1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Fast user context implementation of clock_gettime, gettimeofday, and time. 4 * 5 * Copyright (C) 2019 ARM Limited. 6 * Copyright 2006 Andi Kleen, SUSE Labs. 7 * 32 Bit compat layer by Stefani Seibold <stefani@seibold.net> 8 * sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany 9 */ 10 #ifndef __ASM_VDSO_GETTIMEOFDAY_H 11 #define __ASM_VDSO_GETTIMEOFDAY_H 12 13 #ifndef __ASSEMBLY__ 14 15 #include <uapi/linux/time.h> 16 #include <asm/vgtod.h> 17 #include <asm/vvar.h> 18 #include <asm/unistd.h> 19 #include <asm/msr.h> 20 #include <asm/pvclock.h> 21 #include <clocksource/hyperv_timer.h> 22 23 #define __vdso_data (VVAR(_vdso_data)) 24 #define __timens_vdso_data (TIMENS(_vdso_data)) 25 26 #define VDSO_HAS_TIME 1 27 28 #define VDSO_HAS_CLOCK_GETRES 1 29 30 /* 31 * Declare the memory-mapped vclock data pages. These come from hypervisors. 32 * If we ever reintroduce something like direct access to an MMIO clock like 33 * the HPET again, it will go here as well. 34 * 35 * A load from any of these pages will segfault if the clock in question is 36 * disabled, so appropriate compiler barriers and checks need to be used 37 * to prevent stray loads. 38 * 39 * These declarations MUST NOT be const. The compiler will assume that 40 * an extern const variable has genuinely constant contents, and the 41 * resulting code won't work, since the whole point is that these pages 42 * change over time, possibly while we're accessing them. 43 */ 44 45 #ifdef CONFIG_PARAVIRT_CLOCK 46 /* 47 * This is the vCPU 0 pvclock page. We only use pvclock from the vDSO 48 * if the hypervisor tells us that all vCPUs can get valid data from the 49 * vCPU 0 page. 50 */ 51 extern struct pvclock_vsyscall_time_info pvclock_page 52 __attribute__((visibility("hidden"))); 53 #endif 54 55 #ifdef CONFIG_HYPERV_TIMER 56 extern struct ms_hyperv_tsc_page hvclock_page 57 __attribute__((visibility("hidden"))); 58 #endif 59 60 #ifdef CONFIG_TIME_NS 61 static __always_inline 62 const struct vdso_data *__arch_get_timens_vdso_data(const struct vdso_data *vd) 63 { 64 return __timens_vdso_data; 65 } 66 #endif 67 68 #ifndef BUILD_VDSO32 69 70 static __always_inline 71 long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 72 { 73 long ret; 74 75 asm ("syscall" : "=a" (ret), "=m" (*_ts) : 76 "0" (__NR_clock_gettime), "D" (_clkid), "S" (_ts) : 77 "rcx", "r11"); 78 79 return ret; 80 } 81 82 static __always_inline 83 long gettimeofday_fallback(struct __kernel_old_timeval *_tv, 84 struct timezone *_tz) 85 { 86 long ret; 87 88 asm("syscall" : "=a" (ret) : 89 "0" (__NR_gettimeofday), "D" (_tv), "S" (_tz) : "memory"); 90 91 return ret; 92 } 93 94 static __always_inline 95 long clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 96 { 97 long ret; 98 99 asm ("syscall" : "=a" (ret), "=m" (*_ts) : 100 "0" (__NR_clock_getres), "D" (_clkid), "S" (_ts) : 101 "rcx", "r11"); 102 103 return ret; 104 } 105 106 #else 107 108 static __always_inline 109 long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 110 { 111 long ret; 112 113 asm ( 114 "mov %%ebx, %%edx \n" 115 "mov %[clock], %%ebx \n" 116 "call __kernel_vsyscall \n" 117 "mov %%edx, %%ebx \n" 118 : "=a" (ret), "=m" (*_ts) 119 : "0" (__NR_clock_gettime64), [clock] "g" (_clkid), "c" (_ts) 