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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Fast user context implementation of clock_gettime, gettimeofday, and time.
4 *
5 * Copyright 2006 Andi Kleen, SUSE Labs.
6 * Copyright 2019 ARM Limited
7 *
8 * 32 Bit compat layer by Stefani Seibold <stefani@seibold.net>
9 * sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
10 */
11#include <linux/time.h>
12#include <linux/kernel.h>
13#include <linux/types.h>
14
15#include "../../../../lib/vdso/gettimeofday.c"
16
17extern int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz);
18extern __kernel_old_time_t __vdso_time(__kernel_old_time_t *t);
19
20int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
21{
22 return __cvdso_gettimeofday(tv, tz);
23}
24
25int gettimeofday(struct __kernel_old_timeval *, struct timezone *)
26 __attribute__((weak, alias("__vdso_gettimeofday")));
27
28__kernel_old_time_t __vdso_time(__kernel_old_time_t *t)
29{
30 return __cvdso_time(t);
31}
32
33__kernel_old_time_t time(__kernel_old_time_t *t) __attribute__((weak, alias("__vdso_time")));
34
35
36#if defined(CONFIG_X86_64) && !defined(BUILD_VDSO32_64)
37/* both 64-bit and x32 use these */
38extern int __vdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts);
39extern int __vdso_clock_getres(clockid_t clock, struct __kernel_timespec *res);
40
41int __vdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
42{
43 return __cvdso_clock_gettime(clock, ts);
44}
45
46int clock_gettime(clockid_t, struct __kernel_timespec *)
47 __attribute__((weak, alias("__vdso_clock_gettime")));
48
49int __vdso_clock_getres(clockid_t clock,
50 struct __kernel_timespec *res)
51{
52 return __cvdso_clock_getres(clock, res);
53}
54int clock_getres(clockid_t, struct __kernel_timespec *)
55 __attribute__((weak, alias("__vdso_clock_getres")));
56
57#else
58/* i386 only */
59extern int __vdso_clock_gettime(clockid_t clock, struct old_timespec32 *ts);
60extern int __vdso_clock_getres(clockid_t clock, struct old_timespec32 *res);
61
62int __vdso_clock_gettime(clockid_t clock, struct old_timespec32 *ts)
63{
64 return __cvdso_clock_gettime32(clock, ts);
65}
66
67int clock_gettime(clockid_t, struct old_timespec32 *)
68 __attribute__((weak, alias("__vdso_clock_gettime")));
69
70int __vdso_clock_gettime64(clockid_t clock, struct __kernel_timespec *ts)
71{
72 return __cvdso_clock_gettime(clock, ts);
73}
74
75int clock_gettime64(clockid_t, struct __kernel_timespec *)
76 __attribute__((weak, alias("__vdso_clock_gettime64")));
77
78int __vdso_clock_getres(clockid_t clock, struct old_timespec32 *res)
79{
80 return __cvdso_clock_getres_time32(clock, res);
81}
82
83int clock_getres(clockid_t, struct old_timespec32 *)
84 __attribute__((weak, alias("__vdso_clock_getres")));
85#endif
1/*
2 * Copyright 2006 Andi Kleen, SUSE Labs.
3 * Subject to the GNU Public License, v.2
4 *
5 * Fast user context implementation of clock_gettime, gettimeofday, and time.
6 *
7 * 32 Bit compat layer by Stefani Seibold <stefani@seibold.net>
8 * sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
9 *
10 * The code should have no internal unresolved relocations.
11 * Check with readelf after changing.
