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Subject[patch 25/28] posix clocks: Introduce a syscall for clock tuning.
From: Richard Cochran <richardcochran@gmail.com>

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>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Miller <davem@davemloft.net>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Krzysztof Halasa <khc@pm.waw.pl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rodolfo Giometti <giometti@linux.it>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Russell King <linux@arm.linux.org.uk>
LKML-Reference: <2d5e2f3e6f388aa1848d40406646aab2e26a906f.1296124770.git.richard.cochran@omicron.at>
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(+)
Index: linux-2.6-tip/include/linux/posix-timers.h
===================================================================
--- linux-2.6-tip.orig/include/linux/posix-timers.h
+++ linux-2.6-tip/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 *);
Index: linux-2.6-tip/include/linux/syscalls.h
===================================================================
--- linux-2.6-tip.orig/include/linux/syscalls.h
+++ linux-2.6-tip/include/linux/syscalls.h
@@ -311,6 +311,8 @@ asmlinkage long sys_clock_settime(clocki
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,
Index: linux-2.6-tip/kernel/compat.c
===================================================================
--- linux-2.6-tip.orig/kernel/compat.c
+++ linux-2.6-tip/kernel/compat.c
@@ -675,6 +675,29 @@ long compat_sys_clock_gettime(clockid_t
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)
{
Index: linux-2.6-tip/kernel/posix-timers.c
===================================================================
--- linux-2.6-tip.orig/kernel/posix-timers.c
+++ linux-2.6-tip/kernel/posix-timers.c
@@ -170,6 +170,12 @@ static inline int posix_clock_realtime_s
return do_sys_settimeofday(tp, NULL);
}

+static inline 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,
@@ -930,6 +937,29 @@ SYSCALL_DEFINE2(clock_gettime, const clo
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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