vsyscall.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright 2019 ARM Ltd.
  4 *
  5 * Generic implementation of update_vsyscall and update_vsyscall_tz.
  6 *
  7 * Based on the x86 specific implementation.
  8 */
  9
 10#include <linux/hrtimer.h>
 11#include <linux/timekeeper_internal.h>
 12#include <vdso/datapage.h>
 13#include <vdso/helpers.h>
 14#include <vdso/vsyscall.h>
 15
 16#include "timekeeping_internal.h"
 17
 18static inline void fill_clock_configuration(struct vdso_clock *vc, const struct tk_read_base *base)
 19{
 20	vc->cycle_last	= base->cycle_last;
 21#ifdef CONFIG_GENERIC_VDSO_OVERFLOW_PROTECT
 22	vc->max_cycles	= base->clock->max_cycles;
 23#endif
 24	vc->mask	= base->mask;
 25	vc->mult	= base->mult;
 26	vc->shift	= base->shift;
 27}
 28
 29static inline void update_vdso_time_data(struct vdso_time_data *vdata, struct timekeeper *tk)
 30{
 31	struct vdso_clock *vc = vdata->clock_data;
 32	struct vdso_timestamp *vdso_ts;
 33	u64 nsec, sec;
 34
 35	fill_clock_configuration(&vc[CS_HRES_COARSE],	&tk->tkr_mono);
 36	fill_clock_configuration(&vc[CS_RAW],		&tk->tkr_raw);
 37
 38	/* CLOCK_MONOTONIC */
 39	vdso_ts		= &vc[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC];
 40	vdso_ts->sec	= tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
 41
 42	nsec = tk->tkr_mono.xtime_nsec;
 43	nsec += ((u64)tk->wall_to_monotonic.tv_nsec << tk->tkr_mono.shift);
 44	while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
 45		nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
 46		vdso_ts->sec++;
 47	}
 48	vdso_ts->nsec	= nsec;
 49
 50	/* Copy MONOTONIC time for BOOTTIME */
 51	sec	= vdso_ts->sec;
 52	/* Add the boot offset */
 53	sec	+= tk->monotonic_to_boot.tv_sec;
 54	nsec	+= (u64)tk->monotonic_to_boot.tv_nsec << tk->tkr_mono.shift;
 55
 56	/* CLOCK_BOOTTIME */
 57	vdso_ts		= &vc[CS_HRES_COARSE].basetime[CLOCK_BOOTTIME];
 58	vdso_ts->sec	= sec;
 59
 60	while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
 61		nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
 62		vdso_ts->sec++;
 63	}
 64	vdso_ts->nsec	= nsec;
 65
 66	/* CLOCK_MONOTONIC_RAW */
 67	vdso_ts		= &vc[CS_RAW].basetime[CLOCK_MONOTONIC_RAW];
 68	vdso_ts->sec	= tk->raw_sec;
 69	vdso_ts->nsec	= tk->tkr_raw.xtime_nsec;
 70
 71	/* CLOCK_TAI */
 72	vdso_ts		= &vc[CS_HRES_COARSE].basetime[CLOCK_TAI];
 73	vdso_ts->sec	= tk->xtime_sec + (s64)tk->tai_offset;
 74	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec;
 75}
 76
 77void update_vsyscall(struct timekeeper *tk)
 78{
 79	struct vdso_time_data *vdata = vdso_k_time_data;
 80	struct vdso_clock *vc = vdata->clock_data;
 81	struct vdso_timestamp *vdso_ts;
 82	s32 clock_mode;
 83	u64 nsec;
 84
 85	/* copy vsyscall data */
 86	vdso_write_begin(vdata);
 87
 88	clock_mode = tk->tkr_mono.clock->vdso_clock_mode;
 89	vc[CS_HRES_COARSE].clock_mode	= clock_mode;
 90	vc[CS_RAW].clock_mode		= clock_mode;
 91
 92	/* CLOCK_REALTIME also required for time() */
 93	vdso_ts		= &vc[CS_HRES_COARSE].basetime[CLOCK_REALTIME];
 94	vdso_ts->sec	= tk->xtime_sec;
 95	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec;
 96
 97	/* CLOCK_REALTIME_COARSE */
 98	vdso_ts		= &vc[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE];
 99	vdso_ts->sec	= tk->xtime_sec;
100	vdso_ts->nsec	= tk->coarse_nsec;
101
102	/* CLOCK_MONOTONIC_COARSE */
103	vdso_ts		= &vc[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC_COARSE];
104	vdso_ts->sec	= tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
105	nsec		= tk->coarse_nsec;
106	nsec		= nsec + tk->wall_to_monotonic.tv_nsec;
107	vdso_ts->sec	+= __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec);
108
109	/*
110	 * Read without the seqlock held by clock_getres().