12 */
13
14#include <uapi/linux/time.h>
15#include <asm/vgtod.h>
16#include <asm/hpet.h>
17#include <asm/vvar.h>
18#include <asm/unistd.h>
19#include <asm/msr.h>
20#include <asm/pvclock.h>
21#include <linux/math64.h>
22#include <linux/time.h>
23#include <linux/kernel.h>
24
25#define gtod (&VVAR(vsyscall_gtod_data))
26
27extern int __vdso_clock_gettime(clockid_t clock, struct timespec *ts);
28extern int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz);
29extern time_t __vdso_time(time_t *t);
30
31#ifdef CONFIG_HPET_TIMER
32extern u8 hpet_page
33 __attribute__((visibility("hidden")));
34
35static notrace cycle_t vread_hpet(void)
36{
37 return *(const volatile u32 *)(&hpet_page + HPET_COUNTER);
38}
39#endif
40
41#ifdef CONFIG_PARAVIRT_CLOCK
42extern u8 pvclock_page
43 __attribute__((visibility("hidden")));
44#endif
45
46#ifndef BUILD_VDSO32
47
48notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
49{
50 long ret;
51 asm("syscall" : "=a" (ret) :
52 "0" (__NR_clock_gettime), "D" (clock), "S" (ts) : "memory");
53 return ret;
54}
55
56notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
57{
58 long ret;
59
60 asm("syscall" : "=a" (ret) :
61 "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
62 return ret;
63}
64
65
66#else
67
68notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
69{
70 long ret;
71
72 asm(
73 "mov %%ebx, %%edx \n"
74 "mov %2, %%ebx \n"
75 "call __kernel_vsyscall \n"
76 "mov %%edx, %%ebx \n"
77 : "=a" (ret)
78 : "0" (__NR_clock_gettime), "g" (clock), "c" (ts)
79 : "memory", "edx");
80 return ret;
81}
82
83notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
84{
85 long ret;
86
87 asm(
88 "mov %%ebx, %%edx \n"
89 "mov %2, %%ebx \n"
90 "call __kernel_vsyscall \n"
91 "mov %%edx, %%ebx \n"
92 : "=a" (ret)
93 : "0" (__NR_gettimeofday), "g" (tv), "c" (tz)
94 : "memory", "edx");
95 return ret;
96}
97
98#endif
99
100#ifdef CONFIG_PARAVIRT_CLOCK
101static notrace const struct pvclock_vsyscall_time_info *get_pvti0(void)
102{
103 return (const struct pvclock_vsyscall_time_info *)&pvclock_page;
104}
105
106static notrace cycle_t vread_pvclock(int *mode)
107{
108 const struct pvclock_vcpu_time_info *pvti = &get_pvti0()->pvti;
109 cycle_t ret;
110 u64 tsc, pvti_tsc;
111 u64 last, delta, pvti_system_time;
112 u32 version, pvti_tsc_to_system_mul, pvti_tsc_shift;
113
114 /*
115 * Note: The kernel and hypervisor must guarantee that cpu ID
116 * number maps 1:1 to per-CPU pvclock time info.
117 *
118 * Because the hypervisor is entirely unaware of guest userspace
119 * preemption, it cannot guarantee that per-CPU pvclock time
120 * info is updated if the underlying CPU changes or that that
121 * version is increased whenever underlying CPU changes.
122 *
123 * On KVM, we are guaranteed that pvti updates for any vCPU are
124 * atomic as seen by *all* vCPUs. This is an even stronger
125 * guarantee than we get with a normal seqlock.
126 *
127 * On Xen, we don't appear to have that guarantee, but Xen still
128 * supplies a valid seqlock using the version field.
129 *
130 * We only do pvclock vdso timing at all if
131 * PVCLOCK_TSC_STABLE_BIT is set, and we interpret that bit to
132 * mean that all vCPUs have matching pvti and that the TSC is
133 * synced, so we can just look at vCPU 0's pvti.
134 */
135
136 do {
137 version = pvti->version;
138
139 smp_rmb();
140
141 if (unlikely(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT))) {
142 *mode = VCLOCK_NONE;
143 return 0;
144 }
145
146 tsc = rdtsc_ordered();
147 pvti_tsc_to_system_mul = pvti->tsc_to_system_mul;
148 pvti_tsc_shift = pvti->tsc_shift;
149 pvti_system_time = pvti->system_time;
150 pvti_tsc = pvti->tsc_timestamp;
151
152 /* Make sure that the version double-check is last. */
153 smp_rmb();
154 } while (unlikely((version & 1) || version != pvti->version));
155
156 delta = tsc - pvti_tsc;
157 ret = pvti_system_time +
158 pvclock_scale_delta(delta, pvti_tsc_to_system_mul,
159 pvti_tsc_shift);
160
161 /* refer to vread_tsc() comment for rationale */
162 last = gtod->cycle_last;
163
164 if (likely(ret >= last))
165 return ret;
166
167 return last;
168}
169#endif
170
171notrace static cycle_t vread_tsc(void)
172{
173 cycle_t ret = (cycle_t)rdtsc_ordered();
174 u64 last = gtod->cycle_last;
175
176 if (likely(ret >= last))
177 return ret;
178
179 /*
180 * GCC likes to generate cmov here, but this branch is extremely
181 * predictable (it's just a function of time and the likely is
182 * very likely) and there's a data dependence, so force GCC
183 * to generate a branch instead. I don't barrier() because
184 * we don't actually need a barrier, and if this function
185 * ever gets inlined it will generate worse code.
