Re: [PATCH] time: Make NTP optionnal

From: Romain Perier
Date: Mon Nov 20 2017 - 10:00:31 EST

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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

>
> 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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In reply to: peter enderborg: "Re: [PATCH] time: Make NTP optionnal"
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