diff mbox

[4/4] posix-timers: make it configurable

Message ID 1476920573-14384-5-git-send-email-nicolas.pitre@linaro.org
State Superseded
Headers show

Commit Message

Nicolas Pitre Oct. 19, 2016, 11:42 p.m. UTC
Many embedded systems typically don't need them.  This removes about
22KB from the kernel binary size when configured out.

Corresponding syscalls are routed to a stub logging the attempt to
use those syscalls which should be enough of a clue if they were
disabled without proper consideration. They are: timer_create,
timer_gettime: timer_getoverrun, timer_settime, timer_delete,
clock_adjtime.

The clock_settime, clock_gettime, clock_getres and clock_nanosleep syscalls
are replaced by simple wrappers compatible with CLOCK_REALTIME,
CLOCK_MONOTONIC and CLOCK_BOOTTIME only.

Signed-off-by: Nicolas Pitre <nico@linaro.org>

---
 drivers/ptp/Kconfig          |   2 +-
 include/linux/posix-timers.h |  28 +++++++++-
 include/linux/sched.h        |  10 ++++
 init/Kconfig                 |  17 +++++++
 kernel/signal.c              |   4 ++
 kernel/time/Makefile         |  10 +++-
 kernel/time/posix-stubs.c    | 118 +++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 184 insertions(+), 5 deletions(-)
 create mode 100644 kernel/time/posix-stubs.c

-- 
2.7.4

Comments

Richard Cochran Oct. 20, 2016, 2:02 p.m. UTC | #1
On Wed, Oct 19, 2016 at 07:42:53PM -0400, Nicolas Pitre wrote:
> +config POSIX_TIMERS

> +	bool "Posix Clocks & timers" if EXPERT

> +	default y

> +	help

> +	  This includes native support for POSIX timers to the kernel.

> +	  Most embedded systems may have no use for them and therefore they


This sentence doesn't make sense.  How about:

	  Some embedded systems have no use for them ...

> +	  can be configured out to reduce the size of the kernel image.


Thanks,
Richard
Nicolas Pitre Oct. 20, 2016, 4:41 p.m. UTC | #2
On Thu, 20 Oct 2016, Richard Cochran wrote:

> On Wed, Oct 19, 2016 at 07:42:53PM -0400, Nicolas Pitre wrote:

> > +config POSIX_TIMERS

> > +	bool "Posix Clocks & timers" if EXPERT

> > +	default y

> > +	help

> > +	  This includes native support for POSIX timers to the kernel.

> > +	  Most embedded systems may have no use for them and therefore they

> 

> This sentence doesn't make sense.  How about:

> 

> 	  Some embedded systems have no use for them ...


As you wish.

Turns out that my own use of Fedora currently makes no use of them 
either.


Nicolas
diff mbox

Patch

diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
index 0f7492f8ea..bdce332911 100644
--- a/drivers/ptp/Kconfig
+++ b/drivers/ptp/Kconfig
@@ -6,7 +6,7 @@  menu "PTP clock support"
 
 config PTP_1588_CLOCK
 	tristate "PTP clock support"
-	depends on NET
+	depends on NET && POSIX_TIMERS
 	select PPS
 	select NET_PTP_CLASSIFY
 	help
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 62d44c1760..2288c5c557 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -118,6 +118,8 @@  struct k_clock {
 extern struct k_clock clock_posix_cpu;
 extern struct k_clock clock_posix_dynamic;
 
+#ifdef CONFIG_POSIX_TIMERS
+
 void posix_timers_register_clock(const clockid_t clock_id, struct k_clock *new_clock);
 
 /* function to call to trigger timer event */
@@ -131,8 +133,30 @@  void posix_cpu_timers_exit_group(struct task_struct *task);
 void set_process_cpu_timer(struct task_struct *task, unsigned int clock_idx,
 			   cputime_t *newval, cputime_t *oldval);
 
-long clock_nanosleep_restart(struct restart_block *restart_block);
-
 void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new);
 
