Re: [PATCH v7 04/25] arm64: Substitute gettimeofday with C implementation

[Vincenzo Frascino <vincenzo.frascino@arm.com>]

Hi Marek,

On 6/28/19 2:09 PM, Marek Szyprowski wrote:
> Dear All,
> 
> On 2019-06-21 11:52, Vincenzo Frascino wrote:
>> To take advantage of the commonly defined vdso interface for
>> gettimeofday the architectural code requires an adaptation.
>>
>> Re-implement the gettimeofday vdso in C in order to use lib/vdso.
>>
>> With the new implementation arm64 gains support for CLOCK_BOOTTIME
>> and CLOCK_TAI.
>>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will.deacon@arm.com>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> Tested-by: Shijith Thotton <sthotton@marvell.com>
>> Tested-by: Andre Przywara <andre.przywara@arm.com>
>> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> 
> This patch causes serious regression on Samsung Exynos5433 SoC based 
> TM2(e) boards. The time in userspace is always set to begin of the epoch:
> 
> # date 062813152019
> Fri Jun 28 13:15:00 UTC 2019
> # date
> Thu Jan  1 00:00:00 UTC 1970
> # date
> Thu Jan  1 00:00:00 UTC 1970
> 
> I've noticed that since the patch landed in Linux next-20190625 and 
> bisect indeed pointed to this patch.
> 

Thank you for reporting this, seems that the next that you posted is missing
some fixes for arm64.

Could you please try the tree below?

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/vdso

Let us know if the functionality is restored. Otherwise the issue will require
further investigation.

>> ---
>>   arch/arm64/Kconfig                         |   2 +
>>   arch/arm64/include/asm/vdso/gettimeofday.h |  86 ++++++
>>   arch/arm64/include/asm/vdso/vsyscall.h     |  53 ++++
>>   arch/arm64/include/asm/vdso_datapage.h     |  48 ---
>>   arch/arm64/kernel/asm-offsets.c            |  33 +-
>>   arch/arm64/kernel/vdso.c                   |  51 +---
>>   arch/arm64/kernel/vdso/Makefile            |  34 ++-
>>   arch/arm64/kernel/vdso/gettimeofday.S      | 334 ---------------------
>>   arch/arm64/kernel/vdso/vgettimeofday.c     |  28 ++
>>   9 files changed, 223 insertions(+), 446 deletions(-)
>>   create mode 100644 arch/arm64/include/asm/vdso/gettimeofday.h
>>   create mode 100644 arch/arm64/include/asm/vdso/vsyscall.h
>>   delete mode 100644 arch/arm64/include/asm/vdso_datapage.h
>>   delete mode 100644 arch/arm64/kernel/vdso/gettimeofday.S
>>   create mode 100644 arch/arm64/kernel/vdso/vgettimeofday.c
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 697ea0510729..952c9f8cf3b8 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -107,6 +107,7 @@ config ARM64
>>   	select GENERIC_STRNCPY_FROM_USER
>>   	select GENERIC_STRNLEN_USER
>>   	select GENERIC_TIME_VSYSCALL
>> +	select GENERIC_GETTIMEOFDAY
>>   	select HANDLE_DOMAIN_IRQ
>>   	select HARDIRQS_SW_RESEND
>>   	select HAVE_PCI
>> @@ -160,6 +161,7 @@ config ARM64
>>   	select HAVE_SYSCALL_TRACEPOINTS
>>   	select HAVE_KPROBES
>>   	select HAVE_KRETPROBES
>> +	select HAVE_GENERIC_VDSO
>>   	select IOMMU_DMA if IOMMU_SUPPORT
>>   	select IRQ_DOMAIN
>>   	select IRQ_FORCED_THREADING
>> diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h
>> new file mode 100644
>> index 000000000000..bc3cb6738051
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/vdso/gettimeofday.h
>> @@ -0,0 +1,86 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Copyright (C) 2018 ARM Limited
>> + */
>> +#ifndef __ASM_VDSO_GETTIMEOFDAY_H
>> +#define __ASM_VDSO_GETTIMEOFDAY_H
>> +
>> +#ifndef __ASSEMBLY__
>> +
>> +#include <asm/unistd.h>
>> +#include <uapi/linux/time.h>
>> +
>> +#define VDSO_HAS_CLOCK_GETRES		1
>> +
>> +static __always_inline int gettimeofday_fallback(
>> +					struct __kernel_old_timeval *_tv,
>> +					struct timezone *_tz)
>> +{
>> +	register struct timezone *tz asm("x1") = _tz;
>> +	register struct __kernel_old_timeval *tv asm("x0") = _tv;
>> +	register long ret asm ("x0");
>> +	register long nr asm("x8") = __NR_gettimeofday;
>> +
