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    Subject[tip:timers/core] posix-timers: Introduce a syscall for clock tuning.
    Commit-ID:  f1f1d5ebd10ffa4242bce7a90a56a222d6b7bc77
    Gitweb: http://git.kernel.org/tip/f1f1d5ebd10ffa4242bce7a90a56a222d6b7bc77
    Author: Richard Cochran <richardcochran@gmail.com>
    AuthorDate: Tue, 1 Feb 2011 13:52:26 +0000
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Wed, 2 Feb 2011 15:28:19 +0100

    posix-timers: Introduce a syscall for clock tuning.

    A new syscall is introduced that allows tuning of a POSIX clock. The
    new call, clock_adjtime, takes two parameters, the clock ID and a
    pointer to a struct timex. Any ADJTIMEX(2) operation may be requested
    via this system call, but various POSIX clocks may or may not support
    tuning.

    [ tglx: Adapted to the posix-timer cleanup series. Avoid copy_to_user
    in the error case ]

    Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
    Acked-by: John Stultz <johnstul@us.ibm.com>
    LKML-Reference: <20110201134419.869804645@linutronix.de>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    include/linux/posix-timers.h | 2 ++
    include/linux/syscalls.h | 2 ++
    kernel/compat.c | 23 +++++++++++++++++++++++
    kernel/posix-timers.c | 30 ++++++++++++++++++++++++++++++
    4 files changed, 57 insertions(+), 0 deletions(-)

    diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
    index 8206255..79a1cea 100644
    --- a/include/linux/posix-timers.h
    +++ b/include/linux/posix-timers.h
    @@ -4,6 +4,7 @@
    #include <linux/spinlock.h>
    #include <linux/list.h>
    #include <linux/sched.h>
    +#include <linux/timex.h>

    union cpu_time_count {
    cputime_t cpu;
    @@ -71,6 +72,7 @@ struct k_clock {
    int (*clock_set) (const clockid_t which_clock,
    const struct timespec *tp);
    int (*clock_get) (const clockid_t which_clock, struct timespec * tp);
    + int (*clock_adj) (const clockid_t which_clock, struct timex *tx);
    int (*timer_create) (struct k_itimer *timer);
    int (*nsleep) (const clockid_t which_clock, int flags,
    struct timespec *, struct timespec __user *);
    diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
    index 18cd068..bfacab9 100644
    --- a/include/linux/syscalls.h
    +++ b/include/linux/syscalls.h
    @@ -311,6 +311,8 @@ asmlinkage long sys_clock_settime(clockid_t which_clock,
    const struct timespec __user *tp);
    asmlinkage long sys_clock_gettime(clockid_t which_clock,
    struct timespec __user *tp);
    +asmlinkage long sys_clock_adjtime(clockid_t which_clock,
    + struct timex __user *tx);
    asmlinkage long sys_clock_getres(clockid_t which_clock,
    struct timespec __user *tp);
    asmlinkage long sys_clock_nanosleep(clockid_t which_clock, int flags,
    diff --git a/kernel/compat.c b/kernel/compat.c
    index 449e853..38b1d2c 100644
    --- a/kernel/compat.c
    +++ b/kernel/compat.c
    @@ -675,6 +675,29 @@ long compat_sys_clock_gettime(clockid_t which_clock,
    return err;
    }

    +long compat_sys_clock_adjtime(clockid_t which_clock,
    + struct compat_timex __user *utp)
    +{
    + struct timex txc;
    + mm_segment_t oldfs;
    + int err, ret;
    +
    + err = compat_get_timex(&txc, utp);
    + if (err)
    + return err;
    +
    + oldfs = get_fs();
    + set_fs(KERNEL_DS);
    + ret = sys_clock_adjtime(which_clock, (struct timex __user *) &txc);
    + set_fs(oldfs);
    +
    + err = compat_put_timex(utp, &txc);
    + if (err)
    + return err;
    +
    + return ret;
    +}
    +
    long compat_sys_clock_getres(clockid_t which_clock,
    struct compat_timespec __user *tp)
    {
    diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
    index a3fdfd4..5a5a4f1 100644
    --- a/kernel/posix-timers.c
    +++ b/kernel/posix-timers.c
    @@ -170,6 +170,12 @@ static int posix_clock_realtime_set(const clockid_t which_clock,
    return do_sys_settimeofday(tp, NULL);
    }

    +static int posix_clock_realtime_adj(const clockid_t which_clock,
    + struct timex *t)
    +{
    + return do_adjtimex(t);
    +}
    +
    /*
    * Get monotonic time for posix timers
    */
    @@ -216,6 +222,7 @@ static __init int init_posix_timers(void)
    .clock_getres = hrtimer_get_res,
    .clock_get = posix_clock_realtime_get,
    .clock_set = posix_clock_realtime_set,
    + .clock_adj = posix_clock_realtime_adj,
    .nsleep = common_nsleep,
    .nsleep_restart = hrtimer_nanosleep_restart,
    .timer_create = common_timer_create,
    @@ -948,6 +955,29 @@ SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
    return error;
    }

    +SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
    + struct timex __user *, utx)
    +{
    + struct k_clock *kc = clockid_to_kclock(which_clock);
    + struct timex ktx;
    + int err;
    +
    + if (!kc)
    + return -EINVAL;
    + if (!kc->clock_adj)
    + return -EOPNOTSUPP;
    +
    + if (copy_from_user(&ktx, utx, sizeof(ktx)))
    + return -EFAULT;
    +
    + err = kc->clock_adj(which_clock, &ktx);
    +
    + if (!err && copy_to_user(utx, &ktx, sizeof(ktx)))
    + return -EFAULT;
    +
    + return err;
    +}
    +
    SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
    struct timespec __user *, tp)
    {

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