111	 */
112	WRITE_ONCE(vdata->hrtimer_res, hrtimer_resolution);
113
114	/*
115	 * If the current clocksource is not VDSO capable, then spare the
116	 * update of the high resolution parts.
117	 */
118	if (clock_mode != VDSO_CLOCKMODE_NONE)
119		update_vdso_time_data(vdata, tk);
120
121	__arch_update_vdso_clock(&vc[CS_HRES_COARSE]);
122	__arch_update_vdso_clock(&vc[CS_RAW]);
123
124	vdso_write_end(vdata);
125
126	__arch_sync_vdso_time_data(vdata);
127}
128
129void update_vsyscall_tz(void)
130{
131	struct vdso_time_data *vdata = vdso_k_time_data;
132
133	vdata->tz_minuteswest = sys_tz.tz_minuteswest;
134	vdata->tz_dsttime = sys_tz.tz_dsttime;
135
136	__arch_sync_vdso_time_data(vdata);
137}
138
139#ifdef CONFIG_POSIX_AUX_CLOCKS
140void vdso_time_update_aux(struct timekeeper *tk)
141{
142	struct vdso_time_data *vdata = vdso_k_time_data;
143	struct vdso_timestamp *vdso_ts;
144	struct vdso_clock *vc;
145	s32 clock_mode;
146	u64 nsec;
147
148	vc = &vdata->aux_clock_data[tk->id - TIMEKEEPER_AUX_FIRST];
149	vdso_ts = &vc->basetime[VDSO_BASE_AUX];
150	clock_mode = tk->tkr_mono.clock->vdso_clock_mode;
151	if (!tk->clock_valid)
152		clock_mode = VDSO_CLOCKMODE_NONE;
153
154	/* copy vsyscall data */
155	vdso_write_begin_clock(vc);
156
157	vc->clock_mode = clock_mode;
158
159	if (clock_mode != VDSO_CLOCKMODE_NONE) {
160		fill_clock_configuration(vc, &tk->tkr_mono);
161
162		vdso_ts->sec = tk->xtime_sec + tk->monotonic_to_aux.tv_sec;
163
164		nsec = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
165		nsec += tk->monotonic_to_aux.tv_nsec;
166		vdso_ts->sec += __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
167		nsec = nsec << tk->tkr_mono.shift;
168		vdso_ts->nsec = nsec;
169	}
170
171	__arch_update_vdso_clock(vc);
172
173	vdso_write_end_clock(vc);
174
175	__arch_sync_vdso_time_data(vdata);
176}
177#endif
178
179/**
180 * vdso_update_begin - Start of a VDSO update section
181 *
182 * Allows architecture code to safely update the architecture specific VDSO
183 * data. Disables interrupts, acquires timekeeper lock to serialize against
184 * concurrent updates from timekeeping and invalidates the VDSO data
185 * sequence counter to prevent concurrent readers from accessing
186 * inconsistent data.
187 *
188 * Returns: Saved interrupt flags which need to be handed in to
189 * vdso_update_end().
190 */
191unsigned long vdso_update_begin(void)
192{
193	struct vdso_time_data *vdata = vdso_k_time_data;
194	unsigned long flags = timekeeper_lock_irqsave();
195
196	vdso_write_begin(vdata);
197	return flags;
198}
199
200/**
201 * vdso_update_end - End of a VDSO update section
202 * @flags:	Interrupt flags as returned from vdso_update_begin()
203 *
204 * Pairs with vdso_update_begin(). Marks vdso data consistent, invokes data
205 * synchronization if the architecture requires it, drops timekeeper lock
206 * and restores interrupt flags.
207 */
208void vdso_update_end(unsigned long flags)
209{
210	struct vdso_time_data *vdata = vdso_k_time_data;
211
212	vdso_write_end(vdata);
213	__arch_sync_vdso_time_data(vdata);
214	timekeeper_unlock_irqrestore(flags);
215}