File: /usr/src/linux/kernel/time.c
1 /*
2 * linux/kernel/time.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * This file contains the interface functions for the various
7 * time related system calls: time, stime, gettimeofday, settimeofday,
8 * adjtime
9 */
10 /*
11 * Modification history kernel/time.c
12 *
13 * 1993-09-02 Philip Gladstone
14 * Created file with time related functions from sched.c and adjtimex()
15 * 1993-10-08 Torsten Duwe
16 * adjtime interface update and CMOS clock write code
17 * 1995-08-13 Torsten Duwe
18 * kernel PLL updated to 1994-12-13 specs (rfc-1589)
19 * 1999-01-16 Ulrich Windl
20 * Introduced error checking for many cases in adjtimex().
21 * Updated NTP code according to technical memorandum Jan '96
22 * "A Kernel Model for Precision Timekeeping" by Dave Mills
23 * Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
24 * (Even though the technical memorandum forbids it)
25 */
26
27 #include <linux/mm.h>
28 #include <linux/timex.h>
29 #include <linux/smp_lock.h>
30
31 #include <asm/uaccess.h>
32
33 /*
34 * The timezone where the local system is located. Used as a default by some
35 * programs who obtain this value by using gettimeofday.
36 */
37 struct timezone sys_tz;
38
39 static void do_normal_gettime(struct timeval * tm)
40 {
41 *tm=xtime;
42 }
43
44 void (*do_get_fast_time)(struct timeval *) = do_normal_gettime;
45
46 /*
47 * Generic way to access 'xtime' (the current time of day).
48 * This can be changed if the platform provides a more accurate (and fast!)
49 * version.
50 */
51
52 void get_fast_time(struct timeval * t)
53 {
54 do_get_fast_time(t);
55 }
56
57 /* The xtime_lock is not only serializing the xtime read/writes but it's also
58 serializing all accesses to the global NTP variables now. */
59 extern rwlock_t xtime_lock;
60
61 #if !defined(__alpha__) && !defined(__ia64__)
62
63 /*
64 * sys_time() can be implemented in user-level using
65 * sys_gettimeofday(). Is this for backwards compatibility? If so,
66 * why not move it into the appropriate arch directory (for those
67 * architectures that need it).
68 *
69 * XXX This function is NOT 64-bit clean!
70 */
71 asmlinkage long sys_time(int * tloc)
72 {
73 int i;
74
75 /* SMP: This is fairly trivial. We grab CURRENT_TIME and
76 stuff it to user space. No side effects */
77 i = CURRENT_TIME;
78 if (tloc) {
79 if (put_user(i,tloc))
80 i = -EFAULT;
81 }
82 return i;
83 }
84
85 /*
86 * sys_stime() can be implemented in user-level using
87 * sys_settimeofday(). Is this for backwards compatibility? If so,
88 * why not move it into the appropriate arch directory (for those
89 * architectures that need it).
90 */
91
92 asmlinkage long sys_stime(int * tptr)
93 {
94 int value;
95
96 if (!capable(CAP_SYS_TIME))
97 return -EPERM;
98 if (get_user(value, tptr))
99 return -EFAULT;
100 write_lock_irq(&xtime_lock);
101 xtime.tv_sec = value;
102 xtime.tv_usec = 0;
103 time_adjust = 0; /* stop active adjtime() */
104 time_status |= STA_UNSYNC;
105 time_maxerror = NTP_PHASE_LIMIT;
106 time_esterror = NTP_PHASE_LIMIT;
107 write_unlock_irq(&xtime_lock);
108 return 0;
109 }
110
111 #endif
112
113 asmlinkage long sys_gettimeofday(struct timeval *tv, struct timezone *tz)
114 {
115 if (tv) {
116 struct timeval ktv;
117 do_gettimeofday(&ktv);
118 if (copy_to_user(tv, &ktv, sizeof(ktv)))
119 return -EFAULT;
120 }
121 if (tz) {
122 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
123 return -EFAULT;
124 }
125 return 0;
126 }
127
128 /*
129 * Adjust the time obtained from the CMOS to be UTC time instead of
130 * local time.
131 *
132 * This is ugly, but preferable to the alternatives. Otherwise we
133 * would either need to write a program to do it in /etc/rc (and risk
134 * confusion if the program gets run more than once; it would also be
135 * hard to make the program warp the clock precisely n hours) or
136 * compile in the timezone information into the kernel. Bad, bad....
137 *
138 * - TYT, 1992-01-01
139 *
140 * The best thing to do is to keep the CMOS clock in universal time (UTC)
141 * as real UNIX machines always do it. This avoids all headaches about
142 * daylight saving times and warping kernel clocks.