+#else
+
+#include <linux/random.h>
+
+static inline void posix_timers_register_clock(const clockid_t clock_id,
+					       struct k_clock *new_clock) {}
+static inline int posix_timer_event(struct k_itimer *timr, int si_private)
+{ return 0; }
+static inline void run_posix_cpu_timers(struct task_struct *task) {}
+static inline void posix_cpu_timers_exit(struct task_struct *task)
+{
+	add_device_randomness((const void*) &task->se.sum_exec_runtime,
+			      sizeof(unsigned long long));
+}
+static inline void posix_cpu_timers_exit_group(struct task_struct *task) {}
+static inline void set_process_cpu_timer(struct task_struct *task,
+		unsigned int clock_idx, cputime_t *newval, cputime_t *oldval) {}
+static inline void update_rlimit_cpu(struct task_struct *task,
+				     unsigned long rlim_new) {}
+
+#endif
+
+long clock_nanosleep_restart(struct restart_block *restart_block);
+
 #endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 348f51b0ec..ad716d5559 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2946,8 +2946,13 @@  static inline void exit_thread(struct task_struct *tsk)
 extern void exit_files(struct task_struct *);
 extern void __cleanup_sighand(struct sighand_struct *);
 
+#ifdef CONFIG_POSIX_TIMERS
 extern void exit_itimers(struct signal_struct *);
 extern void flush_itimer_signals(void);
+#else
+static inline void exit_itimers(struct signal_struct *s) {}
+static inline void flush_itimer_signals(void) {}
+#endif
 
 extern void do_group_exit(int);
 
@@ -3450,7 +3455,12 @@  static __always_inline bool need_resched(void)
  * Thread group CPU time accounting.
  */
 void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times);
+#ifdef CONFIG_POSIX_TIMERS
 void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times);
+#else
+static inline void thread_group_cputimer(struct task_struct *tsk,
+					 struct task_cputime *times) {}
+#endif
 
 /*
  * Reevaluate whether the task has signals pending delivery.
diff --git a/init/Kconfig b/init/Kconfig
index 34407f15e6..351d422252 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1445,6 +1445,23 @@  config SYSCTL_SYSCALL
 
 	  If unsure say N here.
 
+config POSIX_TIMERS
+	bool "Posix Clocks & timers" if EXPERT
+	default y
+	help
+	  This includes native support for POSIX timers to the kernel.
+	  Most embedded systems may have no use for them and therefore they
+	  can be configured out to reduce the size of the kernel image.
+
+	  When this option is disabled, the following syscalls won't be
+	  available: timer_create, timer_gettime: timer_getoverrun,
+	  timer_settime, timer_delete, clock_adjtime. Furthermore, the
+	  clock_settime, clock_gettime, clock_getres and clock_nanosleep
+	  syscalls will be limited to CLOCK_REALTIME and CLOCK_MONOTONIC
+	  only.
+
+	  If unsure say y.
+
 config KALLSYMS
 	 bool "Load all symbols for debugging/ksymoops" if EXPERT
 	 default y
diff --git a/kernel/signal.c b/kernel/signal.c
index 75761acc77..0a38c9d646 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -427,6 +427,7 @@  void flush_signals(struct task_struct *t)
 	spin_unlock_irqrestore(&t->sighand->siglock, flags);
 }
 
+#ifdef CONFIG_POSIX_TIMERS
 static void __flush_itimer_signals(struct sigpending *pending)
 {
 	sigset_t signal, retain;
@@ -460,6 +461,7 @@  void flush_itimer_signals(void)
 	__flush_itimer_signals(&tsk->signal->shared_pending);
 	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 }
+#endif
 
 void ignore_signals(struct task_struct *t)
 {
@@ -611,6 +613,7 @@  int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
 		 */
 		current->jobctl |= JOBCTL_STOP_DEQUEUED;
 	}
+#ifdef CONFIG_POSIX_TIMERS
 	if ((info->si_code & __SI_MASK) == __SI_TIMER && info->si_sys_private) {
 		/*
 		 * Release the siglock to ensure proper locking order
@@ -622,6 +625,7 @@  int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
 		do_schedule_next_timer(info);
 		spin_lock(&tsk->sighand->siglock);
 	}
+#endif
 	return signr;
 }
 
