Date:   Fri, 26 May 2017 12:03:11 +0300
From:   Christoph Hellwig <hch@....de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Dimitri Sivanich <sivanich@....com>,
        Mike Travis <mike.travis@....com>, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] kernel: mark all struct k_clock instances const

And initialize the array statically at compile time.   Originally
based on changes in the Grsecurity patch set, but redone for mainline
to be slightly cleaner, and take the SGI mmtimer removal into account,
which allows for a completely static initialization.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 include/linux/posix-timers.h   |   9 +-
 kernel/time/alarmtimer.c       |  27 +++---
 kernel/time/posix-clock.c      |   2 +-
 kernel/time/posix-cpu-timers.c |  34 +++-----
 kernel/time/posix-timers.c     | 191 +++++++++++++++++++----------------------
 5 files changed, 120 insertions(+), 143 deletions(-)

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 8c1e43ab14a9..b313ef2e7385 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -105,10 +105,11 @@ struct k_clock {
 			   struct itimerspec64 *cur_setting);
 };
 
-extern struct k_clock clock_posix_cpu;
-extern struct k_clock clock_posix_dynamic;
-
-void posix_timers_register_clock(const clockid_t clock_id, struct k_clock *new_clock);
+extern const struct k_clock clock_posix_cpu;
+extern const struct k_clock clock_posix_dynamic;
+extern const struct k_clock clock_process;
+extern const struct k_clock clock_thread;
+extern const struct k_clock alarm_clock;
 
 /* function to call to trigger timer event */
 int posix_timer_event(struct k_itimer *timr, int si_private);
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 5cb5b0008d97..2914ead22a8d 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -488,7 +488,7 @@ u64 alarm_forward_now(struct alarm *alarm, ktime_t interval)
 }
 EXPORT_SYMBOL_GPL(alarm_forward_now);
 
-
+#ifdef CONFIG_POSIX_TIMERS
 /**
  * clock2alarm - helper that converts from clockid to alarmtypes
  * @clockid: clockid.
@@ -860,6 +860,17 @@ static struct platform_driver alarmtimer_driver = {
 	}
 };
 
+const struct k_clock alarm_clock = {
+	.clock_getres	= alarm_clock_getres,
+	.clock_get	= alarm_clock_get,
+	.timer_create	= alarm_timer_create,
+	.timer_set	= alarm_timer_set,
+	.timer_del	= alarm_timer_del,
+	.timer_get	= alarm_timer_get,
+	.nsleep		= alarm_timer_nsleep,
+};
+#endif /* CONFIG_POSIX_TIMERS */
+
 /**
  * alarmtimer_init - Initialize alarm timer code
  *
@@ -871,23 +882,9 @@ static int __init alarmtimer_init(void)
 	struct platform_device *pdev;
 	int error = 0;
 	int i;
-	struct k_clock alarm_clock = {
-		.clock_getres	= alarm_clock_getres,
-		.clock_get	= alarm_clock_get,
-		.timer_create	= alarm_timer_create,
-		.timer_set	= alarm_timer_set,
-		.timer_del	= alarm_timer_del,
-		.timer_get	= alarm_timer_get,
-		.nsleep		= alarm_timer_nsleep,
-	};
 
 	alarmtimer_rtc_timer_init();
 
-	if (IS_ENABLED(CONFIG_POSIX_TIMERS)) {
-		posix_timers_register_clock(CLOCK_REALTIME_ALARM, &alarm_clock);
-		posix_timers_register_clock(CLOCK_BOOTTIME_ALARM, &alarm_clock);
-	}
-
 	/* Initialize alarm bases */
 	alarm_bases[ALARM_REALTIME].base_clockid = CLOCK_REALTIME;
 	alarm_bases[ALARM_REALTIME].gettime = &ktime_get_real;
diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c
index 31d588d37a17..7e453005e078 100644
--- a/kernel/time/posix-clock.c
+++ b/kernel/time/posix-clock.c
@@ -434,7 +434,7 @@ static int pc_timer_settime(struct k_itimer *kit, int flags,
 	return err;
 }
 
-struct k_clock clock_posix_dynamic = {
+const struct k_clock clock_posix_dynamic = {
 	.clock_getres	= pc_clock_getres,
 	.clock_set	= pc_clock_settime,
 	.clock_get	= pc_clock_gettime,
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 1370f067fb51..1a522b39f19d 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1413,7 +1413,7 @@ static int thread_cpu_timer_create(struct k_itimer *timer)
 	return posix_cpu_timer_create(timer);
 }
 
