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>

4 files changed, 57 insertions, 0 deletions

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 8206255a547c..79a1cea7f6ed 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 18cd0684fc4e..bfacab921239 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 449e853cf41d..38b1d2c1cbe8 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 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)
 {