120 : "edx"); 121 122 return ret; 123 } 124 125 static __always_inline 126 long clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts) 127 { 128 long ret; 129 130 asm ( 131 "mov %%ebx, %%edx \n" 132 "mov %[clock], %%ebx \n" 133 "call __kernel_vsyscall \n" 134 "mov %%edx, %%ebx \n" 135 : "=a" (ret), "=m" (*_ts) 136 : "0" (__NR_clock_gettime), [clock] "g" (_clkid), "c" (_ts) 137 : "edx"); 138 139 return ret; 140 } 141 142 static __always_inline 143 long gettimeofday_fallback(struct __kernel_old_timeval *_tv, 144 struct timezone *_tz) 145 { 146 long ret; 147 148 asm( 149 "mov %%ebx, %%edx \n" 150 "mov %2, %%ebx \n" 151 "call __kernel_vsyscall \n" 152 "mov %%edx, %%ebx \n" 153 : "=a" (ret) 154 : "0" (__NR_gettimeofday), "g" (_tv), "c" (_tz) 155 : "memory", "edx"); 156 157 return ret; 158 } 159 160 static __always_inline long 161 clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 162 { 163 long ret; 164 165 asm ( 166 "mov %%ebx, %%edx \n" 167 "mov %[clock], %%ebx \n" 168 "call __kernel_vsyscall \n" 169 "mov %%edx, %%ebx \n" 170 : "=a" (ret), "=m" (*_ts) 171 : "0" (__NR_clock_getres_time64), [clock] "g" (_clkid), "c" (_ts) 172 : "edx"); 173 174 return ret; 175 } 176 177 static __always_inline 178 long clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts) 179 { 180 long ret; 181 182 asm ( 183 "mov %%ebx, %%edx \n" 184 "mov %[clock], %%ebx \n" 185 "call __kernel_vsyscall \n" 186 "mov %%edx, %%ebx \n" 187 : "=a" (ret), "=m" (*_ts) 188 : "0" (__NR_clock_getres), [clock] "g" (_clkid), "c" (_ts) 189 : "edx"); 190 191 return ret; 192 } 193 194 #endif 195 196 #ifdef CONFIG_PARAVIRT_CLOCK 197 static u64 vread_pvclock(void) 198 { 199 const struct pvclock_vcpu_time_info *pvti = &pvclock_page.pvti; 200 u32 version; 201 u64 ret; 202 203 /* 204 * Note: The kernel and hypervisor must guarantee that cpu ID 205 * number maps 1:1 to per-CPU pvclock time info. 206 * 207 * Because the hypervisor is entirely unaware of guest userspace 208 * preemption, it cannot guarantee that per-CPU pvclock time 209 * info is updated if the underlying CPU changes or that that 210 * version is increased whenever underlying CPU changes. 211 * 212 * On KVM, we are guaranteed that pvti updates for any vCPU are 213 * atomic as seen by *all* vCPUs. This is an even stronger 214 * guarantee than we get with a normal seqlock. 215 * 216 * On Xen, we don't appear to have that guarantee, but Xen still 217 * supplies a valid seqlock using the version field. 218 * 219 * We only do pvclock vdso timing at all if 220 * PVCLOCK_TSC_STABLE_BIT is set, and we interpret that bit to 221 * mean that all vCPUs have matching pvti and that the TSC is 222 * synced, so we can just look at vCPU 0's pvti. 223 */ 224 225 do { 226 version = pvclock_read_begin(pvti); 227 228 if (unlikely(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT))) 229 return U64_MAX; 230 231 ret = __pvclock_read_cycles(pvti, rdtsc_ordered()); 232 } while (pvclock_read_retry(pvti, version)); 233 234 return ret & S64_MAX; 235 } 236 #endif 237 238 #ifdef CONFIG_HYPERV_TIMER 239 static u64 vread_hvclock(void) 240 { 241 u64 tsc, time; 242 243 if (hv_read_tsc_page_tsc(&hvclock_page, &tsc, &time)) 244 return time & S64_MAX; 245 246 return U64_MAX; 247 } 248 #endif 249 250 static inline u64 __arch_get_hw_counter(s32 clock_mode, 251 const struct vdso_data *vd) 252 { 253 if (likely(clock_mode == VDSO_CLOCKMODE_TSC)) 254 return (u64)rdtsc_ordered() & S64_MAX; 255 /* 256 * For any memory-mapped vclock type, we need to make sure that gcc 257 * doesn't cleverly hoist a load before the mode check. Otherwise we 258 * might end up touching the memory-mapped page even if the vclock in 259 * question isn't enabled, which will segfault. Hence the barriers. 260 */ 261 #ifdef CONFIG_PARAVIRT_CLOCK 262 if (clock_mode == VDSO_CLOCKMODE_PVCLOCK) { 263 barrier(); 264 return vread_pvclock(); 265 } 266 #endif 267 #ifdef CONFIG_HYPERV_TIMER 268 if (clock_mode == VDSO_CLOCKMODE_HVCLOCK) { 269 barrier(); 270 return vread_hvclock(); 271 } 272 #endif 273 return U64_MAX; 274 } 275 276 static __always_inline const struct vdso_data *__arch_get_vdso_data(void) 277 { 278 return __vdso_data; 279 } 280 281 static inline bool arch_vdso_clocksource_ok(const struct vdso_data *vd) 282 { 283 return true; 284 } 285 #define vdso_clocksource_ok arch_vdso_clocksource_ok 286 287 /* 288 * Clocksource read value validation to handle PV and HyperV clocksources 289 * which can be invalidated asynchronously and indicate invalidation by 290 * returning U64_MAX, which can be effectively tested by checking for a 291 * negative value after casting it to s64. 292 * 293 * This effectively forces a S64_MAX mask on the calculations, unlike the 294 * U64_MAX mask normally used by x86 clocksources. 295 */ 296 static inline bool arch_vdso_cycles_ok(u64 cycles) 297 { 298 return (s64)cycles >= 0; 299 } 300 #define vdso_cycles_ok arch_vdso_cycles_ok 301 302 /* 303 * x86 specific delta calculation. 304 * 305 * The regular implementation assumes that clocksource reads are globally 306 * monotonic. The TSC can be slightly off across sockets which can cause 307 * the regular delta calculation (@cycles - @last) to return a huge time 308 * jump. 309 * 310 * Therefore it needs to be verified that @cycles are greater than 311 * @last. If not then use @last, which is the base time of the current 312 * conversion period. 313 * 314 * This variant also uses a custom mask because while the clocksource mask of 315 * all the VDSO capable clocksources on x86 is U64_MAX, the above code uses 316 * U64_MASK as an exception value, additionally arch_vdso_cycles_ok() above 317 * declares everything with the MSB/Sign-bit set as invalid. Therefore the 318 * effective mask is S64_MAX. 319 */ 320 static __always_inline 321 u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult) 322 { 323 /* 324 * Due to the MSB/Sign-bit being used as invald marker (see 325 * arch_vdso_cycles_valid() above), the effective mask is S64_MAX. 326 */ 327 u64 delta = (cycles - last) & S64_MAX; 328 329 /* 330 * Due to the above mentioned TSC wobbles, filter out negative motion. 331 * Per the above masking, the effective sign bit is now bit 62. 332 */ 333 if (unlikely(delta & (1ULL << 62))) 334 return 0; 335 336 return delta * mult; 337 } 338 #define vdso_calc_delta vdso_calc_delta 339 340 int __vdso_clock_gettime64(clockid_t clock, struct __kernel_timespec *ts); 341 342 #endif /* !__ASSEMBLY__ */ 343 344 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */ 345