Re: [PATCH] time: Make NTP optionnal

From: peter enderborg
Date: Mon Nov 20 2017 - 10:22:15 EST

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On 11/20/2017 04:00 PM, Romain Perier wrote:
> Hi,
>
> 2017-11-20 15:10 GMT+01:00 peter enderborg <peter.enderborg@xxxxxxxx>:
>> I think it should return a error code at least.
> In which case ? The idea was to don't change the behaviour of these
> functions (from the "API" point of view) and to avoid regressions in
> the kernel components that depend on these NTP feature.
> (so be transparent the most as possible)
>
> Thanks,
> Romain
>

do_adjtimex should return -ENOSYS in my opinion, however it is not in the manual
that it can return ENOSYS.

>> On 11/02/2017 07:29 PM, Romain Perier wrote:
>>> On embedded systems with limited space, synchronizing system clock via
>>> NTP might be not needed.
>>>
>>> This commit introduces a new Kconfig entry. When disabled, it compiles
>>> out the adjtimex and clock_adjtimes system calls. The corresponding NTP
>>> accessors are also disabled from timekeeping.c and their declaration are
>>> replaced by no_op static inline functions in time.h
>>>
>>> The bloat-o-meter output is the following:
>>>
>>> add/remove: 1/35 grow/shrink: 2/9 up/down: 170/-3760 (-3590)
>>> function old new delta
>>> tk_set_wall_to_mono.constprop - 164 +164
>>> tk_xtime_add.constprop 200 204 +4
>>> timespec_trunc 60 62 +2
>>> ntp_notify_cmos_timer 2 - -2
>>> k_itimer_rcu_free 18 16 -2
>>> timekeeping_forward_now.constprop 256 252 -4
>>> time_status 4 - -4
>>> time_state 4 - -4
>>> time_maxerror 4 - -4
>>> time_esterror 4 - -4
>>> time_constant 4 - -4
>>> time_adjust 4 - -4
>>> tick_usec 4 - -4
>>> tick_nsec 4 - -4
>>> ntp_init 4 - -4
>>> posix_clock_realtime_adj 6 - -6
>>> time_reftime 8 - -8
>>> time_offset 8 - -8
>>> time_freq 8 - -8
>>> tick_length_base 8 - -8
>>> tick_length 8 - -8
>>> ntp_tick_adj 8 - -8
>>> ntp_next_leap_sec 8 - -8
>>> mask_to_bit_num 8 - -8
>>> mask_to_allowed_status 8 - -8
>>> ntp_tick_length 12 - -12
>>> __setup_ntp_tick_adj_setup 12 - -12
>>> __setup_str_ntp_tick_adj_setup 14 - -14
>>> timekeeping_resume 614 598 -16
>>> timekeeping_inject_offset 352 336 -16
>>> timekeeping_init 400 384 -16
>>> do_settimeofday64 342 326 -16
>>> ntp_tick_adj_setup 28 - -28
>>> timekeeping_update 236 206 -30
>>> branch_table 32 - -32
>>> sys_adjtimex 42 - -42
>>> sys_clock_adjtime 64 - -64
>>> ntp_clear 72 - -72
>>> ntp_get_next_leap 76 - -76
>>> ntp_validate_timex 78 - -78
>>> tk_set_wall_to_mono 166 - -166
>>> ntp_update_frequency 180 - -180
>>> update_wall_time 1846 1590 -256
>>> do_adjtimex 272 - -272
>>> second_overflow 476 - -476
>>> bcj_apply 1100 224 -876
>>> __do_adjtimex 888 - -888
>>>
>>> Signed-off-by: Romain Perier <romain.perier@xxxxxxxxx>
>>> ---
>>> include/linux/timex.h | 14 +++++++++++---
>>> init/Kconfig | 9 +++++++++
>>> kernel/compat.c | 2 ++
>>> kernel/sys_ni.c | 6 ++++++
>>> kernel/time/Makefile | 6 +++++-
>>> kernel/time/ntp_internal.h | 29 +++++++++++++++++++++++++++++
>>> kernel/time/posix-timers.c | 13 ++++++++-----
>>> kernel/time/time.c | 4 ++--
>>> kernel/time/timekeeping.c | 2 ++
>>> 9 files changed, 74 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/include/linux/timex.h b/include/linux/timex.h
>>> index 39c25dbebfe8..5906b654821a 100644
>>> --- a/include/linux/timex.h
>>> +++ b/include/linux/timex.h
>>> @@ -151,12 +151,20 @@ extern unsigned long tick_nsec; /* SHIFTED_HZ period (nsec) */
>>> #define NTP_INTERVAL_FREQ (HZ)
>>> #define NTP_INTERVAL_LENGTH (NSEC_PER_SEC/NTP_INTERVAL_FREQ)
>>>
>>> +#ifdef CONFIG_NTP
>>> extern int do_adjtimex(struct timex *);
>>> extern void hardpps(const struct timespec64 *, const struct timespec64 *);
