Messages in this thread | | | Date | Mon, 27 Nov 2023 16:11:58 -0800 | From | Richard Cochran <> | Subject | Re: [PATCH v2] posix-timers: add multi_clock_gettime system call |
| |
On Mon, Nov 27, 2023 at 05:39:01PM +0200, Sagi Maimon wrote: > Some user space applications need to read some clocks. > Each read requires moving from user space to kernel space. > This asymmetry causes the measured offset to have a significant error.
Adding time/clock gurus (jstultz, tglx) on CC for visibility...
Thanks, Richard
> > Introduce a new system call multi_clock_gettime, which can be used to measure > the offset between multiple clocks, from variety of types: PHC, virtual PHC > and various system clocks (CLOCK_REALTIME, CLOCK_MONOTONIC, etc). > The offset includes the total time that the driver needs to read the clock > timestamp. > > New system call allows the reading of a list of clocks - up to PTP_MAX_CLOCKS. > Supported clocks IDs: PHC, virtual PHC and various system clocks. > Up to PTP_MAX_SAMPLES times (per clock) in a single system call read. > The system call returns n_clocks timestamps for each measurement: > - clock 0 timestamp > - ... > - clock n timestamp > > Signed-off-by: Sagi Maimon <maimon.sagi@gmail.com> > --- > Addressed comments from: > - Richard Cochran : https://www.spinics.net/lists/netdev/msg951723.html > > Changes since version 1: > - Change multi PHC ioctl implamantation into systemcall. > > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > include/linux/posix-timers.h | 24 ++++++++++ > include/linux/syscalls.h | 3 +- > include/uapi/asm-generic/unistd.h | 12 ++++- > kernel/sys_ni.c | 1 + > kernel/time/posix-timers.c | 62 ++++++++++++++++++++++++++ > 7 files changed, 102 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl > index c8fac5205803..070efd266e7e 100644 > --- a/arch/x86/entry/syscalls/syscall_32.tbl > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > @@ -461,3 +461,4 @@ > 454 i386 futex_wake sys_futex_wake > 455 i386 futex_wait sys_futex_wait > 456 i386 futex_requeue sys_futex_requeue > +457 i386 multi_clock_gettime sys_multi_clock_gettime32 > \ No newline at end of file > diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl > index 8cb8bf68721c..f790330244bb 100644 > --- a/arch/x86/entry/syscalls/syscall_64.tbl > +++ b/arch/x86/entry/syscalls/syscall_64.tbl > @@ -378,6 +378,7 @@ > 454 common futex_wake sys_futex_wake > 455 common futex_wait sys_futex_wait > 456 common futex_requeue sys_futex_requeue > +457 common multi_clock_gettime sys_multi_clock_gettime > > # > # Due to a historical design error, certain syscalls are numbered differently > diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h > index d607f51404fc..426a45441ab5 100644 > --- a/include/linux/posix-timers.h > +++ b/include/linux/posix-timers.h > @@ -260,4 +260,28 @@ void set_process_cpu_timer(struct task_struct *task, unsigned int clock_idx, > int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new); > > void posixtimer_rearm(struct kernel_siginfo *info); > + > +#define MULTI_PTP_MAX_CLOCKS 12 /* Max number of clocks */ > +#define MULTI_PTP_MAX_SAMPLES 10 /* Max allowed offset measurement samples. */ > + > +struct __ptp_multi_clock_get { > + unsigned int n_clocks; /* Desired number of clocks. */ > + unsigned int n_samples; /* Desired number of measurements per clock. */ > + const clockid_t clkid_arr[MULTI_PTP_MAX_CLOCKS]; /* list of clock IDs */ > + /* > + * Array of list of n_clocks clocks time samples n_samples times. > + */ > + struct __kernel_timespec ts[MULTI_PTP_MAX_SAMPLES][MULTI_PTP_MAX_CLOCKS]; > +}; > + > +struct __ptp_multi_clock_get32 { > + unsigned int n_clocks; /* Desired number of clocks. */ > + unsigned int n_samples; /* Desired number of measurements per clock. */ > + const clockid_t clkid_arr[MULTI_PTP_MAX_CLOCKS]; /* list of clock IDs */ > + /* > + * Array of list of n_clocks clocks time samples n_samples times. > + */ > + struct old_timespec32 ts[MULTI_PTP_MAX_SAMPLES][MULTI_PTP_MAX_CLOCKS]; > +}; > + > #endif > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index fd9d12de7e92..afcf68e83d63 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -1161,7 +1161,8 @@ asmlinkage long sys_mmap_pgoff(unsigned long addr, unsigned long len, > unsigned long prot, unsigned long flags, > unsigned long fd, unsigned long pgoff); > asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg); > - > +asmlinkage long sys_multi_clock_gettime(struct __ptp_multi_clock_get __user * ptp_multi_clk_get); > +asmlinkage long sys_multi_clock_gettime32(struct __ptp_multi_clock_get32 __user * ptp_multi_clk_get); > > /* > * Not a real system call, but a placeholder for syscalls which are > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h > index 756b013fb832..3ebcaa052650 100644 > --- a/include/uapi/asm-generic/unistd.h > +++ b/include/uapi/asm-generic/unistd.h > @@ -829,8 +829,18 @@ __SYSCALL(__NR_futex_wait, sys_futex_wait) > #define __NR_futex_requeue 456 > __SYSCALL(__NR_futex_requeue, sys_futex_requeue) > > +#if defined(__ARCH_WANT_TIME32_SYSCALLS) || __BITS_PER_LONG != 32 > +#define __NR_multi_clock_gettime 457 > +__SC_3264(__NR_multi_clock_gettime, sys_multi_clock_gettime32, sys_multi_clock_gettime) > +#endif > + > +#if defined(__SYSCALL_COMPAT) || __BITS_PER_LONG == 32 > +#define __NR_multi_clock_gettime64 458 > +__SYSCALL(__NR_multi_clock_gettime64, sys_multi_clock_gettime) > +#endif > + > #undef __NR_syscalls > -#define __NR_syscalls 457 > +#define __NR_syscalls 459 > > /* > * 32 bit systems traditionally used different > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > index e1a6e3c675c0..8ed1c22f40ac 100644 > --- a/kernel/sys_ni.c > +++ b/kernel/sys_ni.c > @@ -335,6 +335,7 @@ COND_SYSCALL(ppoll_time32); > COND_SYSCALL_COMPAT(ppoll_time32); > COND_SYSCALL(utimensat_time32); > COND_SYSCALL(clock_adjtime32); > +COND_SYSCALL(multi_clock_gettime32); > > /* > * The syscalls below are not found in include/uapi/asm-generic/unistd.h > diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c > index b924f0f096fa..517558af2479 100644 > --- a/kernel/time/posix-timers.c > +++ b/kernel/time/posix-timers.c > @@ -1426,6 +1426,68 @@ SYSCALL_DEFINE4(clock_nanosleep_time32, clockid_t, which_clock, int, flags, > > #endif > > +SYSCALL_DEFINE1(multi_clock_gettime, struct __ptp_multi_clock_get __user *, ptp_multi_clk_get) > +{ > + const struct k_clock *kc; > + struct timespec64 kernel_tp; > + struct __ptp_multi_clock_get multi_clk_get; > + int error; > + unsigned int i, j; > + > + if (copy_from_user(&multi_clk_get, ptp_multi_clk_get, sizeof(multi_clk_get))) > + return -EFAULT; > + > + if (multi_clk_get.n_samples > MULTI_PTP_MAX_SAMPLES) > + return -EINVAL; > + if (multi_clk_get.n_clocks > MULTI_PTP_MAX_CLOCKS) > + return -EINVAL; > + > + for (j = 0; j < multi_clk_get.n_samples; j++) { > + for (i = 0; i < multi_clk_get.n_clocks; i++) { > + kc = clockid_to_kclock(multi_clk_get.clkid_arr[i]); > + if (!kc) > + return -EINVAL; > + error = kc->clock_get_timespec(multi_clk_get.clkid_arr[i], &kernel_tp); > + if (!error && put_timespec64(&kernel_tp, (struct __kernel_timespec __user *) > + &ptp_multi_clk_get->ts[j][i])) > + error = -EFAULT; > + } > + } > + > + return error; > +} > + > +SYSCALL_DEFINE1(multi_clock_gettime32, struct __ptp_multi_clock_get32 __user *, ptp_multi_clk_get) > +{ > + const struct k_clock *kc; > + struct timespec64 kernel_tp; > + struct __ptp_multi_clock_get multi_clk_get; > + int error; > + unsigned int i, j; > + > + if (copy_from_user(&multi_clk_get, ptp_multi_clk_get, sizeof(multi_clk_get))) > + return -EFAULT; > + > + if (multi_clk_get.n_samples > MULTI_PTP_MAX_SAMPLES) > + return -EINVAL; > + if (multi_clk_get.n_clocks > MULTI_PTP_MAX_CLOCKS) > + return -EINVAL; > + > + for (j = 0; j < multi_clk_get.n_samples; j++) { > + for (i = 0; i < multi_clk_get.n_clocks; i++) { > + kc = clockid_to_kclock(multi_clk_get.clkid_arr[i]); > + if (!kc) > + return -EINVAL; > + error = kc->clock_get_timespec(multi_clk_get.clkid_arr[i], &kernel_tp); > + if (!error && put_old_timespec32(&kernel_tp, (struct old_timespec32 __user *) > + &ptp_multi_clk_get->ts[j][i])) > + error = -EFAULT; > + } > + } > + > + return error; > +} > + > static const struct k_clock clock_realtime = { > .clock_getres = posix_get_hrtimer_res, > .clock_get_timespec = posix_get_realtime_timespec, > -- > 2.26.3 >
| |