>> +	asm volatile(
>> +	"       svc #0\n"
>> +	: "=r" (ret)
>> +	: "r" (tv), "r" (tz), "r" (nr)
>> +	: "memory");
>> +
>> +	return ret;
>> +}
>> +
>> +static __always_inline long clock_gettime_fallback(
>> +					clockid_t _clkid,
>> +					struct __kernel_timespec *_ts)
>> +{
>> +	register struct __kernel_timespec *ts asm("x1") = _ts;
>> +	register clockid_t clkid asm("x0") = _clkid;
>> +	register long ret asm ("x0");
>> +	register long nr asm("x8") = __NR_clock_gettime;
>> +
>> +	asm volatile(
>> +	"       svc #0\n"
>> +	: "=r" (ret)
>> +	: "r" (clkid), "r" (ts), "r" (nr)
>> +	: "memory");
>> +
>> +	return ret;
>> +}
>> +
>> +static __always_inline int clock_getres_fallback(
>> +					clockid_t _clkid,
>> +					struct __kernel_timespec *_ts)
>> +{
>> +	register struct __kernel_timespec *ts asm("x1") = _ts;
>> +	register clockid_t clkid asm("x0") = _clkid;
>> +	register long ret asm ("x0");
>> +	register long nr asm("x8") = __NR_clock_getres;
>> +
>> +	asm volatile(
>> +	"       svc #0\n"
>> +	: "=r" (ret)
>> +	: "r" (clkid), "r" (ts), "r" (nr)
>> +	: "memory");
>> +
>> +	return ret;
>> +}
>> +
>> +static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
>> +{
>> +	u64 res;
>> +
>> +	asm volatile("mrs %0, cntvct_el0" : "=r" (res) :: "memory");
>> +
>> +	return res;
>> +}
>> +
>> +static __always_inline
>> +const struct vdso_data *__arch_get_vdso_data(void)
>> +{
>> +	return _vdso_data;
>> +}
>> +
>> +#endif /* !__ASSEMBLY__ */
>> +
>> +#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
>> diff --git a/arch/arm64/include/asm/vdso/vsyscall.h b/arch/arm64/include/asm/vdso/vsyscall.h
>> new file mode 100644
>> index 000000000000..0c731bfc7c8c
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/vdso/vsyscall.h
>> @@ -0,0 +1,53 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef __ASM_VDSO_VSYSCALL_H
>> +#define __ASM_VDSO_VSYSCALL_H
>> +
>> +#ifndef __ASSEMBLY__
>> +
>> +#include <linux/timekeeper_internal.h>
>> +#include <vdso/datapage.h>
>> +
>> +#define VDSO_PRECISION_MASK	~(0xFF00ULL<<48)
>> +
>> +extern struct vdso_data *vdso_data;
>> +
>> +/*
>> + * Update the vDSO data page to keep in sync with kernel timekeeping.
>> + */
>> +static __always_inline
>> +struct vdso_data *__arm64_get_k_vdso_data(void)
>> +{
>> +	return vdso_data;
>> +}
>> +#define __arch_get_k_vdso_data __arm64_get_k_vdso_data
>> +
>> +static __always_inline
>> +int __arm64_get_clock_mode(struct timekeeper *tk)
>> +{
>> +	u32 use_syscall = !tk->tkr_mono.clock->archdata.vdso_direct;
>> +
>> +	return use_syscall;
>> +}
>> +#define __arch_get_clock_mode __arm64_get_clock_mode
>> +
>> +static __always_inline
>> +int __arm64_use_vsyscall(struct vdso_data *vdata)
>> +{
>> +	return !vdata[CS_HRES_COARSE].clock_mode;
>> +}
>> +#define __arch_use_vsyscall __arm64_use_vsyscall
>> +
>> +static __always_inline
>> +void __arm64_update_vsyscall(struct vdso_data *vdata, struct timekeeper *tk)
>> +{
>> +	vdata[CS_HRES_COARSE].mask	= VDSO_PRECISION_MASK;
>> +	vdata[CS_RAW].mask		= VDSO_PRECISION_MASK;
>> +}
>> +#define __arch_update_vsyscall __arm64_update_vsyscall
>> +
>> +/* The asm-generic header needs to be included after the definitions above */
>> +#include <asm-generic/vdso/vsyscall.h>
>> +
>> +#endif /* !__ASSEMBLY__ */
>> +
>> +#endif /* __ASM_VDSO_VSYSCALL_H */
>> diff --git a/arch/arm64/include/asm/vdso_datapage.h b/arch/arm64/include/asm/vdso_datapage.h
>> deleted file mode 100644
>> index f89263c8e11a..000000000000
>> --- a/arch/arm64/include/asm/vdso_datapage.h
>> +++ /dev/null
>> @@ -1,48 +0,0 @@
>> -/*
>> - * Copyright (C) 2012 ARM Limited
>> - *
>> - * This program is free software; you can redistribute it and/or modify
>> - * it under the terms of the GNU General Public License version 2 as
>> - * published by the Free Software Foundation.
>> - *
>> - * This program is distributed in the hope that it will be useful,
>> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> - * GNU General Public License for more details.
