Mach messages: clock

Message catalog and dispatch · All subsystem ranges · Kernel entry map

osfmk/mach/clock.defs. Listed in the kernel kobject subsystem table, subject to the registration guards and per-slot skips. The destination's typed capability still controls admission. Registration evidence: mig_e.

Reading these entries

IDs are computed from the explicit preprocessing profiles in the catalog guide, counting both routines and skip slots. They are not discovered from a running kernel. Each entry retains all observed names/declaration locations; the displayed fields come from the first non-skipped profile. Alternative declarations can have different fields. simpleroutine is one-way at the MIG interface level.

An interface contract block quotes the adjacent local .defs comment with whitespace normalized. Mechanism paragraphs explain selected implementation decisions. Local body links and call names identify implementation evidence; syntactic call lists are reading aids, not a proof that every listed call executes on every path. Short complete implementation bodies are included where especially useful.

Complete routine and reserved-slot catalog

1000: clock_get_time

Interface contract:

Get the clock time. Available to all.

Mechanism: Rejects a null clock, then calls that clock’s c_gettime operation. The system-clock implementation converts system nanoseconds into mach_timespec_t; the calendar implementation uses calendar nanoseconds instead. The destination clock object selects the time domain, rather than a caller-supplied flavor. clock_get_time.

Declarations: clock_get_time (server64, server32, client64, client32, libsyscall64, sender64, local64).

Fields after preprocessing (server64):

routine clock_get_time(
  clock_serv : clock_serv_t;
 out cur_time : mach_timespec_t);

Local body: clock_get_time.

Implementation excerpt:

clock_get_time(
	clock_t                 clock,
	mach_timespec_t *cur_time)      /* OUT */
{
	if (clock == CLOCK_NULL) {
		return KERN_INVALID_ARGUMENT;
	}
	return (*clock->cl_ops->c_gettime)(cur_time);
}

1001: clock_get_attributes

Interface contract:

Get clock attributes. Available to all.

Mechanism: Requires a clock object and an installed c_getattr callback. The supplied clocks require exactly one output word. System-clock resolution and alarm-resolution flavors return a 10 ms value; the calendar clock reports the same time resolution but zero alarm resolution. Unknown flavors return KERN_INVALID_VALUE; a missing operation returns KERN_FAILURE. clock_get_attributes.

Declarations: clock_get_attributes (server64, server32, client64, client32, libsyscall64, sender64, local64).

Fields after preprocessing (server64):

routine clock_get_attributes(
  clock_serv : clock_serv_t;
 in flavor : clock_flavor_t;
 out clock_attr : clock_attr_t, CountInOut);

Local body: clock_get_attributes. Calls visible in this body include c_getattr.

Implementation excerpt:

clock_get_attributes(
	clock_t                                 clock,
	clock_flavor_t                  flavor,
	clock_attr_t                    attr,           /* OUT */
	mach_msg_type_number_t  *count)         /* IN/OUT */
{
	if (clock == CLOCK_NULL) {
		return KERN_INVALID_ARGUMENT;
	}
	if (clock->cl_ops->c_getattr) {
		return clock->cl_ops->c_getattr(flavor, attr, count);
	}
	return KERN_FAILURE;
}

1002: clock_alarm

Interface contract:

Setup a clock alarm. Available to all.

Mechanism: Only the system clock is supported. A missing reply capability fails immediately; an invalid or already-due time instead produces an immediate alarm reply and returns RPC success. Future alarms take a recycled or newly allocated record under the alarm lock, store the reply right, deadline and sequence number, then enter the ordered alarm machinery. Allocation drops and reacquires the lock. clock_alarm.

Declarations: clock_alarm (server64, server32, client64, client32, libsyscall64, sender64, local64).

Fields after preprocessing (server64):

routine clock_alarm(
  clock_serv : clock_serv_t;
  alarm_type : alarm_type_t;
  alarm_time : mach_timespec_t;
                alarm_port : clock_reply_t =
   MACH_MSG_TYPE_MAKE_SEND_ONCE|polymorphic);

Local body: clock_alarm. Calls visible in this body include IP_VALID, check_time, clock_alarm_reply, LOCK_ALARM, UNLOCK_ALARM, zalloc_flags, post_alarm.