-struct k_clock clock_posix_cpu = {
+const struct k_clock clock_posix_cpu = {
 	.clock_getres	= posix_cpu_clock_getres,
 	.clock_set	= posix_cpu_clock_set,
 	.clock_get	= posix_cpu_clock_get,
@@ -1425,24 +1425,16 @@ struct k_clock clock_posix_cpu = {
 	.timer_get	= posix_cpu_timer_get,
 };
 
-static __init int init_posix_cpu_timers(void)
-{
-	struct k_clock process = {
-		.clock_getres	= process_cpu_clock_getres,
-		.clock_get	= process_cpu_clock_get,
-		.timer_create	= process_cpu_timer_create,
-		.nsleep		= process_cpu_nsleep,
-		.nsleep_restart	= process_cpu_nsleep_restart,
-	};
-	struct k_clock thread = {
-		.clock_getres	= thread_cpu_clock_getres,
-		.clock_get	= thread_cpu_clock_get,
-		.timer_create	= thread_cpu_timer_create,
-	};
-
-	posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
-	posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
+const struct k_clock clock_process = {
+	.clock_getres	= process_cpu_clock_getres,
+	.clock_get	= process_cpu_clock_get,
+	.timer_create	= process_cpu_timer_create,
+	.nsleep		= process_cpu_nsleep,
+	.nsleep_restart	= process_cpu_nsleep_restart,
+};
 
-	return 0;
-}
-__initcall(init_posix_cpu_timers);
+const struct k_clock clock_thread = {
+	.clock_getres	= thread_cpu_clock_getres,
+	.clock_get	= thread_cpu_clock_get,
+	.timer_create	= thread_cpu_timer_create,
+};
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 4d7b2ce09c27..0c0cccfa3586 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -125,8 +125,6 @@ static DEFINE_SPINLOCK(hash_lock);
  *	    which we beg off on and pass to do_sys_settimeofday().
  */
 
-static struct k_clock posix_clocks[MAX_CLOCKS];
-
 /*
  * These ones are defined below.
  */
@@ -280,74 +278,87 @@ static int posix_get_hrtimer_res(clockid_t which_clock, struct timespec64 *tp)
 	return 0;
 }
 
