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posix-timers: Make them configurable 

Some embedded systems have no use for them.  This removes about
25KB 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, setitimer, getitimer, alarm.

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 which should cover the vast
majority of use cases with very little code.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: linux-kbuild@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: Michal Marek <mmarek@suse.com>
Cc: Edward Cree <ecree@solarflare.com>
Link: http://lkml.kernel.org/r/1478841010-28605-7-git-send-email-nicolas.pitre@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Nicolas Pitre 2016-11-11 00:10:10 -05:00 committed by Thomas Gleixner
parent 53d3eaa315
commit baa73d9e47
15 changed files with 200 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/alpha/kernel/osf_sys.c
View File

@ -1029,11 +1029,16 @@ SYSCALL_DEFINE2(osf_settimeofday, struct timeval32 __user *, tv,
return do_sys_settimeofday(tv ? &kts : NULL, tz ? &ktz : NULL);
}
asmlinkage long sys_ni_posix_timers(void);
SYSCALL_DEFINE2(osf_getitimer, int, which, struct itimerval32 __user *, it)
{
struct itimerval kit;
int error;
if (!IS_ENABLED(CONFIG_POSIX_TIMERS))
return sys_ni_posix_timers();
error = do_getitimer(which, &kit);
if (!error && put_it32(it, &kit))
error = -EFAULT;
@ -1047,6 +1052,9 @@ SYSCALL_DEFINE3(osf_setitimer, int, which, struct itimerval32 __user *, in,
struct itimerval kin, kout;
int error;
if (!IS_ENABLED(CONFIG_POSIX_TIMERS))
return sys_ni_posix_timers();
if (in) {
if (get_it32(&kin, in))
return -EFAULT;

1
drivers/char/Kconfig
View File

@ -542,6 +542,7 @@ config HANGCHECK_TIMER
config MMTIMER
tristate "MMTIMER Memory mapped RTC for SGI Altix"
depends on IA64_GENERIC || IA64_SGI_SN2
depends on POSIX_TIMERS
default y
help
The mmtimer device allows direct userspace access to the

2
drivers/ptp/Kconfig
View File

@ -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

2
fs/exec.c
View File

@ -1169,8 +1169,10 @@ no_thread_group:
/* we have changed execution domain */
tsk->exit_signal = SIGCHLD;
#ifdef CONFIG_POSIX_TIMERS
exit_itimers(sig);
flush_itimer_signals();
#endif
if (atomic_read(&oldsighand->count) != 1) {
struct sighand_struct *newsighand;

17
init/Kconfig
View File

@ -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.
Some embedded systems 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, getitimer,
setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
clock_getres and clock_nanosleep syscalls will be limited to
CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
If unsure say y.
config KALLSYMS
bool "Load all symbols for debugging/ksymoops" if EXPERT
default y

8
kernel/compat.c
View File

@ -307,12 +307,17 @@ static inline long put_compat_itimerval(struct compat_itimerval __user *o,
__put_user(i->it_value.tv_usec, &o->it_value.tv_usec)));
}
asmlinkage long sys_ni_posix_timers(void);
COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
struct compat_itimerval __user *, it)
{
struct itimerval kit;
int error;
if (!IS_ENABLED(CONFIG_POSIX_TIMERS))
return sys_ni_posix_timers();
error = do_getitimer(which, &kit);
if (!error && put_compat_itimerval(it, &kit))
error = -EFAULT;
@ -326,6 +331,9 @@ COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
struct itimerval kin, kout;
int error;
if (!IS_ENABLED(CONFIG_POSIX_TIMERS))
return sys_ni_posix_timers();
if (in) {
if (get_compat_itimerval(&kin, in))
return -EFAULT;

11
kernel/exit.c
View File

@ -92,11 +92,10 @@ static void __exit_signal(struct task_struct *tsk)
lockdep_tasklist_lock_is_held());
spin_lock(&sighand->siglock);
#ifdef CONFIG_POSIX_TIMERS
posix_cpu_timers_exit(tsk);
if (group_dead) {
posix_cpu_timers_exit_group(tsk);
tty = sig->tty;
sig->tty = NULL;
} else {
/*
* This can only happen if the caller is de_thread().
@ -105,7 +104,13 @@ static void __exit_signal(struct task_struct *tsk)
*/
if (unlikely(has_group_leader_pid(tsk)))
posix_cpu_timers_exit_group(tsk);
}
#endif
if (group_dead) {
tty = sig->tty;
sig->tty = NULL;
} else {
/*
* If there is any task waiting for the group exit
* then notify it:
@ -803,8 +808,10 @@ void __noreturn do_exit(long code)
acct_update_integrals(tsk);
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
#ifdef CONFIG_POSIX_TIMERS
hrtimer_cancel(&tsk->signal->real_timer);
exit_itimers(tsk->signal);
#endif
if (tsk->mm)
setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
}