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index 49eca0beed..fc26c308f5 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -1,6 +1,12 @@ 
-obj-y += time.o timer.o hrtimer.o itimer.o posix-timers.o posix-cpu-timers.o
+obj-y += time.o timer.o hrtimer.o itimer.o
 obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o
-obj-y += timeconv.o timecounter.o posix-clock.o alarmtimer.o
+obj-y += timeconv.o timecounter.o alarmtimer.o
+
+ifeq ($(CONFIG_POSIX_TIMERS),y)
+ obj-y += posix-timers.o posix-cpu-timers.o posix-clock.o
+else
+ obj-y += posix-stubs.o
+endif
 
 obj-$(CONFIG_GENERIC_CLOCKEVENTS)		+= clockevents.o tick-common.o
 ifeq ($(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST),y)
diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c
new file mode 100644
index 0000000000..fe857bd4a0
--- /dev/null
+++ b/kernel/time/posix-stubs.c
@@ -0,0 +1,118 @@ 
+/*
+ * Dummy stubs used when CONFIG_POSIX_TIMERS=n
+ *
+ * Created by:  Nicolas Pitre, July 2016
+ * Copyright:   (C) 2016 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/linkage.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/errno.h>
+#include <linux/syscalls.h>
+#include <linux/ktime.h>
+#include <linux/timekeeping.h>
+#include <linux/posix-timers.h>
+
+asmlinkage long sys_ni_posix_timers(void)
+{
+	pr_err_once("process %d (%s) attempted a POSIX timer syscall "
+		    "while CONFIG_POSIX_TIMERS is not set\n",
+		    current->pid, current->comm);
+	return -ENOSYS;
+}
+
+#define SYS_NI(name)  SYSCALL_ALIAS(sys_##name, sys_ni_posix_timers)
+
+SYS_NI(timer_create);
+SYS_NI(timer_gettime);
+SYS_NI(timer_getoverrun);
+SYS_NI(timer_settime);
+SYS_NI(timer_delete);
+SYS_NI(clock_adjtime);
+
+/*
+ * We preserve minimal support for CLOCK_REALTIME and CLOCK_MONOTONIC
+ * as it is easy to remain compatible with little code. CLOCK_BOOTTIME
+ * is also included for convenience as at least systemd uses it.
+ */
+
+SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
+		const struct timespec __user *, tp)
+{
+	struct timespec new_tp;
+
+	if (which_clock != CLOCK_REALTIME)
+		return -EINVAL;
+	if (copy_from_user(&new_tp, tp, sizeof (*tp)))
+		return -EFAULT;
+	return do_sys_settimeofday(&new_tp, NULL);
+}
+
+SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
+		struct timespec __user *,tp)
+{
+	struct timespec kernel_tp;
+
+	switch (which_clock) {
+	case CLOCK_REALTIME: ktime_get_real_ts(&kernel_tp); break;
+	case CLOCK_MONOTONIC: ktime_get_ts(&kernel_tp); break;
+	case CLOCK_BOOTTIME: get_monotonic_boottime(&kernel_tp); break;
+	default: return -EINVAL;
+	}
+	if (copy_to_user(tp, &kernel_tp, sizeof (kernel_tp)))
+		return -EFAULT;
+	return 0;
+}
+
+SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock, struct timespec __user *, tp)
+{
+	struct timespec rtn_tp = {
+		.tv_sec = 0,
+		.tv_nsec = hrtimer_resolution,
+	};
+
+	switch (which_clock) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_BOOTTIME:
+		if (copy_to_user(tp, &rtn_tp, sizeof(rtn_tp)))
+			return -EFAULT;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
+		const struct timespec __user *, rqtp,
+		struct timespec __user *, rmtp)
+{
+	struct timespec t;
+
+	switch (which_clock) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_BOOTTIME:
+		if (copy_from_user(&t, rqtp, sizeof (struct timespec)))
+			return -EFAULT;
+		if (!timespec_valid(&t))
+			return -EINVAL;
+		return hrtimer_nanosleep(&t, rmtp, flags & TIMER_ABSTIME ?
+					 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
+					 which_clock);
+	default:
+		return -EINVAL;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+long clock_nanosleep_restart(struct restart_block *restart_block)
+{
+	return hrtimer_nanosleep_restart(restart_block);
+}
+#endif