143 */
144 inline static void warp_clock(void)
145 {
146 write_lock_irq(&xtime_lock);
147 xtime.tv_sec += sys_tz.tz_minuteswest * 60;
148 write_unlock_irq(&xtime_lock);
149 }
150
151 /*
152 * In case for some reason the CMOS clock has not already been running
153 * in UTC, but in some local time: The first time we set the timezone,
154 * we will warp the clock so that it is ticking UTC time instead of
155 * local time. Presumably, if someone is setting the timezone then we
156 * are running in an environment where the programs understand about
157 * timezones. This should be done at boot time in the /etc/rc script,
158 * as soon as possible, so that the clock can be set right. Otherwise,
159 * various programs will get confused when the clock gets warped.
160 */
161
162 int do_sys_settimeofday(struct timeval *tv, struct timezone *tz)
163 {
164 static int firsttime = 1;
165
166 if (!capable(CAP_SYS_TIME))
167 return -EPERM;
168
169 if (tz) {
170 /* SMP safe, global irq locking makes it work. */
171 sys_tz = *tz;
172 if (firsttime) {
173 firsttime = 0;
174 if (!tv)
175 warp_clock();
176 }
177 }
178 if (tv)
179 {
180 /* SMP safe, again the code in arch/foo/time.c should
181 * globally block out interrupts when it runs.
182 */
183 do_settimeofday(tv);
184 }
185 return 0;
186 }
187
188 asmlinkage long sys_settimeofday(struct timeval *tv, struct timezone *tz)
189 {
190 struct timeval new_tv;
191 struct timezone new_tz;
192
193 if (tv) {
194 if (copy_from_user(&new_tv, tv, sizeof(*tv)))
195 return -EFAULT;
196 }
197 if (tz) {
198 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
199 return -EFAULT;
200 }
201
202 return do_sys_settimeofday(tv ? &new_tv : NULL, tz ? &new_tz : NULL);
203 }
204
205 long pps_offset; /* pps time offset (us) */
206 long pps_jitter = MAXTIME; /* time dispersion (jitter) (us) */
207
208 long pps_freq; /* frequency offset (scaled ppm) */
209 long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */
210
211 long pps_valid = PPS_VALID; /* pps signal watchdog counter */
212
213 int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */
214
215 long pps_jitcnt; /* jitter limit exceeded */
216 long pps_calcnt; /* calibration intervals */
217 long pps_errcnt; /* calibration errors */
218 long pps_stbcnt; /* stability limit exceeded */
219
220 /* hook for a loadable hardpps kernel module */
221 void (*hardpps_ptr)(struct timeval *);
222
223 /* adjtimex mainly allows reading (and writing, if superuser) of
224 * kernel time-keeping variables. used by xntpd.
225 */
226 int do_adjtimex(struct timex *txc)
227 {
228 long ltemp, mtemp, save_adjust;
229 int result;
230
231 /* In order to modify anything, you gotta be super-user! */
232 if (txc->modes && !capable(CAP_SYS_TIME))
233 return -EPERM;
234
235 /* Now we validate the data before disabling interrupts */
236
237 if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
238 /* adjustment Offset limited to +- .512 seconds */
239 if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
240 return -EINVAL;
241
242 /* if the quartz is off by more than 10% something is VERY wrong ! */
243 if (txc->modes & ADJ_TICK)
244 if (txc->tick < 900000/HZ || txc->tick > 1100000/HZ)
245 return -EINVAL;
246
247 write_lock_irq(&xtime_lock);
248 result = time_state; /* mostly `TIME_OK' */
249
250 /* Save for later - semantics of adjtime is to return old value */
251 save_adjust = time_adjust;
252
253 #if 0 /* STA_CLOCKERR is never set yet */
254 time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
255 #endif
256 /* If there are input parameters, then process them */
257 if (txc->modes)
258 {
259 if (txc->modes & ADJ_STATUS) /* only set allowed bits */
260 time_status = (txc->status & ~STA_RONLY) |
261 (time_status & STA_RONLY);
262
263 if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */
264 if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
265 result = -EINVAL;
266 goto leave;
267 }
268 time_freq = txc->freq - pps_freq;
269 }
270
271 if (txc->modes & ADJ_MAXERROR) {
272 if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
273 result = -EINVAL;
274 goto leave;
275 }
276 time_maxerror = txc->maxerror;
277 }
278
279 if (txc->modes & ADJ_ESTERROR) {
280 if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
281 result = -EINVAL;
282 goto leave;
283 }
284 time_esterror = txc->esterror;
285 }
286
287 if (txc->modes & ADJ_TIMECONST) { /* p. 24 */
288 if (txc->constant < 0) { /* NTP v4 uses values > 6 */
289 result = -EINVAL;
290 goto leave;
291 }
292 time_constant = txc->constant;
293 }
294
295 if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
296 if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
297 /* adjtime() is independent from ntp_adjtime() */
298 time_adjust = txc->offset;
299 }
300 else if ( time_status & (STA_PLL | STA_PPSTIME) ) {
301 ltemp = (time_status & (STA_PPSTIME | STA_PPSSIGNAL)) ==
302 (STA_PPSTIME | STA_PPSSIGNAL) ?