>>> -
>>> -int read_current_timer(unsigned long *timer_val);
>>> void ntp_notify_cmos_timer(void);
>>> -
>>> +#else
>>> +static inline int do_adjtimex(struct timex *txc)
>>> +{
>>> + return TIME_OK;
>>> +}
>>> +static inline void hardpps(const struct timespec64 *phase_ts,
>>> + const struct timespec64 *raw_ts)
>>> +{}
>>> +#endif
>>> +int read_current_timer(unsigned long *timer_val);
>>> /* The clock frequency of the i8253/i8254 PIT */
>>> #define PIT_TICK_RATE 1193182ul
>>>
>>> diff --git a/init/Kconfig b/init/Kconfig
>>> index 3c1faaa2af4a..d4b0b33f7e91 100644
>>> --- a/init/Kconfig
>>> +++ b/init/Kconfig
>>> @@ -1332,6 +1332,15 @@ config EVENTFD
>>>
>>> If unsure, say Y.
>>>
>>> +config NTP
>>> + bool "Enable NTP support" if EXPERT
>>> + default y
>>> + help
>>> + This enables support for synchronizing system clock with NTP
>>> + and its corresponding syscalls adjtimex and clock_adjtimex.
>>> +
>>> + If unsure, say Y.
>>> +
>>> # syscall, maps, verifier
>>> config BPF_SYSCALL
>>> bool "Enable bpf() system call"
>>> diff --git a/kernel/compat.c b/kernel/compat.c
>>> index 772e038d04d9..12945ae5ae94 100644
>>> --- a/kernel/compat.c
>>> +++ b/kernel/compat.c
>>> @@ -30,6 +30,7 @@
>>>
>>> #include <linux/uaccess.h>
>>>
>>> +#ifdef CONFIG_NTP
>>> int compat_get_timex(struct timex *txc, const struct compat_timex __user *utp)
>>> {
>>> struct compat_timex tx32;
>>> @@ -91,6 +92,7 @@ int compat_put_timex(struct compat_timex __user *utp, const struct timex *txc)
>>> return -EFAULT;
>>> return 0;
>>> }
>>> +#endif
>>>
>>> static int __compat_get_timeval(struct timeval *tv, const struct compat_timeval __user *ctv)
>>> {
>>> diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
>>> index 8acef8576ce9..f854d24b813c 100644
>>> --- a/kernel/sys_ni.c
>>> +++ b/kernel/sys_ni.c
>>> @@ -258,3 +258,9 @@ cond_syscall(sys_membarrier);
>>> cond_syscall(sys_pkey_mprotect);
>>> cond_syscall(sys_pkey_alloc);
>>> cond_syscall(sys_pkey_free);
>>> +#ifndef CONFIG_NTP
>>> +cond_syscall(sys_adjtimex);
>>> +cond_syscall(sys_clock_adjtime);
>>> +cond_syscall(compat_sys_adjtimex);
>>> +cond_syscall(compat_sys_clock_adjtime);
>>> +#endif
>>> diff --git a/kernel/time/Makefile b/kernel/time/Makefile
>>> index 938dbf33ef49..44bd321e4560 100644
>>> --- a/kernel/time/Makefile
>>> +++ b/kernel/time/Makefile
>>> @@ -1,7 +1,11 @@
>>> obj-y += time.o timer.o hrtimer.o
>>> -obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o
>>> +obj-y += timekeeping.o clocksource.o jiffies.o timer_list.o
>>> obj-y += timeconv.o timecounter.o alarmtimer.o
>>>
>>> +ifeq ($(CONFIG_NTP),y)
>>> + obj-y += ntp.o
>>> +endif
>>> +
>>> ifeq ($(CONFIG_POSIX_TIMERS),y)
>>> obj-y += posix-timers.o posix-cpu-timers.o posix-clock.o itimer.o
>>> else
>>> diff --git a/kernel/time/ntp_internal.h b/kernel/time/ntp_internal.h
>>> index d8a7c11fa71a..9d1ebc042968 100644
>>> --- a/kernel/time/ntp_internal.h
>>> +++ b/kernel/time/ntp_internal.h
>>> @@ -1,6 +1,7 @@
>>> #ifndef _LINUX_NTP_INTERNAL_H
>>> #define _LINUX_NTP_INTERNAL_H
>>>
>>> +#ifdef CONFIG_NTP
>>> extern void ntp_init(void);
>>> extern void ntp_clear(void);
>>> /* Returns how long ticks are at present, in ns / 2^NTP_SCALE_SHIFT. */
>>> @@ -10,4 +11,32 @@ extern int second_overflow(time64_t secs);
>>> extern int ntp_validate_timex(struct timex *);
>>> extern int __do_adjtimex(struct timex *, struct timespec64 *, s32 *);
>>> extern void __hardpps(const struct timespec64 *, const struct timespec64 *);
>>> +#else
>>> +static inline void ntp_init(void)
>>> +{}
>>> +static inline void ntp_clear(void)
>>> +{}
>>> +static inline u64 ntp_tick_length(void)
>>> +{
>>> + return 0;
>>> +}
>>> +static inline ktime_t ntp_get_next_leap(void)
>>> +{