>> - *
>> - * You should have received a copy of the GNU General Public License
>> - * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> - */
>> -#ifndef __ASM_VDSO_DATAPAGE_H
>> -#define __ASM_VDSO_DATAPAGE_H
>> -
>> -#ifdef __KERNEL__
>> -
>> -#ifndef __ASSEMBLY__
>> -
>> -struct vdso_data {
>> -	__u64 cs_cycle_last;	/* Timebase at clocksource init */
>> -	__u64 raw_time_sec;	/* Raw time */
>> -	__u64 raw_time_nsec;
>> -	__u64 xtime_clock_sec;	/* Kernel time */
>> -	__u64 xtime_clock_nsec;
>> -	__u64 xtime_coarse_sec;	/* Coarse time */
>> -	__u64 xtime_coarse_nsec;
>> -	__u64 wtm_clock_sec;	/* Wall to monotonic time */
>> -	__u64 wtm_clock_nsec;
>> -	__u32 tb_seq_count;	/* Timebase sequence counter */
>> -	/* cs_* members must be adjacent and in this order (ldp accesses) */
>> -	__u32 cs_mono_mult;	/* NTP-adjusted clocksource multiplier */
>> -	__u32 cs_shift;		/* Clocksource shift (mono = raw) */
>> -	__u32 cs_raw_mult;	/* Raw clocksource multiplier */
>> -	__u32 tz_minuteswest;	/* Whacky timezone stuff */
>> -	__u32 tz_dsttime;
>> -	__u32 use_syscall;
>> -	__u32 hrtimer_res;
>> -};
>> -
>> -#endif /* !__ASSEMBLY__ */
>> -
>> -#endif /* __KERNEL__ */
>> -
>> -#endif /* __ASM_VDSO_DATAPAGE_H */
>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
>> index 947e39896e28..9e4b7ccbab2f 100644
>> --- a/arch/arm64/kernel/asm-offsets.c
>> +++ b/arch/arm64/kernel/asm-offsets.c
>> @@ -25,13 +25,13 @@
>>   #include <linux/kvm_host.h>
>>   #include <linux/preempt.h>
>>   #include <linux/suspend.h>
>> +#include <vdso/datapage.h>
>>   #include <asm/cpufeature.h>
>>   #include <asm/fixmap.h>
>>   #include <asm/thread_info.h>
>>   #include <asm/memory.h>
>>   #include <asm/smp_plat.h>
>>   #include <asm/suspend.h>
>> -#include <asm/vdso_datapage.h>
>>   #include <linux/kbuild.h>
>>   #include <linux/arm-smccc.h>
>>   
>> @@ -100,17 +100,28 @@ int main(void)
>>     DEFINE(CLOCK_COARSE_RES,	LOW_RES_NSEC);
>>     DEFINE(NSEC_PER_SEC,		NSEC_PER_SEC);
>>     BLANK();
>> -  DEFINE(VDSO_CS_CYCLE_LAST,	offsetof(struct vdso_data, cs_cycle_last));
>> -  DEFINE(VDSO_RAW_TIME_SEC,	offsetof(struct vdso_data, raw_time_sec));
>> -  DEFINE(VDSO_XTIME_CLK_SEC,	offsetof(struct vdso_data, xtime_clock_sec));
>> -  DEFINE(VDSO_XTIME_CRS_SEC,	offsetof(struct vdso_data, xtime_coarse_sec));
>> -  DEFINE(VDSO_XTIME_CRS_NSEC,	offsetof(struct vdso_data, xtime_coarse_nsec));
>> -  DEFINE(VDSO_WTM_CLK_SEC,	offsetof(struct vdso_data, wtm_clock_sec));
>> -  DEFINE(VDSO_TB_SEQ_COUNT,	offsetof(struct vdso_data, tb_seq_count));
>> -  DEFINE(VDSO_CS_MONO_MULT,	offsetof(struct vdso_data, cs_mono_mult));
>> -  DEFINE(VDSO_CS_SHIFT,		offsetof(struct vdso_data, cs_shift));
>> +  DEFINE(VDSO_SEQ,		offsetof(struct vdso_data, seq));
>> +  DEFINE(VDSO_CLK_MODE,		offsetof(struct vdso_data, clock_mode));
>> +  DEFINE(VDSO_CYCLE_LAST,	offsetof(struct vdso_data, cycle_last));
>> +  DEFINE(VDSO_MASK,		offsetof(struct vdso_data, mask));
>> +  DEFINE(VDSO_MULT,		offsetof(struct vdso_data, mult));
