7b6435b2b8
On NetBSD programs with write access to /dev/clockctl can adjust or set the system clock without the root privileges. Add a function to drop the privileges and check if the process has write access to the device to get a more descriptive error message when the chrony uid/gid doesn't match the owner of the device.
352 lines
8.3 KiB
C
352 lines
8.3 KiB
C
/*
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chronyd/chronyc - Programs for keeping computer clocks accurate.
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**********************************************************************
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* Copyright (C) Richard P. Curnow 1997-2001
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* Copyright (C) J. Hannken-Illjes 2001
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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**********************************************************************
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=======================================================================
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Driver file for the NetBSD operating system.
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*/
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#include "config.h"
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#ifdef NETBSD
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#include <kvm.h>
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#include <nlist.h>
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#include <fcntl.h>
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#include <assert.h>
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#include <sys/time.h>
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#include <stdio.h>
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#include <signal.h>
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#include "sys_netbsd.h"
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#include "localp.h"
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#include "logging.h"
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#include "util.h"
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/* ================================================== */
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/* This register contains the number of seconds by which the local
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clock was estimated to be fast of reference time at the epoch when
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gettimeofday() returned T0 */
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static double offset_register;
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/* This register contains the epoch to which the offset is referenced */
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static struct timeval T0;
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/* This register contains the current estimate of the system
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frequency, in absolute (NOT ppm) */
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static double current_freq;
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/* This register contains the number of seconds of adjustment that
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were passed to adjtime last time it was called. */
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static double adjustment_requested;
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/* Kernel parameters to calculate adjtime error. */
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static int kern_tickadj;
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static long kern_bigadj;
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/* ================================================== */
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static void
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clock_initialise(void)
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{
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struct timeval newadj, oldadj;
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offset_register = 0.0;
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adjustment_requested = 0.0;
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current_freq = 0.0;
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if (gettimeofday(&T0, NULL) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "gettimeofday() failed");
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}
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newadj.tv_sec = 0;
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newadj.tv_usec = 0;
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if (adjtime(&newadj, &oldadj) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "adjtime() failed");
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}
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}
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/* ================================================== */
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static void
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clock_finalise(void)
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{
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/* Nothing to do yet */
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}
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/* ================================================== */
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static void
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start_adjust(void)
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{
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struct timeval newadj, oldadj;
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struct timeval T1;
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double elapsed, accrued_error;
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double adjust_required;
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struct timeval exact_newadj;
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long delta, tickdelta;
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double rounding_error;
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double old_adjust_remaining;
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/* Determine the amount of error built up since the last adjustment */
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if (gettimeofday(&T1, NULL) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "gettimeofday() failed");
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}
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UTI_DiffTimevalsToDouble(&elapsed, &T1, &T0);
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accrued_error = elapsed * current_freq;
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adjust_required = - (accrued_error + offset_register);
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UTI_DoubleToTimeval(adjust_required, &exact_newadj);
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/* At this point, we need to round the required adjustment the
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same way the kernel does. */
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delta = exact_newadj.tv_sec * 1000000 + exact_newadj.tv_usec;
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if (delta > kern_bigadj || delta < -kern_bigadj)
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tickdelta = 10 * kern_tickadj;
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else
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tickdelta = kern_tickadj;
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if (delta % tickdelta)
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delta = delta / tickdelta * tickdelta;
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newadj.tv_sec = 0;
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newadj.tv_usec = delta;
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UTI_NormaliseTimeval(&newadj);
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/* Add rounding error back onto offset register. */
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UTI_DiffTimevalsToDouble(&rounding_error, &newadj, &exact_newadj);
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if (adjtime(&newadj, &oldadj) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "adjtime() failed");
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}
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UTI_TimevalToDouble(&oldadj, &old_adjust_remaining);
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offset_register = rounding_error - old_adjust_remaining;
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T0 = T1;
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UTI_TimevalToDouble(&newadj, &adjustment_requested);
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}
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/* ================================================== */
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static void
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stop_adjust(void)
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{
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struct timeval T1;
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struct timeval zeroadj, remadj;
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double adjustment_remaining, adjustment_achieved;
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double elapsed, elapsed_plus_adjust;
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zeroadj.tv_sec = 0;
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zeroadj.tv_usec = 0;
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if (adjtime(&zeroadj, &remadj) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "adjtime() failed");
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}
