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 -1; 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_common(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 return -1; 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 return -1; 108 } 109 110 static __maybe_unused int 111 __cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts) 112 { 113 int ret = __cvdso_clock_gettime_common(clock, ts); 114 115 if (unlikely(ret)) 116 return clock_gettime_fallback(clock, ts); 117 return 0; 118 } 119 120 #ifdef BUILD_VDSO32 121 static __maybe_unused int 122 __cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res) 123 { 124 struct __kernel_timespec ts; 125 int ret; 126 127 ret = __cvdso_clock_gettime_common(clock, &ts); 128 129 if (unlikely(ret)) 130 return clock_gettime32_fallback(clock, res); 131 132 /* For ret == 0 */ 133 res->tv_sec = ts.tv_sec; 134 res->tv_nsec = ts.tv_nsec; 135 136 return ret; 137 } 138 #endif /* BUILD_VDSO32 */ 139 140 static __maybe_unused int 141 __cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz) 142 { 143 const struct vdso_data *vd = __arch_get_vdso_data(); 144 145 if (likely(tv != NULL)) { 146 struct __kernel_timespec ts; 147 148 if (do_hres(&vd[CS_HRES_COARSE], CLOCK_REALTIME, &ts)) 149 return gettimeofday_fallback(tv, tz); 150 151 tv->tv_sec = ts.tv_sec; 152 tv->tv_usec = (u32)ts.tv_nsec / NSEC_PER_USEC; 153 } 154 155 if (unlikely(tz != NULL)) { 156 tz->tz_minuteswest = vd[CS_HRES_COARSE].tz_minuteswest; 157 tz->tz_dsttime = vd[CS_HRES_COARSE].tz_dsttime; 158 } 159 160 return 0; 161 } 162 163 #ifdef VDSO_HAS_TIME 164 static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time) 165 { 166 const struct vdso_data *vd = __arch_get_vdso_data(); 167 __kernel_old_time_t t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec); 168 169 if (time) 170 *time = t; 171 172 return t; 173 } 174 #endif /* VDSO_HAS_TIME */ 175 176 #ifdef VDSO_HAS_CLOCK_GETRES 177 static __maybe_unused 178 int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res) 179 { 180 const struct vdso_data *vd = __arch_get_vdso_data(); 181 u64 hrtimer_res; 182 u32 msk; 183 u64 ns; 184 185 /* Check for negative values or invalid clocks */ 186 if (unlikely((u32) clock >= MAX_CLOCKS)) 187 return -1; 188 189 hrtimer_res = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res); 190 /* 191 * Convert the clockid to a bitmask and use it to check which 192 * clocks are handled in the VDSO directly. 193 */ 194 msk = 1U << clock; 195 if (msk & VDSO_HRES) { 196 /* 197 * Preserves the behaviour of posix_get_hrtimer_res(). 198 */ 199 ns = hrtimer_res; 200 } else if (msk & VDSO_COARSE) { 201 /* 202 * Preserves the behaviour of posix_get_coarse_res(). 203 */ 204 ns = LOW_RES_NSEC; 205 } else if (msk & VDSO_RAW) { 206 /* 207 * Preserves the behaviour of posix_get_hrtimer_res(). 208 */ 209 ns = hrtimer_res; 210 } else { 211 return -1; 212 } 213 214 if (likely(res)) { 215 res->tv_sec = 0; 216 res->tv_nsec = ns; 217 } 218 return 0; 219 } 220 221 static __maybe_unused 222 int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res) 223 { 224 int ret = __cvdso_clock_getres_common(clock, res); 225 226 if (unlikely(ret)) 227 return clock_getres_fallback(clock, res); 228 return 0; 229 } 230 231 #ifdef BUILD_VDSO32 232 static __maybe_unused int 233 __cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res) 234 { 235 struct __kernel_timespec ts; 236 int ret; 237 238 ret = __cvdso_clock_getres_common(clock, &ts); 239 240 if (unlikely(ret)) 241 return clock_getres32_fallback(clock, res); 242 243 if (likely(res)) { 244 res->tv_sec = ts.tv_sec; 245 res->tv_nsec = ts.tv_nsec; 246 } 247 return ret; 248 } 249 #endif /* BUILD_VDSO32 */ 250 #endif /* VDSO_HAS_CLOCK_GETRES */ 251