xref: /openbmc/linux/lib/vdso/gettimeofday.c (revision 808094fc)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Generic userspace implementations of gettimeofday() and similar.
4  */
5 #include <vdso/datapage.h>
6 #include <vdso/helpers.h>
7 
8 #ifndef vdso_calc_delta
9 /*
10  * Default implementation which works for all sane clocksources. That
11  * obviously excludes x86/TSC.
12  */
13 static __always_inline
vdso_calc_delta(u64 cycles,u64 last,u64 mask,u32 mult)14 u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
15 {
16 	return ((cycles - last) & mask) * mult;
17 }
18 #endif
19 
20 #ifndef vdso_shift_ns
vdso_shift_ns(u64 ns,u32 shift)21 static __always_inline u64 vdso_shift_ns(u64 ns, u32 shift)
22 {
23 	return ns >> shift;
24 }
25 #endif
26 
27 #ifndef __arch_vdso_hres_capable
__arch_vdso_hres_capable(void)28 static inline bool __arch_vdso_hres_capable(void)
29 {
30 	return true;
31 }
32 #endif
33 
34 #ifndef vdso_clocksource_ok
vdso_clocksource_ok(const struct vdso_data * vd)35 static inline bool vdso_clocksource_ok(const struct vdso_data *vd)
36 {
37 	return vd->clock_mode != VDSO_CLOCKMODE_NONE;
38 }
39 #endif
40 
41 #ifndef vdso_cycles_ok
vdso_cycles_ok(u64 cycles)42 static inline bool vdso_cycles_ok(u64 cycles)
43 {
44 	return true;
45 }
46 #endif
47 
48 #ifdef CONFIG_TIME_NS
do_hres_timens(const struct vdso_data * vdns,clockid_t clk,struct __kernel_timespec * ts)49 static __always_inline int do_hres_timens(const struct vdso_data *vdns, clockid_t clk,
50 					  struct __kernel_timespec *ts)
51 {
52 	const struct vdso_data *vd;
53 	const struct timens_offset *offs = &vdns->offset[clk];
54 	const struct vdso_timestamp *vdso_ts;
55 	u64 cycles, last, ns;
56 	u32 seq;
57 	s64 sec;
58 
59 	vd = vdns - (clk == CLOCK_MONOTONIC_RAW ? CS_RAW : CS_HRES_COARSE);
60 	vd = __arch_get_timens_vdso_data(vd);
61 	if (clk != CLOCK_MONOTONIC_RAW)
62 		vd = &vd[CS_HRES_COARSE];
63 	else
64 		vd = &vd[CS_RAW];
65 	vdso_ts = &vd->basetime[clk];
66 
67 	do {
68 		seq = vdso_read_begin(vd);
69 
70 		if (unlikely(!vdso_clocksource_ok(vd)))
71 			return -1;
72 
73 		cycles = __arch_get_hw_counter(vd->clock_mode, vd);
74 		if (unlikely(!vdso_cycles_ok(cycles)))
75 			return -1;
76 		ns = vdso_ts->nsec;
77 		last = vd->cycle_last;
78 		ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
79 		ns = vdso_shift_ns(ns, vd->shift);
80 		sec = vdso_ts->sec;
81 	} while (unlikely(vdso_read_retry(vd, seq)));
82 
83 	/* Add the namespace offset */
84 	sec += offs->sec;
85 	ns += offs->nsec;
86 
87 	/*
88 	 * Do this outside the loop: a race inside the loop could result
89 	 * in __iter_div_u64_rem() being extremely slow.
90 	 */
91 	ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
92 	ts->tv_nsec = ns;
93 
94 	return 0;
95 }
96 #else
97 static __always_inline
__arch_get_timens_vdso_data(const struct vdso_data * vd)98 const struct vdso_data *__arch_get_timens_vdso_data(const struct vdso_data *vd)
99 {
100 	return NULL;
101 }
102 
do_hres_timens(const struct vdso_data * vdns,clockid_t clk,struct __kernel_timespec * ts)103 static __always_inline int do_hres_timens(const struct vdso_data *vdns, clockid_t clk,
104 					  struct __kernel_timespec *ts)
105 {
106 	return -EINVAL;
107 }
108 #endif
109 
do_hres(const struct vdso_data * vd,clockid_t clk,struct __kernel_timespec * ts)110 static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk,
111 				   struct __kernel_timespec *ts)
112 {
113 	const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
114 	u64 cycles, last, sec, ns;
115 	u32 seq;
116 
117 	/* Allows to compile the high resolution parts out */
118 	if (!__arch_vdso_hres_capable())
119 		return -1;
120 
121 	do {
122 		/*
123 		 * Open coded to handle VDSO_CLOCKMODE_TIMENS. Time namespace
124 		 * enabled tasks have a special VVAR page installed which
125 		 * has vd->seq set to 1 and vd->clock_mode set to
126 		 * VDSO_CLOCKMODE_TIMENS. For non time namespace affected tasks
127 		 * this does not affect performance because if vd->seq is
128 		 * odd, i.e. a concurrent update is in progress the extra
129 		 * check for vd->clock_mode is just a few extra
130 		 * instructions while spin waiting for vd->seq to become
131 		 * even again.