>> +  DEFINE(VDSO_SHIFT,		offsetof(struct vdso_data, shift));
>> +  DEFINE(VDSO_REALTIME_SEC,	offsetof(struct vdso_data, basetime[CLOCK_REALTIME].sec));
>> +  DEFINE(VDSO_REALTIME_NSEC,	offsetof(struct vdso_data, basetime[CLOCK_REALTIME].nsec));
>> +  DEFINE(VDSO_MONO_SEC,		offsetof(struct vdso_data, basetime[CLOCK_MONOTONIC].sec));
>> +  DEFINE(VDSO_MONO_NSEC,	offsetof(struct vdso_data, basetime[CLOCK_MONOTONIC].nsec));
>> +  DEFINE(VDSO_MONO_RAW_SEC,	offsetof(struct vdso_data, basetime[CLOCK_MONOTONIC_RAW].sec));
>> +  DEFINE(VDSO_MONO_RAW_NSEC,	offsetof(struct vdso_data, basetime[CLOCK_MONOTONIC_RAW].nsec));
>> +  DEFINE(VDSO_BOOTTIME_SEC,	offsetof(struct vdso_data, basetime[CLOCK_BOOTTIME].sec));
>> +  DEFINE(VDSO_BOOTTIME_NSEC,	offsetof(struct vdso_data, basetime[CLOCK_BOOTTIME].nsec));
>> +  DEFINE(VDSO_TAI_SEC,		offsetof(struct vdso_data, basetime[CLOCK_TAI].sec));
>> +  DEFINE(VDSO_TAI_NSEC,		offsetof(struct vdso_data, basetime[CLOCK_TAI].nsec));
>> +  DEFINE(VDSO_RT_COARSE_SEC,	offsetof(struct vdso_data, basetime[CLOCK_REALTIME_COARSE].sec));
>> +  DEFINE(VDSO_RT_COARSE_NSEC,	offsetof(struct vdso_data, basetime[CLOCK_REALTIME_COARSE].nsec));
>> +  DEFINE(VDSO_MONO_COARSE_SEC,	offsetof(struct vdso_data, basetime[CLOCK_MONOTONIC_COARSE].sec));
>> +  DEFINE(VDSO_MONO_COARSE_NSEC,	offsetof(struct vdso_data, basetime[CLOCK_MONOTONIC_COARSE].nsec));
>>     DEFINE(VDSO_TZ_MINWEST,	offsetof(struct vdso_data, tz_minuteswest));
>> -  DEFINE(VDSO_USE_SYSCALL,	offsetof(struct vdso_data, use_syscall));
>> +  DEFINE(VDSO_TZ_DSTTIME,	offsetof(struct vdso_data, tz_dsttime));
>>     BLANK();
>>     DEFINE(TVAL_TV_SEC,		offsetof(struct timeval, tv_sec));
>>     DEFINE(TSPEC_TV_SEC,		offsetof(struct timespec, tv_sec));
>> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
>> index 8074cbd3a3a8..23c38303a52a 100644
>> --- a/arch/arm64/kernel/vdso.c
>> +++ b/arch/arm64/kernel/vdso.c
>> @@ -31,11 +31,13 @@
>>   #include <linux/slab.h>
>>   #include <linux/timekeeper_internal.h>
>>   #include <linux/vmalloc.h>
>> +#include <vdso/datapage.h>
>> +#include <vdso/helpers.h>
>> +#include <vdso/vsyscall.h>
>>   
>>   #include <asm/cacheflush.h>
>>   #include <asm/signal32.h>
>>   #include <asm/vdso.h>
>> -#include <asm/vdso_datapage.h>
>>   
>>   extern char vdso_start[], vdso_end[];
>>   static unsigned long vdso_pages __ro_after_init;
>> @@ -44,10 +46,10 @@ static unsigned long vdso_pages __ro_after_init;
>>    * The vDSO data page.
>>    */
>>   static union {
>> -	struct vdso_data	data;
>> +	struct vdso_data	data[CS_BASES];
>>   	u8			page[PAGE_SIZE];
>>   } vdso_data_store __page_aligned_data;
>> -struct vdso_data *vdso_data = &vdso_data_store.data;
>> +struct vdso_data *vdso_data = vdso_data_store.data;
>>   
>>   #ifdef CONFIG_COMPAT
>>   /*
>> @@ -280,46 +282,3 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
>>   	up_write(&mm->mmap_sem);
>>   	return PTR_ERR(ret);
>>   }
>> -
>> -/*
>> - * Update the vDSO data page to keep in sync with kernel timekeeping.
