1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Generic userspace implementations of gettimeofday() and similar. 4 */ 5 #include <linux/compiler.h> 6 #include <linux/math64.h> 7 #include <linux/time.h> 8 #include <linux/kernel.h> 9 #include <linux/hrtimer_defs.h> 10 #include <vdso/datapage.h> 11 #include <vdso/helpers.h> 12 13 /* 14 * The generic vDSO implementation requires that gettimeofday.h 15 * provides: 16 * - __arch_get_vdso_data(): to get the vdso datapage. 17 * - __arch_get_hw_counter(): to get the hw counter based on the 18 * clock_mode. 19 * - gettimeofday_fallback(): fallback for gettimeofday. 20 * - clock_gettime_fallback(): fallback for clock_gettime. 21 * - clock_getres_fallback(): fallback for clock_getres. 22 */ 23 #ifdef ENABLE_COMPAT_VDSO 24 #include <asm/vdso/compat_gettimeofday.h> 25 #else 26 #include <asm/vdso/gettimeofday.h> 27 #endif /* ENABLE_COMPAT_VDSO */ 28 29 #ifndef vdso_calc_delta 30 /* 31 * Default implementation which works for all sane clocksources. That 32 * obviously excludes x86/TSC. 33 */ 34 static __always_inline 35 u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult) 36 { 37 return ((cycles - last) & mask) * mult; 38 } 39 #endif 40 41 static int do_hres(const struct vdso_data *vd, clockid_t clk, 42 struct __kernel_timespec *ts) 43 { 44 const struct vdso_timestamp *vdso_ts = &vd->basetime[clk]; 45 u64 cycles, last, sec, ns; 46 u32 seq; 47 48 do { 49 seq = vdso_read_begin(vd); 50 cycles = __arch_get_hw_counter(vd->clock_mode); 51 ns = vdso_ts->nsec; 52 last = vd->cycle_last; 53 if (unlikely((s64)cycles < 0)) 54 return clock_gettime_fallback(clk, ts); 55 56 ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult); 57 ns >>= vd->shift; 58 sec = vdso_ts->sec; 59 } while (unlikely(vdso_read_retry(vd, seq))); 60 61 /* 62 * Do this outside the loop: a race inside the loop could result 63 * in __iter_div_u64_rem() being extremely slow. 64 */ 65 ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns); 66 ts->tv_nsec = ns; 67 68 return 0; 69 } 70 71 static void do_coarse(const struct vdso_data *vd, clockid_t clk, 72 struct __kernel_timespec *ts) 73 { 74 const struct vdso_timestamp *vdso_ts = &vd->basetime[clk]; 75 u32 seq; 76 77 do { 78 seq = vdso_read_begin(vd); 79 ts->tv_sec = vdso_ts->sec; 80 ts->tv_nsec = vdso_ts->nsec; 81 } while (unlikely(vdso_read_retry(vd, seq))); 82 } 83 84 static __maybe_unused int 85 __cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts) 86 { 87 const struct vdso_data *vd = __arch_get_vdso_data(); 88 u32 msk; 89 90 /* Check for negative values or invalid clocks */ 91 if (unlikely((u32) clock >= MAX_CLOCKS)) 92 goto fallback; 93 94 /* 95 * Convert the clockid to a bitmask and use it to check which 96 * clocks are handled in the VDSO directly. 97 */ 98 msk = 1U << clock; 99 if (likely(msk & VDSO_HRES)) { 100 return do_hres(&vd[CS_HRES_COARSE], clock, ts); 101 } else if (msk & VDSO_COARSE) { 102 do_coarse(&vd[CS_HRES_COARSE], clock, ts); 103 return 0; 104 } else if (msk & VDSO_RAW) { 105 return do_hres(&vd[CS_RAW], clock, ts); 106 } 107 108 fallback: 109 return clock_gettime_fallback(clock, ts); 110 } 111 112 static __maybe_unused int 113 __cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res) 114 { 115 struct __kernel_timespec ts; 116 int ret; 117 118 if (res == NULL) 119 goto fallback; 120 121 ret = __cvdso_clock_gettime(clock, &ts); 122 123 if (ret == 0) { 124 res->tv_sec = ts.tv_sec; 125 res->tv_nsec = ts.tv_nsec; 126 } 127 128 return ret; 129 130 fallback: 131 return clock_gettime_fallback(clock, (struct __kernel_timespec *)res); 132 } 133 134 static __maybe_unused int 135 __cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz) 136 { 137 const struct vdso_data *vd = __arch_get_vdso_data(); 138 139 if (likely(tv != NULL)) { 140 struct __kernel_timespec ts; 141 142 if (do_hres(&vd[CS_HRES_COARSE], CLOCK_REALTIME, &ts)) 143 return gettimeofday_fallback(tv, tz); 144 145 tv->tv_sec = ts.tv_sec; 146 tv->tv_usec = (u32)ts.tv_nsec / NSEC_PER_USEC; 147 } 148 149 if (unlikely(tz != NULL)) { 150 tz->tz_minuteswest = vd[CS_HRES_COARSE].tz_minuteswest; 151 tz->tz_dsttime = vd[CS_HRES_COARSE].tz_dsttime; 152 } 153 154 return 0; 155 } 156 157 #ifdef VDSO_HAS_TIME 158 static __maybe_unused time_t __cvdso_time(time_t *time) 159 { 160 const struct vdso_data *vd = __arch_get_vdso_data(); 161 time_t t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec); 162 163 if (time) 164 *time = t; 165 166 return t; 167 } 168 #endif /* VDSO_HAS_TIME */ 169 170 #ifdef VDSO_HAS_CLOCK_GETRES 171 static __maybe_unused 172 int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res) 173 { 174 const struct vdso_data *vd = __arch_get_vdso_data(); 175 u64 ns; 176 u32 msk; 177 u64 hrtimer_res = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res); 178 179 /* Check for negative values or invalid clocks */ 180 if (unlikely((u32) clock >= MAX_CLOCKS)) 181 goto fallback; 182 183 /* 184 * Convert the clockid to a bitmask and use it to check which 185 * clocks are handled in the VDSO directly. 186 */ 187 msk = 1U << clock; 188 if (msk & VDSO_HRES) { 189 /* 190 * Preserves the behaviour of posix_get_hrtimer_res(). 191 */ 192 ns = hrtimer_res; 193 } else if (msk & VDSO_COARSE) { 194 /* 195 * Preserves the behaviour of posix_get_coarse_res(). 196 */ 197 ns = LOW_RES_NSEC; 198 } else if (msk & VDSO_RAW) { 199 /* 200 * Preserves the behaviour of posix_get_hrtimer_res(). 201 */ 202 ns = hrtimer_res; 203 } else { 204 goto fallback; 205 } 206 207 if (res) { 208 res->tv_sec = 0; 209 res->tv_nsec = ns; 210 } 211 212 return 0; 213 214 fallback: 215 return clock_getres_fallback(clock, res); 216 } 217 218 static __maybe_unused int 219 __cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res) 220 { 221 struct __kernel_timespec ts; 222 int ret; 223 224 if (res == NULL) 225 goto fallback; 226 227 ret = __cvdso_clock_getres(clock, &ts); 228 229 if (ret == 0) { 230 res->tv_sec = ts.tv_sec; 231 res->tv_nsec = ts.tv_nsec; 232 } 233 234 return ret; 235 236 fallback: 237 return clock_getres_fallback(clock, (struct __kernel_timespec *)res); 238 } 239 #endif /* VDSO_HAS_CLOCK_GETRES */ 240