132 		 */
133 		while (unlikely((seq = READ_ONCE(vd->seq)) & 1)) {
134 			if (IS_ENABLED(CONFIG_TIME_NS) &&
135 			    vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
136 				return do_hres_timens(vd, clk, ts);
137 			cpu_relax();
138 		}
139 		smp_rmb();
140 
141 		if (unlikely(!vdso_clocksource_ok(vd)))
142 			return -1;
143 
144 		cycles = __arch_get_hw_counter(vd->clock_mode, vd);
145 		if (unlikely(!vdso_cycles_ok(cycles)))
146 			return -1;
147 		ns = vdso_ts->nsec;
148 		last = vd->cycle_last;
149 		ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
150 		ns = vdso_shift_ns(ns, vd->shift);
151 		sec = vdso_ts->sec;
152 	} while (unlikely(vdso_read_retry(vd, seq)));
153 
154 	/*
155 	 * Do this outside the loop: a race inside the loop could result
156 	 * in __iter_div_u64_rem() being extremely slow.
157 	 */
158 	ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
159 	ts->tv_nsec = ns;
160 
161 	return 0;
162 }
163 
164 #ifdef CONFIG_TIME_NS
do_coarse_timens(const struct vdso_data * vdns,clockid_t clk,struct __kernel_timespec * ts)165 static __always_inline int do_coarse_timens(const struct vdso_data *vdns, clockid_t clk,
166 					    struct __kernel_timespec *ts)
167 {
168 	const struct vdso_data *vd = __arch_get_timens_vdso_data(vdns);
169 	const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
170 	const struct timens_offset *offs = &vdns->offset[clk];
171 	u64 nsec;
172 	s64 sec;
173 	s32 seq;
174 
175 	do {
176 		seq = vdso_read_begin(vd);
177 		sec = vdso_ts->sec;
178 		nsec = vdso_ts->nsec;
179 	} while (unlikely(vdso_read_retry(vd, seq)));
180 
181 	/* Add the namespace offset */
182 	sec += offs->sec;
183 	nsec += offs->nsec;
184 
185 	/*
186 	 * Do this outside the loop: a race inside the loop could result
187 	 * in __iter_div_u64_rem() being extremely slow.
188 	 */
189 	ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
190 	ts->tv_nsec = nsec;
191 	return 0;
192 }
193 #else
do_coarse_timens(const struct vdso_data * vdns,clockid_t clk,struct __kernel_timespec * ts)194 static __always_inline int do_coarse_timens(const struct vdso_data *vdns, clockid_t clk,
195 					    struct __kernel_timespec *ts)
196 {
197 	return -1;
198 }
199 #endif
200 
do_coarse(const struct vdso_data * vd,clockid_t clk,struct __kernel_timespec * ts)201 static __always_inline int do_coarse(const struct vdso_data *vd, clockid_t clk,
202 				     struct __kernel_timespec *ts)
203 {
204 	const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
205 	u32 seq;
206 
207 	do {
208 		/*
209 		 * Open coded to handle VDSO_CLOCK_TIMENS. See comment in
210 		 * do_hres().
