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/* 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 (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(const struct vdso_data *vd)
{
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,
const struct vdso_data *vd)
{
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 */
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