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 25 #define VDSO_HAS_TIME 1 26 27 #define VDSO_HAS_CLOCK_GETRES 1 28 29 /* 30 * Declare the memory-mapped vclock data pages. These come from hypervisors. 31 * If we ever reintroduce something like direct access to an MMIO clock like 32 * the HPET again, it will go here as well. 33 * 34 * A load from any of these pages will segfault if the clock in question is 35 * disabled, so appropriate compiler barriers and checks need to be used 36 * to prevent stray loads. 37 * 38 * These declarations MUST NOT be const. The compiler will assume that 39 * an extern const variable has genuinely constant contents, and the 40 * resulting code won't work, since the whole point is that these pages 41 * change over time, possibly while we're accessing them. 42 */ 43 44 #ifdef CONFIG_PARAVIRT_CLOCK 45 /* 46 * This is the vCPU 0 pvclock page. We only use pvclock from the vDSO 47 * if the hypervisor tells us that all vCPUs can get valid data from the 48 * vCPU 0 page. 49 */ 50 extern struct pvclock_vsyscall_time_info pvclock_page 51 __attribute__((visibility("hidden"))); 52 #endif 53 54 #ifdef CONFIG_HYPERV_TIMER 55 extern struct ms_hyperv_tsc_page hvclock_page 56 __attribute__((visibility("hidden"))); 57 #endif 58 59 #ifndef BUILD_VDSO32 60 61 static __always_inline 62 long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 63 { 64 long ret; 65 66 asm ("syscall" : "=a" (ret), "=m" (*_ts) : 67 "0" (__NR_clock_gettime), "D" (_clkid), "S" (_ts) : 68 "rcx", "r11"); 69 70 return ret; 71 } 72 73 static __always_inline 74 long gettimeofday_fallback(struct __kernel_old_timeval *_tv, 75 struct timezone *_tz) 76 { 77 long ret; 78 79 asm("syscall" : "=a" (ret) : 80 "0" (__NR_gettimeofday), "D" (_tv), "S" (_tz) : "memory"); 81 82 return ret; 83 } 84 85 static __always_inline 86 long clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 87 { 88 long ret; 89 90 asm ("syscall" : "=a" (ret), "=m" (*_ts) : 91 "0" (__NR_clock_getres), "D" (_clkid), "S" (_ts) : 92 "rcx", "r11"); 93 94 return ret; 95 } 96 97 #else 98 99 #define VDSO_HAS_32BIT_FALLBACK 1 100 101 static __always_inline 102 long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 103 { 104 long ret; 105 106 asm ( 107 "mov %%ebx, %%edx \n" 108 "mov %[clock], %%ebx \n" 109 "call __kernel_vsyscall \n" 110 "mov %%edx, %%ebx \n" 111 : "=a" (ret), "=m" (*_ts) 112 : "0" (__NR_clock_gettime64), [clock] "g" (_clkid), "c" (_ts) 113 : "edx"); 114 115 return ret; 116 } 117 118 static __always_inline 119 long clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts) 120 { 121 long ret; 122 123 asm ( 124 "mov %%ebx, %%edx \n" 125 "mov %[clock], %%ebx \n" 126 "call __kernel_vsyscall \n" 127 "mov %%edx, %%ebx \n" 128 : "=a" (ret), "=m" (*_ts) 129 : "0" (__NR_clock_gettime), [clock] "g" (_clkid), "c" (_ts) 130 : "edx"); 131 132 return ret; 133 } 134 135 static __always_inline 136 long gettimeofday_fallback(struct __kernel_old_timeval *_tv, 137 struct timezone *_tz) 138 { 139 long ret; 140 141 asm( 142 "mov %%ebx, %%edx \n" 143 "mov %2, %%ebx \n" 144 "call __kernel_vsyscall \n" 145 "mov %%edx, %%ebx \n" 146 : "=a" (ret) 147 : "0" (__NR_gettimeofday), "g" (_tv), "c" (_tz) 148 : "memory", "edx"); 149 150 return ret; 151 } 152 153 static __always_inline long 154 clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 155 { 156 long ret; 157 158 asm ( 159 "mov %%ebx, %%edx \n" 160 "mov %[clock], %%ebx \n" 161 "call __kernel_vsyscall \n" 162 "mov %%edx, %%ebx \n" 163 : "=a" (ret), "=m" (*_ts) 164 : "0" (__NR_clock_getres_time64), [clock] "g" (_clkid), "c" (_ts) 165 : "edx"); 166 167 return ret; 168 } 169 170 static __always_inline 171 long clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts) 172 { 173 long ret; 174 175 asm ( 176 "mov %%ebx, %%edx \n" 177 "mov %[clock], %%ebx \n" 178 "call __kernel_vsyscall \n" 179 "mov %%edx, %%ebx \n" 180 : "=a" (ret), "=m" (*_ts) 181 : "0" (__NR_clock_getres), [clock] "g" (_clkid), "c" (_ts) 182 : "edx"); 183 184 return ret; 185 } 186 187 #endif 188 189 #ifdef CONFIG_PARAVIRT_CLOCK 190 static u64 vread_pvclock(void) 191 { 192 const struct pvclock_vcpu_time_info *pvti = &pvclock_page.pvti; 193 u32 version; 194 u64 ret; 195 196 /* 197 * Note: The kernel and hypervisor must guarantee that cpu ID 198 * number maps 1:1 to per-CPU pvclock time info. 199 * 200 * Because the hypervisor is entirely unaware of guest userspace 201 * preemption, it cannot guarantee that per-CPU pvclock time 202 * info is updated if the underlying CPU changes or that that 203 * version is increased whenever underlying CPU changes. 204 * 205 * On KVM, we are guaranteed that pvti updates for any vCPU are 206 * atomic as seen by *all* vCPUs. This is an even stronger 207 * guarantee than we get with a normal seqlock. 208 * 209 * On Xen, we don't appear to have that guarantee, but Xen still 210 * supplies a valid seqlock using the version field. 211 * 212 * We only do pvclock vdso timing at all if 213 * PVCLOCK_TSC_STABLE_BIT is set, and we interpret that bit to 214 * mean that all vCPUs have matching pvti and that the TSC is 215 * synced, so we can just look at vCPU 0's pvti. 216 */ 217 218 do { 219 version = pvclock_read_begin(pvti); 220 221 if (unlikely(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT))) 222 return U64_MAX; 223 224 ret = __pvclock_read_cycles(pvti, rdtsc_ordered()); 225 } while (pvclock_read_retry(pvti, version)); 226 227 return ret; 228 } 229 #endif 230 231 #ifdef CONFIG_HYPERV_TIMER 232 static u64 vread_hvclock(void) 233 { 234 return hv_read_tsc_page(&hvclock_page); 235 } 236 #endif 237 238 static inline u64 __arch_get_hw_counter(s32 clock_mode) 239 { 240 if (clock_mode == VCLOCK_TSC) 241 return (u64)rdtsc_ordered(); 242 /* 243 * For any memory-mapped vclock type, we need to make sure that gcc 244 * doesn't cleverly hoist a load before the mode check. Otherwise we 245 * might end up touching the memory-mapped page even if the vclock in 246 * question isn't enabled, which will segfault. Hence the barriers. 247 */ 248 #ifdef CONFIG_PARAVIRT_CLOCK 249 if (clock_mode == VCLOCK_PVCLOCK) { 250 barrier(); 251 return vread_pvclock(); 252 } 253 #endif 254 #ifdef CONFIG_HYPERV_TIMER 255 if (clock_mode == VCLOCK_HVCLOCK) { 256 barrier(); 257 return vread_hvclock(); 258 } 259 #endif 260 return U64_MAX; 261 } 262 263 static __always_inline const struct vdso_data *__arch_get_vdso_data(void) 264 { 265 return __vdso_data; 266 } 267 268 /* 269 * x86 specific delta calculation. 270 * 271 * The regular implementation assumes that clocksource reads are globally 272 * monotonic. The TSC can be slightly off across sockets which can cause 273 * the regular delta calculation (@cycles - @last) to return a huge time 274 * jump. 275 * 276 * Therefore it needs to be verified that @cycles are greater than 277 * @last. If not then use @last, which is the base time of the current 278 * conversion period. 279 * 280 * This variant also removes the masking of the subtraction because the 281 * clocksource mask of all VDSO capable clocksources on x86 is U64_MAX 282 * which would result in a pointless operation. The compiler cannot 283 * optimize it away as the mask comes from the vdso data and is not compile 284 * time constant. 285 */ 286 static __always_inline 287 u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult) 288 { 289 if (cycles > last) 290 return (cycles - last) * mult; 291 return 0; 292 } 293 #define vdso_calc_delta vdso_calc_delta 294 295 #endif /* !__ASSEMBLY__ */ 296 297 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */ 298