211 		 */
212 		while ((seq = READ_ONCE(vd->seq)) & 1) {
213 			if (IS_ENABLED(CONFIG_TIME_NS) &&
214 			    vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
215 				return do_coarse_timens(vd, clk, ts);
216 			cpu_relax();
217 		}
218 		smp_rmb();
219 
220 		ts->tv_sec = vdso_ts->sec;
221 		ts->tv_nsec = vdso_ts->nsec;
222 	} while (unlikely(vdso_read_retry(vd, seq)));
223 
224 	return 0;
225 }
226 
227 static __always_inline int
__cvdso_clock_gettime_common(const struct vdso_data * vd,clockid_t clock,struct __kernel_timespec * ts)228 __cvdso_clock_gettime_common(const struct vdso_data *vd, clockid_t clock,
229 			     struct __kernel_timespec *ts)
230 {
231 	u32 msk;
232 
233 	/* Check for negative values or invalid clocks */
234 	if (unlikely((u32) clock >= MAX_CLOCKS))
235 		return -1;
236 
237 	/*
238 	 * Convert the clockid to a bitmask and use it to check which
239 	 * clocks are handled in the VDSO directly.
240 	 */
241 	msk = 1U << clock;
242 	if (likely(msk & VDSO_HRES))
243 		vd = &vd[CS_HRES_COARSE];
244 	else if (msk & VDSO_COARSE)
245 		return do_coarse(&vd[CS_HRES_COARSE], clock, ts);
246 	else if (msk & VDSO_RAW)
247 		vd = &vd[CS_RAW];
248 	else
249 		return -1;
250 
251 	return do_hres(vd, clock, ts);
252 }
253 
254 static __maybe_unused int
__cvdso_clock_gettime_data(const struct vdso_data * vd,clockid_t clock,struct __kernel_timespec * ts)255 __cvdso_clock_gettime_data(const struct vdso_data *vd, clockid_t clock,
256 			   struct __kernel_timespec *ts)
257 {
258 	int ret = __cvdso_clock_gettime_common(vd, clock, ts);
259 
260 	if (unlikely(ret))
261 		return clock_gettime_fallback(clock, ts);
262 	return 0;
263 }
264 
265 static __maybe_unused int
__cvdso_clock_gettime(clockid_t clock,struct __kernel_timespec * ts)266 __cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
267 {
268 	return __cvdso_clock_gettime_data(__arch_get_vdso_data(), clock, ts);
269 }
270 
271 #ifdef BUILD_VDSO32
272 static __maybe_unused int
__cvdso_clock_gettime32_data(const struct vdso_data * vd,clockid_t clock,struct old_timespec32 * res)273 __cvdso_clock_gettime32_data(const struct vdso_data *vd, clockid_t clock,
274 			     struct old_timespec32 *res)
275 {
276 	struct __kernel_timespec ts;
277 	int ret;
278 
279 	ret = __cvdso_clock_gettime_common(vd, clock, &ts);
280 
281 	if (unlikely(ret))
282 		return clock_gettime32_fallback(clock, res);
283 
284 	/* For ret == 0 */
285 	res->tv_sec = ts.tv_sec;
286 	res->tv_nsec = ts.tv_nsec;
287 
288 	return ret;
289 }
290 
291 static __maybe_unused int
__cvdso_clock_gettime32(clockid_t clock,struct old_timespec32 * res)292 __cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
293 {
294 	return __cvdso_clock_gettime32_data(__arch_get_vdso_data(), clock, res);
295 }
296 #endif /* BUILD_VDSO32 */
297 
298 static __maybe_unused int
__cvdso_gettimeofday_data(const struct vdso_data * vd,struct __kernel_old_timeval * tv,struct timezone * tz)299 __cvdso_gettimeofday_data(const struct vdso_data *vd,
300 			  struct __kernel_old_timeval *tv, struct timezone *tz)
301 {
302 
303 	if (likely(tv != NULL)) {
304 		struct __kernel_timespec ts;
305 
306 		if (do_hres(&vd[CS_HRES_COARSE], CLOCK_REALTIME, &ts))
307 			return gettimeofday_fallback(tv, tz);
308 
309 		tv->tv_sec = ts.tv_sec;
310 		tv->tv_usec = (u32)ts.tv_nsec / NSEC_PER_USEC;
311 	}
312 
313 	if (unlikely(tz != NULL)) {
314 		if (IS_ENABLED(CONFIG_TIME_NS) &&
315 		    vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
316 			vd = __arch_get_timens_vdso_data(vd);
317 
318 		tz->tz_minuteswest = vd[CS_HRES_COARSE].tz_minuteswest;
319 		tz->tz_dsttime = vd[CS_HRES_COARSE].tz_dsttime;
320 	}
321 
322 	return 0;
323 }
324 
325 static __maybe_unused int