303 pps_offset : txc->offset;
304
305 /*
306 * Scale the phase adjustment and
307 * clamp to the operating range.
308 */
309 if (ltemp > MAXPHASE)
310 time_offset = MAXPHASE << SHIFT_UPDATE;
311 else if (ltemp < -MAXPHASE)
312 time_offset = -(MAXPHASE << SHIFT_UPDATE);
313 else
314 time_offset = ltemp << SHIFT_UPDATE;
315
316 /*
317 * Select whether the frequency is to be controlled
318 * and in which mode (PLL or FLL). Clamp to the operating
319 * range. Ugly multiply/divide should be replaced someday.
320 */
321
322 if (time_status & STA_FREQHOLD || time_reftime == 0)
323 time_reftime = xtime.tv_sec;
324 mtemp = xtime.tv_sec - time_reftime;
325 time_reftime = xtime.tv_sec;
326 if (time_status & STA_FLL) {
327 if (mtemp >= MINSEC) {
328 ltemp = (time_offset / mtemp) << (SHIFT_USEC -
329 SHIFT_UPDATE);
330 if (ltemp < 0)
331 time_freq -= -ltemp >> SHIFT_KH;
332 else
333 time_freq += ltemp >> SHIFT_KH;
334 } else /* calibration interval too short (p. 12) */
335 result = TIME_ERROR;
336 } else { /* PLL mode */
337 if (mtemp < MAXSEC) {
338 ltemp *= mtemp;
339 if (ltemp < 0)
340 time_freq -= -ltemp >> (time_constant +
341 time_constant +
342 SHIFT_KF - SHIFT_USEC);
343 else
344 time_freq += ltemp >> (time_constant +
345 time_constant +
346 SHIFT_KF - SHIFT_USEC);
347 } else /* calibration interval too long (p. 12) */
348 result = TIME_ERROR;
349 }
350 if (time_freq > time_tolerance)
351 time_freq = time_tolerance;
352 else if (time_freq < -time_tolerance)
353 time_freq = -time_tolerance;
354 } /* STA_PLL || STA_PPSTIME */
355 } /* txc->modes & ADJ_OFFSET */
356 if (txc->modes & ADJ_TICK) {
357 /* if the quartz is off by more than 10% something is
358 VERY wrong ! */
359 if (txc->tick < 900000/HZ || txc->tick > 1100000/HZ) {
360 result = -EINVAL;
361 goto leave;
362 }
363 tick = txc->tick;
364 }
365 } /* txc->modes */
366 leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0
367 || ((time_status & (STA_PPSFREQ|STA_PPSTIME)) != 0
368 && (time_status & STA_PPSSIGNAL) == 0)
369 /* p. 24, (b) */
370 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
371 == (STA_PPSTIME|STA_PPSJITTER))
372 /* p. 24, (c) */
373 || ((time_status & STA_PPSFREQ) != 0
374 && (time_status & (STA_PPSWANDER|STA_PPSERROR)) != 0))
375 /* p. 24, (d) */
376 result = TIME_ERROR;
377
378 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
379 txc->offset = save_adjust;
380 else {
381 if (time_offset < 0)
382 txc->offset = -(-time_offset >> SHIFT_UPDATE);
383 else
384 txc->offset = time_offset >> SHIFT_UPDATE;
385 }
386 txc->freq = time_freq + pps_freq;
387 txc->maxerror = time_maxerror;
388 txc->esterror = time_esterror;
389 txc->status = time_status;
390 txc->constant = time_constant;
391 txc->precision = time_precision;
392 txc->tolerance = time_tolerance;
393 txc->tick = tick;
394 txc->ppsfreq = pps_freq;
395 txc->jitter = pps_jitter >> PPS_AVG;
396 txc->shift = pps_shift;
397 txc->stabil = pps_stabil;
398 txc->jitcnt = pps_jitcnt;
399 txc->calcnt = pps_calcnt;
400 txc->errcnt = pps_errcnt;
401 txc->stbcnt = pps_stbcnt;
402 write_unlock_irq(&xtime_lock);
403 do_gettimeofday(&txc->time);
404 return(result);
405 }
406
407 asmlinkage long sys_adjtimex(struct timex *txc_p)
408 {
409 struct timex txc; /* Local copy of parameter */
410 int ret;
411
412 /* Copy the user data space into the kernel copy
413 * structure. But bear in mind that the structures
414 * may change
415 */
416 if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
417 return -EFAULT;
418 ret = do_adjtimex(&txc);
419 return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
420 }
421