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Linux/arch/arm/vdso/vgettimeofday.c

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  1 /*
  2  * Copyright 2015 Mentor Graphics Corporation.
  3  *
  4  * This program is free software; you can redistribute it and/or
  5  * modify it under the terms of the GNU General Public License
  6  * as published by the Free Software Foundation; version 2 of the
  7  * License.
  8  *
  9  * This program is distributed in the hope that it will be useful, but
 10  * WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 12  * General Public License for more details.
 13  *
 14  * You should have received a copy of the GNU General Public License
 15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 16  */
 17 
 18 #include <linux/compiler.h>
 19 #include <linux/hrtimer.h>
 20 #include <linux/time.h>
 21 #include <asm/arch_timer.h>
 22 #include <asm/barrier.h>
 23 #include <asm/bug.h>
 24 #include <asm/page.h>
 25 #include <asm/unistd.h>
 26 #include <asm/vdso_datapage.h>
 27 
 28 #ifndef CONFIG_AEABI
 29 #error This code depends on AEABI system call conventions
 30 #endif
 31 
 32 extern struct vdso_data *__get_datapage(void);
 33 
 34 static notrace u32 __vdso_read_begin(const struct vdso_data *vdata)
 35 {
 36         u32 seq;
 37 repeat:
 38         seq = ACCESS_ONCE(vdata->seq_count);
 39         if (seq & 1) {
 40                 cpu_relax();
 41                 goto repeat;
 42         }
 43         return seq;
 44 }
 45 
 46 static notrace u32 vdso_read_begin(const struct vdso_data *vdata)
 47 {
 48         u32 seq;
 49 
 50         seq = __vdso_read_begin(vdata);
 51 
 52         smp_rmb(); /* Pairs with smp_wmb in vdso_write_end */
 53         return seq;
 54 }
 55 
 56 static notrace int vdso_read_retry(const struct vdso_data *vdata, u32 start)
 57 {
 58         smp_rmb(); /* Pairs with smp_wmb in vdso_write_begin */
 59         return vdata->seq_count != start;
 60 }
 61 
 62 static notrace long clock_gettime_fallback(clockid_t _clkid,
 63                                            struct timespec *_ts)
 64 {
 65         register struct timespec *ts asm("r1") = _ts;
 66         register clockid_t clkid asm("r0") = _clkid;
 67         register long ret asm ("r0");
 68         register long nr asm("r7") = __NR_clock_gettime;
 69 
 70         asm volatile(
 71         "       swi #0\n"
 72         : "=r" (ret)
 73         : "r" (clkid), "r" (ts), "r" (nr)
 74         : "memory");
 75 
 76         return ret;
 77 }
 78 
 79 static notrace int do_realtime_coarse(struct timespec *ts,
 80                                       struct vdso_data *vdata)
 81 {
 82         u32 seq;
 83 
 84         do {
 85                 seq = vdso_read_begin(vdata);
 86 
 87                 ts->tv_sec = vdata->xtime_coarse_sec;
 88                 ts->tv_nsec = vdata->xtime_coarse_nsec;
 89 
 90         } while (vdso_read_retry(vdata, seq));
 91 
 92         return 0;
 93 }
 94 
 95 static notrace int do_monotonic_coarse(struct timespec *ts,
 96                                        struct vdso_data *vdata)
 97 {
 98         struct timespec tomono;
 99         u32 seq;
100 
101         do {
102                 seq = vdso_read_begin(vdata);
103 
104                 ts->tv_sec = vdata->xtime_coarse_sec;
105                 ts->tv_nsec = vdata->xtime_coarse_nsec;
106 
107                 tomono.tv_sec = vdata->wtm_clock_sec;
108                 tomono.tv_nsec = vdata->wtm_clock_nsec;
109 
110         } while (vdso_read_retry(vdata, seq));
111 
112         ts->tv_sec += tomono.tv_sec;
113         timespec_add_ns(ts, tomono.tv_nsec);
114 
115         return 0;
116 }
117 
118 #ifdef CONFIG_ARM_ARCH_TIMER
119 
120 static notrace u64 get_ns(struct vdso_data *vdata)
121 {
122         u64 cycle_delta;
123         u64 cycle_now;
124         u64 nsec;
125 
126         cycle_now = arch_counter_get_cntvct();
127 
128         cycle_delta = (cycle_now - vdata->cs_cycle_last) & vdata->cs_mask;
129 
130         nsec = (cycle_delta * vdata->cs_mult) + vdata->xtime_clock_snsec;