__cvdso_gettimeofday(struct __kernel_old_timeval * tv,struct timezone * tz)326 __cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
327 {
328 	return __cvdso_gettimeofday_data(__arch_get_vdso_data(), tv, tz);
329 }
330 
331 #ifdef VDSO_HAS_TIME
332 static __maybe_unused __kernel_old_time_t
__cvdso_time_data(const struct vdso_data * vd,__kernel_old_time_t * time)333 __cvdso_time_data(const struct vdso_data *vd, __kernel_old_time_t *time)
334 {
335 	__kernel_old_time_t t;
336 
337 	if (IS_ENABLED(CONFIG_TIME_NS) &&
338 	    vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
339 		vd = __arch_get_timens_vdso_data(vd);
340 
341 	t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec);
342 
343 	if (time)
344 		*time = t;
345 
346 	return t;
347 }
348 
__cvdso_time(__kernel_old_time_t * time)349 static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time)
350 {
351 	return __cvdso_time_data(__arch_get_vdso_data(), time);
352 }
353 #endif /* VDSO_HAS_TIME */
354 
355 #ifdef VDSO_HAS_CLOCK_GETRES
356 static __maybe_unused
__cvdso_clock_getres_common(const struct vdso_data * vd,clockid_t clock,struct __kernel_timespec * res)357 int __cvdso_clock_getres_common(const struct vdso_data *vd, clockid_t clock,
358 				struct __kernel_timespec *res)
359 {
360 	u32 msk;
361 	u64 ns;
362 
363 	/* Check for negative values or invalid clocks */
364 	if (unlikely((u32) clock >= MAX_CLOCKS))
365 		return -1;
366 
367 	if (IS_ENABLED(CONFIG_TIME_NS) &&
368 	    vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
369 		vd = __arch_get_timens_vdso_data(vd);
370 
371 	/*
372 	 * Convert the clockid to a bitmask and use it to check which
373 	 * clocks are handled in the VDSO directly.
374 	 */
375 	msk = 1U << clock;
376 	if (msk & (VDSO_HRES | VDSO_RAW)) {
377 		/*
378 		 * Preserves the behaviour of posix_get_hrtimer_res().
379 		 */
380 		ns = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res);
381 	} else if (msk & VDSO_COARSE) {
382 		/*
383 		 * Preserves the behaviour of posix_get_coarse_res().
384 		 */
385 		ns = LOW_RES_NSEC;
386 	} else {
387 		return -1;
388 	}
389 
390 	if (likely(res)) {
391 		res->tv_sec = 0;
392 		res->tv_nsec = ns;
393 	}
394 	return 0;
395 }
396 
397 static __maybe_unused
__cvdso_clock_getres_data(const struct vdso_data * vd,clockid_t clock,struct __kernel_timespec * res)398 int __cvdso_clock_getres_data(const struct vdso_data *vd, clockid_t clock,
399 			      struct __kernel_timespec *res)
400 {
401 	int ret = __cvdso_clock_getres_common(vd, clock, res);
402 
403 	if (unlikely(ret))
404 		return clock_getres_fallback(clock, res);
405 	return 0;
406 }
407 
408 static __maybe_unused
__cvdso_clock_getres(clockid_t clock,struct __kernel_timespec * res)409 int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
410 {
411 	return __cvdso_clock_getres_data(__arch_get_vdso_data(), clock, res);
412 }
413 
414 #ifdef BUILD_VDSO32
415 static __maybe_unused int
__cvdso_clock_getres_time32_data(const struct vdso_data * vd,clockid_t clock,struct old_timespec32 * res)416 __cvdso_clock_getres_time32_data(const struct vdso_data *vd, clockid_t clock,
417 				 struct old_timespec32 *res)
418 {
419 	struct __kernel_timespec ts;
420 	int ret;
421 
422 	ret = __cvdso_clock_getres_common(vd, clock, &ts);
423 
424 	if (unlikely(ret))
425 		return clock_getres32_fallback(clock, res);
426 
427 	if (likely(res)) {
428 		res->tv_sec = ts.tv_sec;
429 		res->tv_nsec = ts.tv_nsec;
430 	}
431 	return ret;
432 }
433 
434 static __maybe_unused int
__cvdso_clock_getres_time32(clockid_t clock,struct old_timespec32 * res)435 __cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res)
436 {
437 	return __cvdso_clock_getres_time32_data(__arch_get_vdso_data(),
438 						clock, res);
439 }
440 #endif /* BUILD_VDSO32 */
441 #endif /* VDSO_HAS_CLOCK_GETRES */
442