+
+static const struct k_clock clock_realtime = {
+	.clock_getres	= posix_get_hrtimer_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,
+	.timer_set	= common_timer_set,
+	.timer_get	= common_timer_get,
+	.timer_del	= common_timer_del,
+};
+
+static const struct k_clock clock_monotonic = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_ktime_get_ts,
+	.nsleep		= common_nsleep,
+	.nsleep_restart	= hrtimer_nanosleep_restart,
+	.timer_create	= common_timer_create,
+	.timer_set	= common_timer_set,
+	.timer_get	= common_timer_get,
+	.timer_del	= common_timer_del,
+};
+
+static const struct k_clock clock_monotonic_raw = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_get_monotonic_raw,
+};
+
+static const struct k_clock clock_realtime_coarse = {
+	.clock_getres	= posix_get_coarse_res,
+	.clock_get	= posix_get_realtime_coarse,
+};
+
+static const struct k_clock clock_monotonic_coarse = {
+	.clock_getres	= posix_get_coarse_res,
+	.clock_get	= posix_get_monotonic_coarse,
+};
+
+static const struct k_clock clock_tai = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_get_tai,
+	.nsleep		= common_nsleep,
+	.nsleep_restart	= hrtimer_nanosleep_restart,
+	.timer_create	= common_timer_create,
+	.timer_set	= common_timer_set,
+	.timer_get	= common_timer_get,
+	.timer_del	= common_timer_del,
+};
+
+static const struct k_clock clock_boottime = {
+	.clock_getres	= posix_get_hrtimer_res,
+	.clock_get	= posix_get_boottime,
+	.nsleep		= common_nsleep,
+	.nsleep_restart	= hrtimer_nanosleep_restart,
+	.timer_create	= common_timer_create,
+	.timer_set	= common_timer_set,
+	.timer_get	= common_timer_get,
+	.timer_del	= common_timer_del,
+};
+
+static const struct k_clock * const posix_clocks[] = {
+	[CLOCK_REALTIME]		= &clock_realtime,
+	[CLOCK_MONOTONIC]		= &clock_monotonic,
+	[CLOCK_PROCESS_CPUTIME_ID]	= &clock_process,
+	[CLOCK_THREAD_CPUTIME_ID]	= &clock_thread,
+	[CLOCK_MONOTONIC_RAW]		= &clock_monotonic_raw,
+	[CLOCK_REALTIME_COARSE]		= &clock_realtime_coarse,
+	[CLOCK_MONOTONIC_COARSE]	= &clock_monotonic_coarse,
+	[CLOCK_BOOTTIME]		= &clock_boottime,
+	[CLOCK_REALTIME_ALARM]		= &alarm_clock,
+	[CLOCK_BOOTTIME_ALARM]		= &alarm_clock,
+	[CLOCK_TAI]			= &clock_tai,
+};
+
 /*
  * Initialize everything, well, just everything in Posix clocks/timers ;)
  */
 static __init int init_posix_timers(void)
 {
-	struct k_clock clock_realtime = {
-		.clock_getres	= posix_get_hrtimer_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,
-		.timer_set	= common_timer_set,
-		.timer_get	= common_timer_get,
-		.timer_del	= common_timer_del,
-	};
-	struct k_clock clock_monotonic = {
-		.clock_getres	= posix_get_hrtimer_res,
-		.clock_get	= posix_ktime_get_ts,
-		.nsleep		= common_nsleep,
-		.nsleep_restart	= hrtimer_nanosleep_restart,
-		.timer_create	= common_timer_create,
-		.timer_set	= common_timer_set,
-		.timer_get	= common_timer_get,
-		.timer_del	= common_timer_del,
-	};
-	struct k_clock clock_monotonic_raw = {
-		.clock_getres	= posix_get_hrtimer_res,
-		.clock_get	= posix_get_monotonic_raw,
-	};
-	struct k_clock clock_realtime_coarse = {
-		.clock_getres	= posix_get_coarse_res,
-		.clock_get	= posix_get_realtime_coarse,
-	};
-	struct k_clock clock_monotonic_coarse = {
-		.clock_getres	= posix_get_coarse_res,
-		.clock_get	= posix_get_monotonic_coarse,
-	};
-	struct k_clock clock_tai = {
-		.clock_getres	= posix_get_hrtimer_res,
-		.clock_get	= posix_get_tai,
-		.nsleep		= common_nsleep,
-		.nsleep_restart	= hrtimer_nanosleep_restart,
-		.timer_create	= common_timer_create,
-		.timer_set	= common_timer_set,
-		.timer_get	= common_timer_get,
-		.timer_del	= common_timer_del,
-	};
-	struct k_clock clock_boottime = {
-		.clock_getres	= posix_get_hrtimer_res,
-		.clock_get	= posix_get_boottime,
-		.nsleep		= common_nsleep,
-		.nsleep_restart	= hrtimer_nanosleep_restart,
-		.timer_create	= common_timer_create,
-		.timer_set	= common_timer_set,
-		.timer_get	= common_timer_get,
-		.timer_del	= common_timer_del,
-	};
-
-	posix_timers_register_clock(CLOCK_REALTIME, &clock_realtime);
-	posix_timers_register_clock(CLOCK_MONOTONIC, &clock_monotonic);
-	posix_timers_register_clock(CLOCK_MONOTONIC_RAW, &clock_monotonic_raw);
-	posix_timers_register_clock(CLOCK_REALTIME_COARSE, &clock_realtime_coarse);
-	posix_timers_register_clock(CLOCK_MONOTONIC_COARSE, &clock_monotonic_coarse);
-	posix_timers_register_clock(CLOCK_BOOTTIME, &clock_boottime);
-	posix_timers_register_clock(CLOCK_TAI, &clock_tai);
-
 	posix_timers_cache = kmem_cache_create("posix_timers_cache",
 					sizeof (struct k_itimer), 0, SLAB_PANIC,
 					NULL);
@@ -521,30 +532,6 @@ static struct pid *good_sigevent(sigevent_t * event)
 	return task_pid(rtn);
 }
 