>> - */
>> -void update_vsyscall(struct timekeeper *tk)
>> -{
>> -	u32 use_syscall = !tk->tkr_mono.clock->archdata.vdso_direct;
>> -
>> -	++vdso_data->tb_seq_count;
>> -	smp_wmb();
>> -
>> -	vdso_data->use_syscall			= use_syscall;
>> -	vdso_data->xtime_coarse_sec		= tk->xtime_sec;
>> -	vdso_data->xtime_coarse_nsec		= tk->tkr_mono.xtime_nsec >>
>> -							tk->tkr_mono.shift;
>> -	vdso_data->wtm_clock_sec		= tk->wall_to_monotonic.tv_sec;
>> -	vdso_data->wtm_clock_nsec		= tk->wall_to_monotonic.tv_nsec;
>> -
>> -	/* Read without the seqlock held by clock_getres() */
>> -	WRITE_ONCE(vdso_data->hrtimer_res, hrtimer_resolution);
>> -
>> -	if (!use_syscall) {
>> -		/* tkr_mono.cycle_last == tkr_raw.cycle_last */
>> -		vdso_data->cs_cycle_last	= tk->tkr_mono.cycle_last;
>> -		vdso_data->raw_time_sec         = tk->raw_sec;
>> -		vdso_data->raw_time_nsec        = tk->tkr_raw.xtime_nsec;
>> -		vdso_data->xtime_clock_sec	= tk->xtime_sec;
>> -		vdso_data->xtime_clock_nsec	= tk->tkr_mono.xtime_nsec;
>> -		vdso_data->cs_mono_mult		= tk->tkr_mono.mult;
>> -		vdso_data->cs_raw_mult		= tk->tkr_raw.mult;
>> -		/* tkr_mono.shift == tkr_raw.shift */
>> -		vdso_data->cs_shift		= tk->tkr_mono.shift;
>> -	}
>> -
>> -	smp_wmb();
>> -	++vdso_data->tb_seq_count;
>> -}
>> -
>> -void update_vsyscall_tz(void)
>> -{
>> -	vdso_data->tz_minuteswest	= sys_tz.tz_minuteswest;
>> -	vdso_data->tz_dsttime		= sys_tz.tz_dsttime;
>> -}
>> diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
>> index fa230ff09aa1..3acfc813e966 100644
>> --- a/arch/arm64/kernel/vdso/Makefile
>> +++ b/arch/arm64/kernel/vdso/Makefile
>> @@ -6,7 +6,12 @@
>>   # Heavily based on the vDSO Makefiles for other archs.
>>   #
>>   
>> -obj-vdso := gettimeofday.o note.o sigreturn.o
>> +# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
>> +# the inclusion of generic Makefile.
>> +ARCH_REL_TYPE_ABS := R_AARCH64_JUMP_SLOT|R_AARCH64_GLOB_DAT|R_AARCH64_ABS64
>> +include $(srctree)/lib/vdso/Makefile
>> +
>> +obj-vdso := vgettimeofday.o note.o sigreturn.o
>>   
>>   # Build rules
>>   targets := $(obj-vdso) vdso.so vdso.so.dbg
>> @@ -15,6 +20,24 @@ obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
>>   ldflags-y := -shared -nostdlib -soname=linux-vdso.so.1 --hash-style=sysv \
>>   		--build-id -n -T
>>   
>> +ccflags-y := -fno-common -fno-builtin -fno-stack-protector
>> +ccflags-y += -DDISABLE_BRANCH_PROFILING
>> +
>> +VDSO_LDFLAGS := -Bsymbolic
>> +
>> +CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os
>> +KBUILD_CFLAGS			+= $(DISABLE_LTO)
>> +KASAN_SANITIZE			:= n
>> +UBSAN_SANITIZE			:= n
>> +OBJECT_FILES_NON_STANDARD	:= y
>> +KCOV_INSTRUMENT			:= n
>> +
>> +ifeq ($(c-gettimeofday-y),)
>> +CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny
>> +else
>> +CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -include $(c-gettimeofday-y)
>> +endif
>> +
>>   # Disable gcov profiling for VDSO code
>>   GCOV_PROFILE := n
>>   
>> @@ -28,6 +51,7 @@ $(obj)/vdso.o : $(obj)/vdso.so
>>   # Link rule for the .so file, .lds has to be first
>>   $(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
>>   	$(call if_changed,ld)
>> +	$(call if_changed,vdso_check)
>>   
>>   # Strip rule for the .so file
>>   $(obj)/%.so: OBJCOPYFLAGS := -S
>> @@ -42,13 +66,9 @@ quiet_cmd_vdsosym = VDSOSYM $@
>>   include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
>>   	$(call if_changed,vdsosym)
>>   
>> -# Assembly rules for the .S files
>> -$(obj-vdso): %.o: %.S FORCE
>> -	$(call if_changed_dep,vdsoas)
>> -
>>   # Actual build commands
>> -quiet_cmd_vdsoas = VDSOA   $@
>> -      cmd_vdsoas = $(CC) $(a_flags) -c -o $@ $<
>> +quiet_cmd_vdsocc = VDSOCC   $@
>> +      cmd_vdsocc = $(CC) $(a_flags) $(c_flags) -c -o $@ $<
>>   
>>   # Install commands for the unstripped file
>>   quiet_cmd_vdso_install = INSTALL $@
>> diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
>> deleted file mode 100644
>> index 856fee6d3512..000000000000
>> --- a/arch/arm64/kernel/vdso/gettimeofday.S
>> +++ /dev/null
>> @@ -1,334 +0,0 @@
>> -/*
>> - * Userspace implementations of gettimeofday() and friends.
>> - *
>> - * Copyright (C) 2012 ARM Limited
>> - *
>> - * This program is free software; you can redistribute it and/or modify
>> - * it under the terms of the GNU General Public License version 2 as
>> - * published by the Free Software Foundation.
>> - *
>> - * This program is distributed in the hope that it will be useful,
>> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> - * GNU General Public License for more details.
