
	"mov %[clock], %%ebx \n"
	"call __kernel_vsyscall \n"
	"mov %%edx, %%ebx \n"
	: "=a" (ret), "=m" (*_ts)
	: "0" (__NR_clock_gettime), [clock] "g" (_clkid), "c" (_ts)
	: "edx");

	return ret;
	}

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

	asm(
	"mov %%ebx, %%edx \n"
	"mov %2, %%ebx \n"
	"call __kernel_vsyscall \n"
	"mov %%edx, %%ebx \n"
	: "=a" (ret)
	: "0" (__NR_gettimeofday), "g" (_tv), "c" (_tz)
	: "memory", "edx");

	return ret;
	}

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

	asm (
	"mov %%ebx, %%edx \n"
	"mov %[clock], %%ebx \n"
	"call __kernel_vsyscall \n"
	"mov %%edx, %%ebx \n"
	: "=a" (ret), "=m" (*_ts)
	: "0" (__NR_clock_getres_time64), [clock] "g" (_clkid), "c" (_ts)
	: "edx");

	return ret;
	}

	static __always_inline
	long clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
	{
	long ret;

	asm (
	"mov %%ebx, %%edx \n"
	"mov %[clock], %%ebx \n"
	"call __kernel_vsyscall \n"
	"mov %%edx, %%ebx \n"
	: "=a" (ret), "=m" (*_ts)
	: "0" (__NR_clock_getres), [clock] "g" (_clkid), "c" (_ts)
	: "edx");

	return ret;
	}

	#endif

	#ifdef CONFIG_PARAVIRT_CLOCK
	static u64 vread_pvclock(void)
	{
	const struct pvclock_vcpu_time_info *pvti = &pvclock_page.pvti;
	u32 version;
	u64 ret;

	/*
	* Note: The kernel and hypervisor must guarantee that cpu ID
	* number maps 1:1 to per-CPU pvclock time info.
	*
	* Because the hypervisor is entirely unaware of guest userspace
	* preemption, it cannot guarantee that per-CPU pvclock time
	* info is updated if the underlying CPU changes or that that
	* version is increased whenever underlying CPU changes.
	*
	* On KVM, we are guaranteed that pvti updates for any vCPU are
	* atomic as seen by all vCPUs. This is an even stronger
	* guarantee than we get with a normal seqlock.
	*
	* On Xen, we don't appear to have that guarantee, but Xen still
	* supplies a valid seqlock using the version field.
	*
	* We only do pvclock vdso timing at all if
	* PVCLOCK_TSC_STABLE_BIT is set, and we interpret that bit to
	* mean that all vCPUs have matching pvti and that the TSC is
	* synced, so we can just look at vCPU 0's pvti.
	*/

	do {
	version = pvclock_read_begin(pvti);

	if (unlikely(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT)))
	return U64_MAX;

	ret = __pvclock_read_cycles(pvti, rdtsc_ordered());
	} while (pvclock_read_retry(pvti, version));

	return ret;
	}
	#endif

	#ifdef CONFIG_HYPERV_TIMER
	static u64 vread_hvclock(void)
	{
	return hv_read_tsc_page(&hvclock_page);
	}
	#endif

	static inline u64 __arch_get_hw_counter(s32 clock_mode)
	{
	if (likely(clock_mode == VDSO_CLOCKMODE_TSC))
	return (u64)rdtsc_ordered();
	/*
	* For any memory-mapped vclock type, we need to make sure that gcc
	* doesn't cleverly hoist a load before the mode check. Otherwise we
	* might end up touching the memory-mapped page even if the vclock in
	* question isn't enabled, which will segfault. Hence the barriers.
	*/
	#ifdef CONFIG_PARAVIRT_CLOCK
	if (clock_mode == VDSO_CLOCKMODE_PVCLOCK) {
	barrier();
	return vread_pvclock();
	}
	#endif
	#ifdef CONFIG_HYPERV_TIMER
	if (clock_mode == VDSO_CLOCKMODE_HVCLOCK) {
	barrier();
	return vread_hvclock();
	}
	#endif
	return U64_MAX;
	}

	static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
	{
	return __vdso_data;
	}

	static inline bool arch_vdso_clocksource_ok(const struct vdso_data *vd)
	{
	return true;
	}
	#define vdso_clocksource_ok arch_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.
	*/
	static inline bool arch_vdso_cycles_ok(u64 cycles)
	{
	return (s64)cycles >= 0;
	}
	#define vdso_cycles_ok arch_vdso_cycles_ok

	/*
	* x86 specific delta calculation.
	*
	* 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
	* @last. If not then use @last, which is the base time of the current
	* conversion period.
	*
	* This variant also removes the masking of the subtraction because the
	* clocksource mask of all VDSO capable clocksources on x86 is U64_MAX
	* which would result in a pointless operation. The compiler cannot
	* optimize it away as the mask comes from the vdso data and is not compile
	* time constant.
	*/
	static __always_inline
	u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
	{
	if (cycles > last)
	return (cycles - last) * mult;
	return 0;
	}
	#define vdso_calc_delta vdso_calc_delta

	#endif /* !__ASSEMBLY__ */

	#endif /* __ASM_VDSO_GETTIMEOFDAY_H */