-void posix_timers_register_clock(const clockid_t clock_id,
-				 struct k_clock *new_clock)
-{
-	if ((unsigned) clock_id >= MAX_CLOCKS) {
-		printk(KERN_WARNING "POSIX clock register failed for clock_id %d\n",
-		       clock_id);
-		return;
-	}
-
-	if (!new_clock->clock_get) {
-		printk(KERN_WARNING "POSIX clock id %d lacks clock_get()\n",
-		       clock_id);
-		return;
-	}
-	if (!new_clock->clock_getres) {
-		printk(KERN_WARNING "POSIX clock id %d lacks clock_getres()\n",
-		       clock_id);
-		return;
-	}
-
-	posix_clocks[clock_id] = *new_clock;
-}
-EXPORT_SYMBOL_GPL(posix_timers_register_clock);
-
 static struct k_itimer * alloc_posix_timer(void)
 {
 	struct k_itimer *tmr;
@@ -581,15 +568,15 @@ static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
 	call_rcu(&tmr->it.rcu, k_itimer_rcu_free);
 }
 
-static struct k_clock *clockid_to_kclock(const clockid_t id)
+static const struct k_clock *clockid_to_kclock(const clockid_t id)
 {
 	if (id < 0)
 		return (id & CLOCKFD_MASK) == CLOCKFD ?
 			&clock_posix_dynamic : &clock_posix_cpu;
 
-	if (id >= MAX_CLOCKS || !posix_clocks[id].clock_getres)
+	if (id >= ARRAY_SIZE(posix_clocks) || !posix_clocks[id])
 		return NULL;
-	return &posix_clocks[id];
+	return posix_clocks[id];
 }
 
 static int common_timer_create(struct k_itimer *new_timer)
@@ -604,7 +591,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
 		struct sigevent __user *, timer_event_spec,
 		timer_t __user *, created_timer_id)
 {
-	struct k_clock *kc = clockid_to_kclock(which_clock);
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
 	struct k_itimer *new_timer;
 	int error, new_timer_id;
 	sigevent_t event;
@@ -781,7 +768,7 @@ SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
 	struct itimerspec64 cur_setting64;
 	struct itimerspec cur_setting;
 	struct k_itimer *timr;
-	struct k_clock *kc;
+	const struct k_clock *kc;
 	unsigned long flags;
 	int ret = 0;
 
@@ -890,7 +877,7 @@ SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
 	struct itimerspec new_spec, old_spec;
 	struct k_itimer *timr;
 	unsigned long flag;
-	struct k_clock *kc;
+	const struct k_clock *kc;
 	int error = 0;
 
 	if (!new_setting)
@@ -939,7 +926,7 @@ static int common_timer_del(struct k_itimer *timer)
 
 static inline int timer_delete_hook(struct k_itimer *timer)
 {
-	struct k_clock *kc = clockid_to_kclock(timer->it_clock);
+	const struct k_clock *kc = clockid_to_kclock(timer->it_clock);
 
 	if (WARN_ON_ONCE(!kc || !kc->timer_del))
 		return -EINVAL;
@@ -1018,7 +1005,7 @@ void exit_itimers(struct signal_struct *sig)
 SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
 		const struct timespec __user *, tp)
 {
-	struct k_clock *kc = clockid_to_kclock(which_clock);
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
 	struct timespec64 new_tp64;
 	struct timespec new_tp;
 
@@ -1035,7 +1022,7 @@ SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
 SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
 		struct timespec __user *,tp)
 {
-	struct k_clock *kc = clockid_to_kclock(which_clock);
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
 	struct timespec64 kernel_tp64;
 	struct timespec kernel_tp;
 	int error;
@@ -1055,7 +1042,7 @@ SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
 SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
 		struct timex __user *, utx)
 {
-	struct k_clock *kc = clockid_to_kclock(which_clock);
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
 	struct timex ktx;
 	int err;
 
@@ -1078,7 +1065,7 @@ SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
 SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
 		struct timespec __user *, tp)
 {
-	struct k_clock *kc = clockid_to_kclock(which_clock);
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
 	struct timespec64 rtn_tp64;
 	struct timespec rtn_tp;
 	int error;
@@ -1110,7 +1097,7 @@ SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
 		const struct timespec __user *, rqtp,
 		struct timespec __user *, rmtp)
 {
-	struct k_clock *kc = clockid_to_kclock(which_clock);
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
 	struct timespec64 t64;
 	struct timespec t;
 
@@ -1136,7 +1123,7 @@ SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
 long clock_nanosleep_restart(struct restart_block *restart_block)
 {
 	clockid_t which_clock = restart_block->nanosleep.clockid;
-	struct k_clock *kc = clockid_to_kclock(which_clock);
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
 
 	if (WARN_ON_ONCE(!kc || !kc->nsleep_restart))
 		return -EINVAL;
-- 
2.11.0

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