>> - *
>> - * You should have received a copy of the GNU General Public License
>> - * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> - *
>> - * Author: Will Deacon <will.deacon@arm.com>
>> - */
>> -
>> -#include <linux/linkage.h>
>> -#include <asm/asm-offsets.h>
>> -#include <asm/unistd.h>
>> -
>> -#define NSEC_PER_SEC_LO16	0xca00
>> -#define NSEC_PER_SEC_HI16	0x3b9a
>> -
>> -vdso_data	.req	x6
>> -seqcnt		.req	w7
>> -w_tmp		.req	w8
>> -x_tmp		.req	x8
>> -
>> -/*
>> - * Conventions for macro arguments:
>> - * - An argument is write-only if its name starts with "res".
>> - * - All other arguments are read-only, unless otherwise specified.
>> - */
>> -
>> -	.macro	seqcnt_acquire
>> -9999:	ldr	seqcnt, [vdso_data, #VDSO_TB_SEQ_COUNT]
>> -	tbnz	seqcnt, #0, 9999b
>> -	dmb	ishld
>> -	.endm
>> -
>> -	.macro	seqcnt_check fail
>> -	dmb	ishld
>> -	ldr	w_tmp, [vdso_data, #VDSO_TB_SEQ_COUNT]
>> -	cmp	w_tmp, seqcnt
>> -	b.ne	\fail
>> -	.endm
>> -
>> -	.macro	syscall_check fail
>> -	ldr	w_tmp, [vdso_data, #VDSO_USE_SYSCALL]
>> -	cbnz	w_tmp, \fail
>> -	.endm
>> -
>> -	.macro get_nsec_per_sec res
>> -	mov	\res, #NSEC_PER_SEC_LO16
>> -	movk	\res, #NSEC_PER_SEC_HI16, lsl #16
>> -	.endm
>> -
>> -	/*
>> -	 * Returns the clock delta, in nanoseconds left-shifted by the clock
>> -	 * shift.
>> -	 */
>> -	.macro	get_clock_shifted_nsec res, cycle_last, mult
>> -	/* Read the virtual counter. */
>> -	isb
>> -	mrs	x_tmp, cntvct_el0
>> -	/* Calculate cycle delta and convert to ns. */
>> -	sub	\res, x_tmp, \cycle_last
>> -	/* We can only guarantee 56 bits of precision. */
>> -	movn	x_tmp, #0xff00, lsl #48
>> -	and	\res, x_tmp, \res
>> -	mul	\res, \res, \mult
>> -	/*
>> -	 * Fake address dependency from the value computed from the counter
>> -	 * register to subsequent data page accesses so that the sequence
>> -	 * locking also orders the read of the counter.
>> -	 */
>> -	and	x_tmp, \res, xzr
>> -	add	vdso_data, vdso_data, x_tmp
>> -	.endm
>> -
>> -	/*
>> -	 * Returns in res_{sec,nsec} the REALTIME timespec, based on the
>> -	 * "wall time" (xtime) and the clock_mono delta.
>> -	 */
>> -	.macro	get_ts_realtime res_sec, res_nsec, \
>> -			clock_nsec, xtime_sec, xtime_nsec, nsec_to_sec
>> -	add	\res_nsec, \clock_nsec, \xtime_nsec
>> -	udiv	x_tmp, \res_nsec, \nsec_to_sec
>> -	add	\res_sec, \xtime_sec, x_tmp
>> -	msub	\res_nsec, x_tmp, \nsec_to_sec, \res_nsec
>> -	.endm
>> -
>> -	/*
>> -	 * Returns in res_{sec,nsec} the timespec based on the clock_raw delta,
>> -	 * used for CLOCK_MONOTONIC_RAW.
