299 lines
7.3 KiB
C
Executable file
299 lines
7.3 KiB
C
Executable file
/* 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 <asm/mshyperv.h>
|
|
#include <linux/compat_time.h>
|
|
|
|
#define __vdso_data (VVAR(_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_TSCPAGE
|
|
extern struct ms_hyperv_tsc_page hvclock_page
|
|
__attribute__((visibility("hidden")));
|
|
#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
|
|
|
|
#define VDSO_HAS_32BIT_FALLBACK 1
|
|
|
|
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_gettime), [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), [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_TSCPAGE
|
|
static u64 vread_hvclock(void)
|
|
{
|
|
return hv_read_tsc_page(&hvclock_page);
|
|
}
|
|
#endif
|
|
|
|
static inline u64 __arch_get_hw_counter(s32 clock_mode)
|
|
{
|
|
if (clock_mode == VCLOCK_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 == VCLOCK_PVCLOCK) {
|
|
barrier();
|
|
return vread_pvclock();
|
|
}
|
|
#endif
|
|
#ifdef CONFIG_HYPERV_TSCPAGE
|
|
if (clock_mode == VCLOCK_HVCLOCK) {
|
|
barrier();
|
|
return vread_hvclock();
|
|
}
|
|
#endif
|
|
return U64_MAX;
|
|
}
|
|
|
|
static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
|
|
{
|
|
return __vdso_data;
|
|
}
|
|
|
|
/*
|
|
* 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 */
|