186 */
187 asm volatile ("");
188 return last;
189}
190
191notrace static inline u64 vgetsns(int *mode)
192{
193 u64 v;
194 cycles_t cycles;
195
196 if (gtod->vclock_mode == VCLOCK_TSC)
197 cycles = vread_tsc();
198#ifdef CONFIG_HPET_TIMER
199 else if (gtod->vclock_mode == VCLOCK_HPET)
200 cycles = vread_hpet();
201#endif
202#ifdef CONFIG_PARAVIRT_CLOCK
203 else if (gtod->vclock_mode == VCLOCK_PVCLOCK)
204 cycles = vread_pvclock(mode);
205#endif
206 else
207 return 0;
208 v = (cycles - gtod->cycle_last) & gtod->mask;
209 return v * gtod->mult;
210}
211
212/* Code size doesn't matter (vdso is 4k anyway) and this is faster. */
213notrace static int __always_inline do_realtime(struct timespec *ts)
214{
215 unsigned long seq;
216 u64 ns;
217 int mode;
218
219 do {
220 seq = gtod_read_begin(gtod);
221 mode = gtod->vclock_mode;
222 ts->tv_sec = gtod->wall_time_sec;
223 ns = gtod->wall_time_snsec;
224 ns += vgetsns(&mode);
225 ns >>= gtod->shift;
226 } while (unlikely(gtod_read_retry(gtod, seq)));
227
228 ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
229 ts->tv_nsec = ns;
230
231 return mode;
232}
233
234notrace static int __always_inline do_monotonic(struct timespec *ts)
235{
236 unsigned long seq;
237 u64 ns;
238 int mode;
239
240 do {
241 seq = gtod_read_begin(gtod);
242 mode = gtod->vclock_mode;
243 ts->tv_sec = gtod->monotonic_time_sec;
244 ns = gtod->monotonic_time_snsec;
245 ns += vgetsns(&mode);
246 ns >>= gtod->shift;
247 } while (unlikely(gtod_read_retry(gtod, seq)));
248
249 ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
250 ts->tv_nsec = ns;
251
252 return mode;
253}
254
255notrace static void do_realtime_coarse(struct timespec *ts)
256{
257 unsigned long seq;
258 do {
259 seq = gtod_read_begin(gtod);
260 ts->tv_sec = gtod->wall_time_coarse_sec;
261 ts->tv_nsec = gtod->wall_time_coarse_nsec;
262 } while (unlikely(gtod_read_retry(gtod, seq)));
263}
264
265notrace static void do_monotonic_coarse(struct timespec *ts)
266{
267 unsigned long seq;
268 do {
269 seq = gtod_read_begin(gtod);
270 ts->tv_sec = gtod->monotonic_time_coarse_sec;
271 ts->tv_nsec = gtod->monotonic_time_coarse_nsec;
272 } while (unlikely(gtod_read_retry(gtod, seq)));
273}
274
275notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
276{
277 switch (clock) {
278 case CLOCK_REALTIME:
279 if (do_realtime(ts) == VCLOCK_NONE)
280 goto fallback;
281 break;
282 case CLOCK_MONOTONIC:
283 if (do_monotonic(ts) == VCLOCK_NONE)
284 goto fallback;
285 break;
286 case CLOCK_REALTIME_COARSE:
287 do_realtime_coarse(ts);
288 break;
289 case CLOCK_MONOTONIC_COARSE:
290 do_monotonic_coarse(ts);
291 break;
292 default:
293 goto fallback;
294 }
295
296 return 0;
297fallback:
298 return vdso_fallback_gettime(clock, ts);
299}
300int clock_gettime(clockid_t, struct timespec *)
301 __attribute__((weak, alias("__vdso_clock_gettime")));
302
303notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
304{
305 if (likely(tv != NULL)) {
306 if (unlikely(do_realtime((struct timespec *)tv) == VCLOCK_NONE))
307 return vdso_fallback_gtod(tv, tz);
308 tv->tv_usec /= 1000;
309 }
310 if (unlikely(tz != NULL)) {
311 tz->tz_minuteswest = gtod->tz_minuteswest;
312 tz->tz_dsttime = gtod->tz_dsttime;
313 }
314
315 return 0;
316}
317int gettimeofday(struct timeval *, struct timezone *)
318 __attribute__((weak, alias("__vdso_gettimeofday")));
319
320/*
321 * This will break when the xtime seconds get inaccurate, but that is
322 * unlikely
323 */
324notrace time_t __vdso_time(time_t *t)
325{
326 /* This is atomic on x86 so we don't need any locks. */
327 time_t result = ACCESS_ONCE(gtod->wall_time_sec);
328
329 if (t)
330 *t = result;
331 return result;
332}
333int time(time_t *t)
334 __attribute__((weak, alias("__vdso_time")));