>> -	 */
>> -	.macro	get_ts_clock_raw res_sec, res_nsec, clock_nsec, nsec_to_sec
>> -	udiv	\res_sec, \clock_nsec, \nsec_to_sec
>> -	msub	\res_nsec, \res_sec, \nsec_to_sec, \clock_nsec
>> -	.endm
>> -
>> -	/* sec and nsec are modified in place. */
>> -	.macro add_ts sec, nsec, ts_sec, ts_nsec, nsec_to_sec
>> -	/* Add timespec. */
>> -	add	\sec, \sec, \ts_sec
>> -	add	\nsec, \nsec, \ts_nsec
>> -
>> -	/* Normalise the new timespec. */
>> -	cmp	\nsec, \nsec_to_sec
>> -	b.lt	9999f
>> -	sub	\nsec, \nsec, \nsec_to_sec
>> -	add	\sec, \sec, #1
>> -9999:
>> -	cmp	\nsec, #0
>> -	b.ge	9998f
>> -	add	\nsec, \nsec, \nsec_to_sec
>> -	sub	\sec, \sec, #1
>> -9998:
>> -	.endm
>> -
>> -	.macro clock_gettime_return, shift=0
>> -	.if \shift == 1
>> -	lsr	x11, x11, x12
>> -	.endif
>> -	stp	x10, x11, [x1, #TSPEC_TV_SEC]
>> -	mov	x0, xzr
>> -	ret
>> -	.endm
>> -
>> -	.macro jump_slot jumptable, index, label
>> -	.if (. - \jumptable) != 4 * (\index)
>> -	.error "Jump slot index mismatch"
>> -	.endif
>> -	b	\label
>> -	.endm
>> -
>> -	.text
>> -
>> -/* int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz); */
>> -ENTRY(__kernel_gettimeofday)
>> -	.cfi_startproc
>> -	adr	vdso_data, _vdso_data
>> -	/* If tv is NULL, skip to the timezone code. */
>> -	cbz	x0, 2f
>> -
>> -	/* Compute the time of day. */
>> -1:	seqcnt_acquire
>> -	syscall_check fail=4f
>> -	ldr	x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
>> -	/* w11 = cs_mono_mult, w12 = cs_shift */
>> -	ldp	w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
>> -	ldp	x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
>> -
>> -	get_nsec_per_sec res=x9
>> -	lsl	x9, x9, x12
>> -
>> -	get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
>> -	seqcnt_check fail=1b
>> -	get_ts_realtime res_sec=x10, res_nsec=x11, \
>> -		clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9
>> -
>> -	/* Convert ns to us. */
>> -	mov	x13, #1000
>> -	lsl	x13, x13, x12
>> -	udiv	x11, x11, x13
>> -	stp	x10, x11, [x0, #TVAL_TV_SEC]
>> -2:
>> -	/* If tz is NULL, return 0. */
>> -	cbz	x1, 3f
>> -	ldp	w4, w5, [vdso_data, #VDSO_TZ_MINWEST]
>> -	stp	w4, w5, [x1, #TZ_MINWEST]
>> -3:
>> -	mov	x0, xzr
>> -	ret
>> -4:
>> -	/* Syscall fallback. */
>> -	mov	x8, #__NR_gettimeofday
>> -	svc	#0
>> -	ret
>> -	.cfi_endproc
>> -ENDPROC(__kernel_gettimeofday)
>> -
>> -#define JUMPSLOT_MAX CLOCK_MONOTONIC_COARSE
>> -
>> -/* int __kernel_clock_gettime(clockid_t clock_id, struct timespec *tp); */
>> -ENTRY(__kernel_clock_gettime)
>> -	.cfi_startproc
>> -	cmp	w0, #JUMPSLOT_MAX
>> -	b.hi	syscall
>> -	adr	vdso_data, _vdso_data
>> -	adr	x_tmp, jumptable
>> -	add	x_tmp, x_tmp, w0, uxtw #2
>> -	br	x_tmp
>> -
>> -	ALIGN
>> -jumptable:
>> -	jump_slot jumptable, CLOCK_REALTIME, realtime
>> -	jump_slot jumptable, CLOCK_MONOTONIC, monotonic
>> -	b	syscall
>> -	b	syscall
>> -	jump_slot jumptable, CLOCK_MONOTONIC_RAW, monotonic_raw
>> -	jump_slot jumptable, CLOCK_REALTIME_COARSE, realtime_coarse
>> -	jump_slot jumptable, CLOCK_MONOTONIC_COARSE, monotonic_coarse
>> -
>> -	.if (. - jumptable) != 4 * (JUMPSLOT_MAX + 1)
>> -	.error	"Wrong jumptable size"
>> -	.endif
>> -
>> -	ALIGN
>> -realtime:
>> -	seqcnt_acquire
>> -	syscall_check fail=syscall
>> -	ldr	x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
>> -	/* w11 = cs_mono_mult, w12 = cs_shift */
>> -	ldp	w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
>> -	ldp	x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
>> -
>> -	/* All computations are done with left-shifted nsecs. */
>> -	get_nsec_per_sec res=x9
>> -	lsl	x9, x9, x12
>> -
>> -	get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
>> -	seqcnt_check fail=realtime
>> -	get_ts_realtime res_sec=x10, res_nsec=x11, \
>> -		clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9
>> -	clock_gettime_return, shift=1
>> -
>> -	ALIGN
>> -monotonic:
>> -	seqcnt_acquire
>> -	syscall_check fail=syscall