2
kernel/fork.c
View File

@ -1342,8 +1342,10 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
seqlock_init(&sig->stats_lock);
prev_cputime_init(&sig->prev_cputime);
#ifdef CONFIG_POSIX_TIMERS
hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
sig->real_timer.function = it_real_fn;
#endif
task_lock(current->group_leader);
memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);

6
kernel/signal.c
View File

@ -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)
{
@ -567,6 +569,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
if (!signr) {
signr = __dequeue_signal(&tsk->signal->shared_pending,
mask, info);
#ifdef CONFIG_POSIX_TIMERS
/*
* itimer signal ?
*
@ -590,6 +593,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
hrtimer_restart(tmr);
}
}
#endif
}
recalc_sigpending();
@ -611,6 +615,7 @@ 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 +627,7 @@ 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;
}

3
kernel/sys.c
View File

@ -1416,7 +1416,8 @@ int do_prlimit(struct task_struct *tsk, unsigned int resource,
* applications, so we live with it
*/
if (!retval && new_rlim && resource == RLIMIT_CPU &&
new_rlim->rlim_cur != RLIM_INFINITY)
new_rlim->rlim_cur != RLIM_INFINITY &&
IS_ENABLED(CONFIG_POSIX_TIMERS))
update_rlimit_cpu(tsk, new_rlim->rlim_cur);
out:
read_unlock(&tasklist_lock);

10
kernel/time/Makefile
View File

@ -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
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 ($(CONFIG_POSIX_TIMERS),y)
obj-y += posix-timers.o posix-cpu-timers.o posix-clock.o itimer.o
else
obj-y += posix-stubs.o
endif
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o tick-common.o
ifeq ($(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST),y)

6
kernel/time/alarmtimer.c
View File

@ -846,8 +846,10 @@ static int __init alarmtimer_init(void)
alarmtimer_rtc_timer_init();
posix_timers_register_clock(CLOCK_REALTIME_ALARM, &alarm_clock);
posix_timers_register_clock(CLOCK_BOOTTIME_ALARM, &alarm_clock);
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;

123
kernel/time/posix-stubs.c Normal file
View File

@ -0,0 +1,123 @@
/*
* 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);
SYS_NI(getitimer);
SYS_NI(setitimer);
#ifdef __ARCH_WANT_SYS_ALARM
SYS_NI(alarm);
#endif
/*
* 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

3
kernel/time/timer.c
View File

@ -1601,7 +1601,8 @@ void update_process_times(int user_tick)
irq_work_tick();
#endif
scheduler_tick();
run_posix_cpu_timers(p);
if (IS_ENABLED(CONFIG_POSIX_TIMERS))
run_posix_cpu_timers(p);
}
/**

11
security/selinux/hooks.c
View File

@ -2525,7 +2525,8 @@ static void selinux_bprm_committing_creds(struct linux_binprm *bprm)
rlim->rlim_cur = min(rlim->rlim_max, initrlim->rlim_cur);
}
task_unlock(current);
update_rlimit_cpu(current, rlimit(RLIMIT_CPU));
if (IS_ENABLED(CONFIG_POSIX_TIMERS))
update_rlimit_cpu(current, rlimit(RLIMIT_CPU));
}
}
@ -2555,9 +2556,11 @@ static void selinux_bprm_committed_creds(struct linux_binprm *bprm)
*/
rc = avc_has_perm(osid, sid, SECCLASS_PROCESS, PROCESS__SIGINH, NULL);
if (rc) {
memset(&itimer, 0, sizeof itimer);
for (i = 0; i < 3; i++)
do_setitimer(i, &itimer, NULL);
if (IS_ENABLED(CONFIG_POSIX_TIMERS)) {
memset(&itimer, 0, sizeof itimer);
for (i = 0; i < 3; i++)
do_setitimer(i, &itimer, NULL);
}
spin_lock_irq(&current->sighand->siglock);
if (!fatal_signal_pending(current)) {
flush_sigqueue(&current->pending);