131         nsec >>= vdata->cs_shift;
132 
133         return nsec;
134 }
135 
136 static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
137 {
138         u64 nsecs;
139         u32 seq;
140 
141         do {
142                 seq = vdso_read_begin(vdata);
143 
144                 if (!vdata->tk_is_cntvct)
145                         return -1;
146 
147                 ts->tv_sec = vdata->xtime_clock_sec;
148                 nsecs = get_ns(vdata);
149 
150         } while (vdso_read_retry(vdata, seq));
151 
152         ts->tv_nsec = 0;
153         timespec_add_ns(ts, nsecs);
154 
155         return 0;
156 }
157 
158 static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
159 {
160         struct timespec tomono;
161         u64 nsecs;
162         u32 seq;
163 
164         do {
165                 seq = vdso_read_begin(vdata);
166 
167                 if (!vdata->tk_is_cntvct)
168                         return -1;
169 
170                 ts->tv_sec = vdata->xtime_clock_sec;
171                 nsecs = get_ns(vdata);
172 
173                 tomono.tv_sec = vdata->wtm_clock_sec;
174                 tomono.tv_nsec = vdata->wtm_clock_nsec;
175 
176         } while (vdso_read_retry(vdata, seq));
177 
178         ts->tv_sec += tomono.tv_sec;
179         ts->tv_nsec = 0;
180         timespec_add_ns(ts, nsecs + tomono.tv_nsec);
181 
182         return 0;
183 }
184 
185 #else /* CONFIG_ARM_ARCH_TIMER */
186 
187 static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
188 {
189         return -1;
190 }
191 
192 static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
193 {
194         return -1;
195 }
196 
197 #endif /* CONFIG_ARM_ARCH_TIMER */
198 
199 notrace int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
200 {
201         struct vdso_data *vdata;
202         int ret = -1;
203 
204         vdata = __get_datapage();
205 
206         switch (clkid) {
207         case CLOCK_REALTIME_COARSE:
208                 ret = do_realtime_coarse(ts, vdata);
209                 break;
210         case CLOCK_MONOTONIC_COARSE:
211                 ret = do_monotonic_coarse(ts, vdata);
212                 break;
213         case CLOCK_REALTIME:
214                 ret = do_realtime(ts, vdata);
215                 break;
216         case CLOCK_MONOTONIC:
217                 ret = do_monotonic(ts, vdata);
218                 break;
219         default:
220                 break;
221         }
222 
223         if (ret)
224                 ret = clock_gettime_fallback(clkid, ts);
225 
226         return ret;
227 }
228 
229 static notrace long gettimeofday_fallback(struct timeval *_tv,
230                                           struct timezone *_tz)
231 {
232         register struct timezone *tz asm("r1") = _tz;
233         register struct timeval *tv asm("r0") = _tv;
234         register long ret asm ("r0");
235         register long nr asm("r7") = __NR_gettimeofday;
236 
237         asm volatile(
238         "       swi #0\n"
239         : "=r" (ret)
240         : "r" (tv), "r" (tz), "r" (nr)
241         : "memory");
242 
243         return ret;
244 }
245 
246 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
247 {
248         struct timespec ts;
249         struct vdso_data *vdata;
250         int ret;
251 
252         vdata = __get_datapage();
253 
254         ret = do_realtime(&ts, vdata);
255         if (ret)
256                 return gettimeofday_fallback(tv, tz);
257 
258         if (tv) {
259                 tv->tv_sec = ts.tv_sec;
260                 tv->tv_usec = ts.tv_nsec / 1000;
261         }
262         if (tz) {
263                 tz->tz_minuteswest = vdata->tz_minuteswest;
264                 tz->tz_dsttime = vdata->tz_dsttime;
265         }
266 
267         return ret;
268 }
269 
270 /* Avoid unresolved references emitted by GCC */
271 
272 void __aeabi_unwind_cpp_pr0(void)
273 {
274 }
275 
276 void __aeabi_unwind_cpp_pr1(void)
277 {
278 }
279 
280 void __aeabi_unwind_cpp_pr2(void)
281 {
282 }
283 

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