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>

1 files changed, 30 insertions, 0 deletions

diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index a3fdfd4be0ec..5a5a4f1c0971 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)
 {