>> -	ldr	x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
>> -	/* w11 = cs_mono_mult, w12 = cs_shift */
>> -	ldp	w11, w12, [vdso_data, #VDSO_CS_MONO_MULT]
>> -	ldp	x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
>> -	ldp	x3, x4, [vdso_data, #VDSO_WTM_CLK_SEC]
>> -
>> -	/* All computations are done with left-shifted nsecs. */
>> -	lsl	x4, x4, x12
>> -	get_nsec_per_sec res=x9
>> -	lsl	x9, x9, x12
>> -
>> -	get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
>> -	seqcnt_check fail=monotonic
>> -	get_ts_realtime res_sec=x10, res_nsec=x11, \
>> -		clock_nsec=x15, xtime_sec=x13, xtime_nsec=x14, nsec_to_sec=x9
>> -
>> -	add_ts sec=x10, nsec=x11, ts_sec=x3, ts_nsec=x4, nsec_to_sec=x9
>> -	clock_gettime_return, shift=1
>> -
>> -	ALIGN
>> -monotonic_raw:
>> -	seqcnt_acquire
>> -	syscall_check fail=syscall
>> -	ldr	x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
>> -	/* w11 = cs_raw_mult, w12 = cs_shift */
>> -	ldp	w12, w11, [vdso_data, #VDSO_CS_SHIFT]
>> -	ldp	x13, x14, [vdso_data, #VDSO_RAW_TIME_SEC]
>> -
>> -	/* All computations are done with left-shifted nsecs. */
>> -	get_nsec_per_sec res=x9
>> -	lsl	x9, x9, x12
>> -
>> -	get_clock_shifted_nsec res=x15, cycle_last=x10, mult=x11
>> -	seqcnt_check fail=monotonic_raw
>> -	get_ts_clock_raw res_sec=x10, res_nsec=x11, \
>> -		clock_nsec=x15, nsec_to_sec=x9
>> -
>> -	add_ts sec=x10, nsec=x11, ts_sec=x13, ts_nsec=x14, nsec_to_sec=x9
>> -	clock_gettime_return, shift=1
>> -
>> -	ALIGN
>> -realtime_coarse:
>> -	seqcnt_acquire
>> -	ldp	x10, x11, [vdso_data, #VDSO_XTIME_CRS_SEC]
>> -	seqcnt_check fail=realtime_coarse
>> -	clock_gettime_return
>> -
>> -	ALIGN
>> -monotonic_coarse:
>> -	seqcnt_acquire
>> -	ldp	x10, x11, [vdso_data, #VDSO_XTIME_CRS_SEC]
>> -	ldp	x13, x14, [vdso_data, #VDSO_WTM_CLK_SEC]
>> -	seqcnt_check fail=monotonic_coarse
>> -
>> -	/* Computations are done in (non-shifted) nsecs. */
>> -	get_nsec_per_sec res=x9
>> -	add_ts sec=x10, nsec=x11, ts_sec=x13, ts_nsec=x14, nsec_to_sec=x9
>> -	clock_gettime_return
>> -
>> -	ALIGN
>> -syscall: /* Syscall fallback. */
>> -	mov	x8, #__NR_clock_gettime
>> -	svc	#0
>> -	ret
>> -	.cfi_endproc
>> -ENDPROC(__kernel_clock_gettime)
>> -
>> -/* int __kernel_clock_getres(clockid_t clock_id, struct timespec *res); */
>> -ENTRY(__kernel_clock_getres)
>> -	.cfi_startproc
>> -	cmp	w0, #CLOCK_REALTIME
>> -	ccmp	w0, #CLOCK_MONOTONIC, #0x4, ne
>> -	ccmp	w0, #CLOCK_MONOTONIC_RAW, #0x4, ne
>> -	b.ne	1f
>> -
>> -	adr	vdso_data, _vdso_data
>> -	ldr	w2, [vdso_data, #CLOCK_REALTIME_RES]
>> -	b	2f
>> -1:
>> -	cmp	w0, #CLOCK_REALTIME_COARSE
>> -	ccmp	w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne
>> -	b.ne	4f
>> -	ldr	x2, 5f
>> -2:
>> -	cbz	x1, 3f
>> -	stp	xzr, x2, [x1]
>> -
>> -3:	/* res == NULL. */
>> -	mov	w0, wzr
>> -	ret
>> -
>> -4:	/* Syscall fallback. */
>> -	mov	x8, #__NR_clock_getres
>> -	svc	#0
>> -	ret
>> -5:
>> -	.quad	CLOCK_COARSE_RES
>> -	.cfi_endproc
>> -ENDPROC(__kernel_clock_getres)
>> diff --git a/arch/arm64/kernel/vdso/vgettimeofday.c b/arch/arm64/kernel/vdso/vgettimeofday.c
>> new file mode 100644
>> index 000000000000..3c58f19dbdf4
>> --- /dev/null
>> +++ b/arch/arm64/kernel/vdso/vgettimeofday.c
>> @@ -0,0 +1,28 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * ARM64 userspace implementations of gettimeofday() and similar.
>> + *
>> + * Copyright (C) 2018 ARM Limited
>> + *
>> + */
>> +#include <linux/time.h>
>> +#include <linux/types.h>
>> +
>> +int __kernel_clock_gettime(clockid_t clock,
>> +			   struct __kernel_timespec *ts)
>> +{
>> +	return __cvdso_clock_gettime(clock, ts);
>> +}
>> +
>> +int __kernel_gettimeofday(struct __kernel_old_timeval *tv,
>> +			  struct timezone *tz)
>> +{
>> +	return __cvdso_gettimeofday(tv, tz);
>> +}
>> +
>> +int __kernel_clock_getres(clockid_t clock_id,
>> +			  struct __kernel_timespec *res)
>> +{
>> +	return __cvdso_clock_getres(clock_id, res);
>> +}
>> +
> 
> Best regards
> 

-- 
Regards,
Vincenzo