[PATCH 1/2] posix clocks: introduce a syscall for clock tuning.

Richard Cochran
2010-09-03T09:29:05Z

A new syscall is introduced that allows tuning of a POSIX clock. The
syscall is implemented for four architectures: arm, blackfin, powerpc,
and x86.

The new syscall, clock_adjtime, takes two parameters, the clock ID,
and a pointer to a struct timex. The semantics of the timex struct
have been expanded by one additional mode flag, which allows an
absolute offset correction. When specificied, the clock offset is
immediately corrected by skipping to the new time value.

In addition, the POSIX clock code has been augmented to offer a
dynamic clock creation method. Instead of registering a hard
coded clock ID, modules may call create_posix_clock(), which
returns a new clock ID.

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
---
arch/arm/include/asm/unistd.h | 1 +
arch/arm/kernel/calls.S | 1 +
arch/blackfin/include/asm/unistd.h | 3 +-
arch/blackfin/mach-common/entry.S | 1 +
arch/powerpc/include/asm/systbl.h | 1 +
arch/powerpc/include/asm/unistd.h | 3 +-
arch/x86/ia32/ia32entry.S | 1 +
arch/x86/include/asm/unistd_32.h | 3 +-
arch/x86/include/asm/unistd_64.h | 2 +
arch/x86/kernel/syscall_table_32.S | 1 +
include/linux/posix-timers.h | 10 +++-
include/linux/syscalls.h | 2 +
include/linux/time.h | 2 +
include/linux/timex.h | 3 +-
kernel/compat.c | 136 +++++++++++++++++++++++-------------
kernel/posix-cpu-timers.c | 4 +
kernel/posix-timers.c | 58 +++++++++++++--
17 files changed, 172 insertions(+), 60 deletions(-)

diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index dd2bf53..6bea0b7 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -392,6 +392,7 @@
#define __NR_rt_tgsigqueueinfo (__NR_SYSCALL_BASE+363)
#define __NR_perf_event_open (__NR_SYSCALL_BASE+364)
#define __NR_recvmmsg (__NR_SYSCALL_BASE+365)
+#define __NR_clock_adjtime (__NR_SYSCALL_BASE+366)

/*
* The following SWIs are ARM private.
diff --git a/arch/arm/kernel/calls.S b/arch/arm/kernel/calls.S
index 37ae301..8a22fdd 100644
--- a/arch/arm/kernel/calls.S
+++ b/arch/arm/kernel/calls.S
@@ -375,6 +375,7 @@
CALL(sys_rt_tgsigqueueinfo)
CALL(sys_perf_event_open)
/* 365 */ CALL(sys_recvmmsg)
+ CALL(sys_clock_adjtime)
#ifndef syscalls_counted
.equ syscalls_padding, ((NR_syscalls + 3) & ~3) - NR_syscalls
#define syscalls_counted
diff --git a/arch/blackfin/include/asm/unistd.h b/arch/blackfin/include/asm/unistd.h
index 22886cb..6671913 100644
--- a/arch/blackfin/include/asm/unistd.h
+++ b/arch/blackfin/include/asm/unistd.h
@@ -389,8 +389,9 @@
#define __NR_rt_tgsigqueueinfo 368
#define __NR_perf_event_open 369
#define __NR_recvmmsg 370
+#define __NR_clock_adjtime 371

-#define __NR_syscall 371
+#define __NR_syscall 372
#define NR_syscalls __NR_syscall

/* Old optional stuff no one actually uses */
diff --git a/arch/blackfin/mach-common/entry.S b/arch/blackfin/mach-common/entry.S
index a5847f5..252f2fa 100644
--- a/arch/blackfin/mach-common/entry.S
+++ b/arch/blackfin/mach-common/entry.S
@@ -1628,6 +1628,7 @@ ENTRY(_sys_call_table)
.long _sys_rt_tgsigqueueinfo
.long _sys_perf_event_open
.long _sys_recvmmsg /* 370 */
+ .long _sys_clock_adjtime