>>> + return KTIME_MAX;
>>> +}
>>> +static inline int second_overflow(time64_t secs)
>>> +{
>>> + return 0;
>>> +}
>>> +static inline int ntp_validate_timex(struct timex *txc)
>>> +{
>>> + return 0;
>>> +}
>>> +static inline int __do_adjtimex(struct timex *txc, struct timespec64 *ts,
>>> + s32 *time_tai)
>>> +{
>>> + return TIME_OK;
>>> +}
>>> +#endif
>>> +
>>> #endif /* _LINUX_NTP_INTERNAL_H */
>>> diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
>>> index 13d6881f908b..dd31eaddc196 100644
>>> --- a/kernel/time/posix-timers.c
>>> +++ b/kernel/time/posix-timers.c
>>> @@ -207,12 +207,13 @@ static int posix_clock_realtime_set(const clockid_t which_clock,
>>> return do_sys_settimeofday64(tp, NULL);
>>> }
>>>
>>> +#ifdef CONFIG_NTP
>>> static int posix_clock_realtime_adj(const clockid_t which_clock,
>>> struct timex *t)
>>> {
>>> return do_adjtimex(t);
>>> }
>>> -
>>> +#endif
>>> /*
>>> * Get monotonic time for posix timers
>>> */
>>> @@ -1065,7 +1066,7 @@ SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
>>>
>>> return error;
>>> }
>>> -
>>> +#ifdef CONFIG_NTP
>>> SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
>>> struct timex __user *, utx)
>>> {
>>> @@ -1088,7 +1089,7 @@ SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
>>>
>>> return err;
>>> }
>>> -
>>> +#endif
>>> SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
>>> struct timespec __user *, tp)
>>> {
>>> @@ -1141,7 +1142,7 @@ COMPAT_SYSCALL_DEFINE2(clock_gettime, clockid_t, which_clock,
>>>
>>> return err;
>>> }
>>> -
>>> +#ifdef CONFIG_NTP
>>> COMPAT_SYSCALL_DEFINE2(clock_adjtime, clockid_t, which_clock,
>>> struct compat_timex __user *, utp)
>>> {
>>> @@ -1165,7 +1166,7 @@ COMPAT_SYSCALL_DEFINE2(clock_adjtime, clockid_t, which_clock,
>>>
>>> return err;
>>> }
>>> -
>>> +#endif
>>> COMPAT_SYSCALL_DEFINE2(clock_getres, clockid_t, which_clock,
>>> struct compat_timespec __user *, tp)
>>> {
>>> @@ -1252,7 +1253,9 @@ static const struct k_clock clock_realtime = {
>>> .clock_getres = posix_get_hrtimer_res,
>>> .clock_get = posix_clock_realtime_get,
>>> .clock_set = posix_clock_realtime_set,
>>> +#ifdef CONFIG_NTP
>>> .clock_adj = posix_clock_realtime_adj,
>>> +#endif
>>> .nsleep = common_nsleep,
>>> .timer_create = common_timer_create,
>>> .timer_set = common_timer_set,
>>> diff --git a/kernel/time/time.c b/kernel/time/time.c
>>> index 44a8c1402133..413eca43a09c 100644
>>> --- a/kernel/time/time.c
>>> +++ b/kernel/time/time.c
>>> @@ -297,7 +297,7 @@ COMPAT_SYSCALL_DEFINE2(settimeofday, struct compat_timeval __user *, tv,
>>> return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
>>> }
>>> #endif
>>> -
>>> +#ifdef CONFIG_NTP
>>> SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
>>> {
>>> struct timex txc; /* Local copy of parameter */
>>> @@ -333,7 +333,7 @@ COMPAT_SYSCALL_DEFINE1(adjtimex, struct compat_timex __user *, utp)
>>> return ret;
>>> }
>>> #endif
>>> -
>>> +#endif
>>> /*
>>> * Convert jiffies to milliseconds and back.
>>> *
>>> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
>>> index 2cafb49aa65e..223fe15daa75 100644
>>> --- a/kernel/time/timekeeping.c
>>> +++ b/kernel/time/timekeeping.c
>>> @@ -2247,6 +2247,7 @@ ktime_t ktime_get_update_offsets_now(unsigned int *cwsseq, ktime_t *offs_real,
>>> return base;
>>> }
>>>
>>> +#ifdef CONFIG_NTP
>>> /**
>>> * do_adjtimex() - Accessor function to NTP __do_adjtimex function
>>> */
>>> @@ -2317,6 +2318,7 @@ void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
>>> }
>>> EXPORT_SYMBOL(hardpps);
>>> #endif /* CONFIG_NTP_PPS */
>>> +#endif /* CONFIG_NTP */
>>>
>>> /**
>>> * xtime_update() - advances the timekeeping infrastructure
>>

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