clockctl(4) - NetBSD Manual Pages

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CLOCKCTL(4)             NetBSD Kernel Interfaces Manual            CLOCKCTL(4)


NAME

     clockctl -- Clock subsystem user control


SYNOPSIS

     pseudo-device clockctl


DESCRIPTION

     The clockctl interface brings clock control to non-root users. Any user
     with write access to /dev/clockctl will be able to perform operations
     such as settimeofday(2), clock_settime(2), adjtime(2), or ntp_adjtime(2),
     which are normally restricted to the super-user. Using the clockctl
     pseudo-device, it is possible to run daemons such as ntpd(8) as non-priv-
     ileged users, thus reducing the security exposure if a compromise is
     found in such a daemon.

     The clockctl pseudo-device driver provides an ioctl(2) call for each
     privileged clock-related system call. The system call stubs in C library
     will use the ioctl(2) on /dev/clockctl if the special file is present and
     accessible, or will revert to the plain super-user-restricted system call
     if the special file is not accessible.

     The following ioctl(2) calls are defined in <sys/clockctl.h>:

     CLOCKCTL_SETTIMEOFDAY
               This will run the settimeofday(2) system call. Argument should
               be a pointer to a struct clockctl_settimeofday_args:

               struct clockctl_settimeofday_args {
                   struct timeval tv;
                   struct timezone tzp;
               };

     CLOCKCTL_CLOCK_SETTIME
               This will run the clock_settime(2) system call. Argument should
               be a pointer to a struct clockctl_clock_settime_args:

               struct clockctl_clock_settime_args {
                   clockid_t clock_id;
                   struct timespec tp;
               };

     CLOCKCTL_ADJTIME
               This will run the adjtime(2) system call. Argument should be a
               pointer to a struct clockctl_adjtime_args:

               struct clockctl_adjtime_args {
                   struct timeval delta;
                   struct timeval olddelta;
               };

     CLOCKCTL_NTP_ADJTIME
               This will run the ntp_adjtime(2) system call. Argument should
               be a pointer to a struct clockctl_ntp_adjtime_args:

               struct clockctl_ntp_adjtime_args {
                   struct timex tp;
               };


SEE ALSO

     adjtime(2), clock_settime(2), ioctl(2), settimeofday(2)


HISTORY

     clockctl appeared in NetBSD 1.6.

NetBSD 4.0                     October 20, 2001                     NetBSD 4.0