.rept NR_syscalls-(.-_sys_call_table)/4
.long _sys_ni_syscall
diff --git a/arch/powerpc/include/asm/systbl.h b/arch/powerpc/include/asm/systbl.h
index a5ee345..e7dce86 100644
--- a/arch/powerpc/include/asm/systbl.h
+++ b/arch/powerpc/include/asm/systbl.h
@@ -326,3 +326,4 @@ SYSCALL_SPU(perf_event_open)
COMPAT_SYS_SPU(preadv)
COMPAT_SYS_SPU(pwritev)
COMPAT_SYS(rt_tgsigqueueinfo)
+COMPAT_SYS_SPU(clock_adjtime)
diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
index f0a1026..7d4d9c8 100644
--- a/arch/powerpc/include/asm/unistd.h
+++ b/arch/powerpc/include/asm/unistd.h
@@ -345,10 +345,11 @@
#define __NR_preadv 320
#define __NR_pwritev 321
#define __NR_rt_tgsigqueueinfo 322
+#define __NR_clock_adjtime 323

#ifdef __KERNEL__

-#define __NR_syscalls 323
+#define __NR_syscalls 324

#define __NR__exit __NR_exit
#define NR_syscalls __NR_syscalls
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index b86feab..2771351 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -845,4 +845,5 @@ ia32_sys_call_table:
.quad sys_fanotify_init
.quad sys32_fanotify_mark
.quad sys_prlimit64 /* 340 */
+ .quad compat_sys_clock_adjtime
ia32_syscall_end:
diff --git a/arch/x86/include/asm/unistd_32.h b/arch/x86/include/asm/unistd_32.h
index b766a5e..b6f73f1 100644
--- a/arch/x86/include/asm/unistd_32.h
+++ b/arch/x86/include/asm/unistd_32.h
@@ -346,10 +346,11 @@
#define __NR_fanotify_init 338
#define __NR_fanotify_mark 339
#define __NR_prlimit64 340
+#define __NR_clock_adjtime 341

#ifdef __KERNEL__

-#define NR_syscalls 341
+#define NR_syscalls 342

#define __ARCH_WANT_IPC_PARSE_VERSION
#define __ARCH_WANT_OLD_READDIR
diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h
index 363e9b8..5ee3085 100644
--- a/arch/x86/include/asm/unistd_64.h
+++ b/arch/x86/include/asm/unistd_64.h
@@ -669,6 +669,8 @@ __SYSCALL(__NR_fanotify_init, sys_fanotify_init)
__SYSCALL(__NR_fanotify_mark, sys_fanotify_mark)
#define __NR_prlimit64 302
__SYSCALL(__NR_prlimit64, sys_prlimit64)
+#define __NR_clock_adjtime 303
+__SYSCALL(__NR_clock_adjtime, sys_clock_adjtime)

#ifndef __NO_STUBS
#define __ARCH_WANT_OLD_READDIR
diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
index b35786d..68c7b9a 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -340,3 +340,4 @@ ENTRY(sys_call_table)
.long sys_fanotify_init
.long sys_fanotify_mark
.long sys_prlimit64 /* 340 */
+ .long sys_clock_adjtime
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 3e23844..08aa4da 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;
@@ -67,10 +68,12 @@ struct k_itimer {
};

struct k_clock {
+ clockid_t id;
int res; /* in nanoseconds */
int (*clock_getres) (const clockid_t which_clock, struct timespec *tp);
int (*clock_set) (const clockid_t which_clock, 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 *);
@@ -84,7 +87,11 @@ struct k_clock {
struct itimerspec * cur_setting);
};

-void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock);
+/* Regsiter a posix clock with a "well known" clock id. */
+int register_posix_clock(const clockid_t id, struct k_clock *clock);
+
+/* Create a new posix clock with a dynamic clock id. */
+clockid_t create_posix_clock(struct k_clock *clock);