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if (gettimeofday(&T1, NULL) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "gettimeofday() failed");
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}
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UTI_DiffTimevalsToDouble(&elapsed, &T1, &T0);
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UTI_TimevalToDouble(&remadj, &adjustment_remaining);
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adjustment_achieved = adjustment_requested - adjustment_remaining;
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elapsed_plus_adjust = elapsed - adjustment_achieved;
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offset_register += current_freq * elapsed_plus_adjust - adjustment_remaining;
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adjustment_requested = 0.0;
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T0 = T1;
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}
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/* ================================================== */
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/* Positive offset means system clock is fast of true time, therefore
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slew backwards */
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static void
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accrue_offset(double offset, double corr_rate)
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{
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stop_adjust();
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offset_register += offset;
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start_adjust();
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}
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/* ================================================== */
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/* Positive offset means system clock is fast of true time, therefore
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step backwards */
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static int
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apply_step_offset(double offset)
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{
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struct timeval old_time, new_time, T1;
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stop_adjust();
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if (gettimeofday(&old_time, NULL) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "gettimeofday() failed");
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}
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UTI_AddDoubleToTimeval(&old_time, -offset, &new_time);
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if (settimeofday(&new_time, NULL) < 0) {
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DEBUG_LOG(LOGF_SysNetBSD, "settimeofday() failed");
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return 0;
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}
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UTI_AddDoubleToTimeval(&T0, offset, &T1);
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T0 = T1;
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start_adjust();
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return 1;
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}
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/* ================================================== */
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static double
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set_frequency(double new_freq_ppm)
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{
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stop_adjust();
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current_freq = new_freq_ppm * 1.0e-6;
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start_adjust();
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return current_freq * 1.0e6;
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}
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/* ================================================== */
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static double
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read_frequency(void)
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{
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return current_freq * 1.0e6;
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}
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/* ================================================== */
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static void
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get_offset_correction(struct timeval *raw,
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double *corr, double *err)
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{
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stop_adjust();
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*corr = -offset_register;
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start_adjust();
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if (err)
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*err = 0.0;
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}
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/* ================================================== */
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void
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SYS_NetBSD_Initialise(void)
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{
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static struct nlist nl[] = {
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{"_tickadj"},
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{"_bigadj"},
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{NULL}
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};
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kvm_t *kt;
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kt = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL);
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if (!kt) {
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LOG_FATAL(LOGF_SysNetBSD, "Cannot open kvm");
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}
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if (kvm_nlist(kt, nl) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "Cannot read kernel symbols");
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}
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if (kvm_read(kt, nl[0].n_value, (char *)(&kern_tickadj), sizeof(int)) < 0) {
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LOG_FATAL(LOGF_SysNetBSD, "Cannot read from _tickadj");
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}
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if (kvm_read(kt, nl[1].n_value, (char *)(&kern_bigadj), sizeof(long)) < 0) {
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/* kernel doesn't have the symbol, use one second instead */
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kern_bigadj = 1000000;
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}
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kvm_close(kt);
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clock_initialise();
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lcl_RegisterSystemDrivers(read_frequency, set_frequency,
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accrue_offset, apply_step_offset,
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get_offset_correction,
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NULL /* set_leap */,
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NULL /* set_sync_status */);
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}
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/* ================================================== */
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void
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SYS_NetBSD_Finalise(void)
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{
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clock_finalise();
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}
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/* ================================================== */
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#ifdef FEAT_PRIVDROP
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void
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SYS_NetBSD_DropRoot(uid_t uid, gid_t gid)
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{
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int fd;
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if (setgroups(0, NULL))
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LOG_FATAL(LOGF_SysNetBSD, "setgroups() failed : %s", strerror(errno));
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if (setgid(gid))
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LOG_FATAL(LOGF_SysNetBSD, "setgid(%d) failed : %s", gid, strerror(errno));
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if (setuid(uid))
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LOG_FATAL(LOGF_SysNetBSD, "setuid(%d) failed : %s", uid, strerror(errno));
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DEBUG_LOG(LOGF_SysNetBSD, "Root dropped to uid %d gid %d", uid, gid);
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/* Check if we have write access to /dev/clockctl */
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fd = open("/dev/clockctl", O_WRONLY);
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if (fd < 0)
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LOG_FATAL(LOGF_SysNetBSD, "Can't write to /dev/clockctl");
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close(fd);
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}
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#endif
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#endif /* NETBSD */
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