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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /arch/x86/include/asm/vdso/gettimeofday.h
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/x86/include/asm/vdso/gettimeofday.h')
-rw-r--r--arch/x86/include/asm/vdso/gettimeofday.h323
1 files changed, 323 insertions, 0 deletions
diff --git a/arch/x86/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h
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+++ b/arch/x86/include/asm/vdso/gettimeofday.h
@@ -0,0 +1,323 @@
+/* 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(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 */