/* error handlers for timer_create, nanosleep and settime */
int do_posix_clock_nonanosleep(const clockid_t, int flags, struct timespec *,
@@ -97,6 +104,7 @@ int posix_timer_event(struct k_itimer *timr, int si_private);
int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *ts);
int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *ts);
int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *ts);
+int posix_cpu_clock_adj(const clockid_t which_clock, struct timex *tx);
int posix_cpu_timer_create(struct k_itimer *timer);
int posix_cpu_nsleep(const clockid_t which_clock, int flags,
struct timespec *rqtp, struct timespec __user *rmtp);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 6e5d197..0f4d57c 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -313,6 +313,8 @@ 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/include/linux/time.h b/include/linux/time.h
index 9f15ac7..914c48d 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -299,6 +299,8 @@ struct itimerval {
#define CLOCKS_MASK (CLOCK_REALTIME | CLOCK_MONOTONIC)
#define CLOCKS_MONO CLOCK_MONOTONIC

+#define CLOCK_INVALID -1
+
/*
* The various flags for setting POSIX.1b interval timers:
*/
diff --git a/include/linux/timex.h b/include/linux/timex.h
index 32d852f..82d4b24 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -73,7 +73,7 @@ struct timex {
long tolerance; /* clock frequency tolerance (ppm)
* (read only)
*/
- struct timeval time; /* (read only) */
+ struct timeval time; /* (read only, except for ADJ_SETOFFSET) */
long tick; /* (modified) usecs between clock ticks */

long ppsfreq; /* pps frequency (scaled ppm) (ro) */
@@ -101,6 +101,7 @@ struct timex {
#define ADJ_ESTERROR 0x0008 /* estimated time error */
#define ADJ_STATUS 0x0010 /* clock status */
#define ADJ_TIMECONST 0x0020 /* pll time constant */
+#define ADJ_SETOFFSET 0x0040 /* add 'time' to current time */
#define ADJ_TAI 0x0080 /* set TAI offset */
#define ADJ_MICRO 0x1000 /* select microsecond resolution */
#define ADJ_NANO 0x2000 /* select nanosecond resolution */
diff --git a/kernel/compat.c b/kernel/compat.c
index e167efc..f408ab5 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -52,6 +52,64 @@ static int compat_put_timeval(struct compat_timeval __user *o,
put_user(i->tv_usec, &o->tv_usec)) ? -EFAULT : 0;
}

+static int compat_get_timex(struct timex *txc, struct compat_timex __user *utp)
+{
+ memset(txc, 0, sizeof(struct timex));
+
+ if (!access_ok(VERIFY_READ, utp, sizeof(struct compat_timex)) ||
+ __get_user(txc->modes, &utp->modes) ||
+ __get_user(txc->offset, &utp->offset) ||
+ __get_user(txc->freq, &utp->freq) ||
+ __get_user(txc->maxerror, &utp->maxerror) ||
+ __get_user(txc->esterror, &utp->esterror) ||
+ __get_user(txc->status, &utp->status) ||
+ __get_user(txc->constant, &utp->constant) ||
+ __get_user(txc->precision, &utp->precision) ||
+ __get_user(txc->tolerance, &utp->tolerance) ||
+ __get_user(txc->time.tv_sec, &utp->time.tv_sec) ||
+ __get_user(txc->time.tv_usec, &utp->time.tv_usec) ||
+ __get_user(txc->tick, &utp->tick) ||
+ __get_user(txc->ppsfreq, &utp->ppsfreq) ||
+ __get_user(txc->jitter, &utp->jitter) ||
+ __get_user(txc->shift, &utp->shift) ||
+ __get_user(txc->stabil, &utp->stabil) ||
+ __get_user(txc->jitcnt, &utp->jitcnt) ||
+ __get_user(txc->calcnt, &utp->calcnt) ||
+ __get_user(txc->errcnt, &utp->errcnt) ||
+ __get_user(txc->stbcnt, &utp->stbcnt))
+ return -EFAULT;
+
+ return 0;
+}
+
+static int compat_put_timex(struct compat_timex __user *utp, struct timex *txc)
+{
+ if (!access_ok(VERIFY_WRITE, utp, sizeof(struct compat_timex)) ||
+ __put_user(txc->modes, &utp->modes) ||
+ __put_user(txc->offset, &utp->offset) ||
+ __put_user(txc->freq, &utp->freq) ||
+ __put_user(txc->maxerror, &utp->maxerror) ||
+ __put_user(txc->esterror, &utp->esterror) ||
+ __put_user(txc->status, &utp->status) ||
+ __put_user(txc->constant, &utp->constant) ||
+ __put_user(txc->precision, &utp->precision) ||
+ __put_user(txc->tolerance, &utp->tolerance) ||
+ __put_user(txc->time.tv_sec, &utp->time.tv_sec) ||
+ __put_user(txc->time.tv_usec, &utp->time.tv_usec) ||
+ __put_user(txc->tick, &utp->tick) ||
+ __put_user(txc->ppsfreq, &utp->ppsfreq) ||
+ __put_user(txc->jitter, &utp->jitter) ||
+ __put_user(txc->shift, &utp->shift) ||
+ __put_user(txc->stabil, &utp->stabil) ||
+ __put_user(txc->jitcnt, &utp->jitcnt) ||
+ __put_user(txc->calcnt, &utp->calcnt) ||
+ __put_user(txc->errcnt, &utp->errcnt) ||
+ __put_user(txc->stbcnt, &utp->stbcnt) ||
+ __put_user(txc->tai, &utp->tai))
+ return -EFAULT;
+ return 0;
+}
+
asmlinkage long compat_sys_gettimeofday(struct compat_timeval __user *tv,
struct timezone __user *tz)
{
@@ -617,6 +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)
{
@@ -951,58 +1032,17 @@ asmlinkage long compat_sys_rt_sigsuspend(compat_sigset_t __user *unewset, compat
asmlinkage long compat_sys_adjtimex(struct compat_timex __user *utp)
{
struct timex txc;
- int ret;
-
- memset(&txc, 0, sizeof(struct timex));
+ int err, ret;

- if (!access_ok(VERIFY_READ, utp, sizeof(struct compat_timex)) ||
- __get_user(txc.modes, &utp->modes) ||
- __get_user(txc.offset, &utp->offset) ||
- __get_user(txc.freq, &utp->freq) ||
- __get_user(txc.maxerror, &utp->maxerror) ||
- __get_user(txc.esterror, &utp->esterror) ||
- __get_user(txc.status, &utp->status) ||
- __get_user(txc.constant, &utp->constant) ||
- __get_user(txc.precision, &utp->precision) ||
- __get_user(txc.tolerance, &utp->tolerance) ||
- __get_user(txc.time.tv_sec, &utp->time.tv_sec) ||
- __get_user(txc.time.tv_usec, &utp->time.tv_usec) ||
- __get_user(txc.tick, &utp->tick) ||
- __get_user(txc.ppsfreq, &utp->ppsfreq) ||
- __get_user(txc.jitter, &utp->jitter) ||
- __get_user(txc.shift, &utp->shift) ||
- __get_user(txc.stabil, &utp->stabil) ||
- __get_user(txc.jitcnt, &utp->jitcnt) ||
- __get_user(txc.calcnt, &utp->calcnt) ||
- __get_user(txc.errcnt, &utp->errcnt) ||
- __get_user(txc.stbcnt, &utp->stbcnt))
- return -EFAULT;
+ err = compat_get_timex(&txc, utp);
+ if (err)
+ return err;

ret = do_adjtimex(&txc);

- if (!access_ok(VERIFY_WRITE, utp, sizeof(struct compat_timex)) ||
- __put_user(txc.modes, &utp->modes) ||
- __put_user(txc.offset, &utp->offset) ||
- __put_user(txc.freq, &utp->freq) ||
- __put_user(txc.maxerror, &utp->maxerror) ||
- __put_user(txc.esterror, &utp->esterror) ||
- __put_user(txc.status, &utp->status) ||
- __put_user(txc.constant, &utp->constant) ||
- __put_user(txc.precision, &utp->precision) ||
- __put_user(txc.tolerance, &utp->tolerance) ||
- __put_user(txc.time.tv_sec, &utp->time.tv_sec) ||
- __put_user(txc.time.tv_usec, &utp->time.tv_usec) ||
- __put_user(txc.tick, &utp->tick) ||
- __put_user(txc.ppsfreq, &utp->ppsfreq) ||
- __put_user(txc.jitter, &utp->jitter) ||
- __put_user(txc.shift, &utp->shift) ||
- __put_user(txc.stabil, &utp->stabil) ||
- __put_user(txc.jitcnt, &utp->jitcnt) ||
- __put_user(txc.calcnt, &utp->calcnt) ||
- __put_user(txc.errcnt, &utp->errcnt) ||
- __put_user(txc.stbcnt, &utp->stbcnt) ||
- __put_user(txc.tai, &utp->tai))
- ret = -EFAULT;
+ err = compat_put_timex(utp, &txc);
+ if (err)
+ return err;

return ret;
}
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 6842eeb..e1c2e7b 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -207,6 +207,10 @@ int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
return error;
}

+int posix_cpu_clock_adj(const clockid_t which_clock, struct timex *tx)
+{
+ return -EOPNOTSUPP;
+}

/*
* Sample a per-thread clock for the given task.
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 9ca4973..67fba5c 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -132,6 +132,8 @@ static DEFINE_SPINLOCK(idr_lock);
*/

static struct k_clock posix_clocks[MAX_CLOCKS];
+static DECLARE_BITMAP(clocks_map, MAX_CLOCKS);
+static DEFINE_MUTEX(clocks_mux); /* protects 'posix_clocks' and 'clocks_map' */

/*
* These ones are defined below.
@@ -197,6 +199,14 @@ static int common_timer_create(struct k_itimer *new_timer)
return 0;
}

+static inline int common_clock_adj(const clockid_t which_clock, struct timex *t)
+{
+ if (CLOCK_REALTIME == which_clock)
+ return do_adjtimex(t);
+ else
+ return -EOPNOTSUPP;
+}
+
static int no_timer_create(struct k_itimer *new_timer)
{
return -EOPNOTSUPP;
@@ -476,18 +486,43 @@ static struct pid *good_sigevent(sigevent_t * event)
return task_pid(rtn);
}

-void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock)
+int register_posix_clock(const clockid_t id, struct k_clock *clock)
{
- if ((unsigned) clock_id >= MAX_CLOCKS) {
- printk("POSIX clock register failed for clock_id %d\n",
- clock_id);
- return;
- }
+ struct k_clock *kc;
+ int err = 0;

- posix_clocks[clock_id] = *new_clock;
+ mutex_lock(&clocks_mux);
+ if (test_bit(id, clocks_map)) {
+ pr_err("clock_id %d already registered\n", id);
+ err = -EBUSY;
+ goto out;
+ }
+ kc = &posix_clocks[id];
+ *kc = *clock;
+ kc->id = id;
+ set_bit(id, clocks_map);
+out:
+ mutex_unlock(&clocks_mux);
+ return err;
}
EXPORT_SYMBOL_GPL(register_posix_clock);

+clockid_t create_posix_clock(struct k_clock *clock)
+{
+ clockid_t id;
+
+ mutex_lock(&clocks_mux);
+ id = find_first_zero_bit(clocks_map, MAX_CLOCKS);
+ mutex_unlock(&clocks_mux);
+
+ if (id < MAX_CLOCKS) {
+ register_posix_clock(id, clock);
+ return id;
+ }
+ return CLOCK_INVALID;
+}
+EXPORT_SYMBOL_GPL(create_posix_clock);
+
static struct k_itimer * alloc_posix_timer(void)
{
struct k_itimer *tmr;
@@ -969,6 +1004,15 @@ SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,

}

+SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
+ struct timex __user *, tx)
+{
+ if (invalid_clockid(which_clock))
+ return -EINVAL;
+
+ return CLOCK_DISPATCH(which_clock, clock_adj, (which_clock, tx));
+}
+
SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
struct timespec __user *, tp)
{
--
1.7.0.4