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_TSCPAGE 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 static __always_inline 100 long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 101 { 102 long ret; 103 104 asm ( 105 "mov %%ebx, %%edx \n" 106 "mov %[clock], %%ebx \n" 107 "call __kernel_vsyscall \n" 108 "mov %%edx, %%ebx \n" 109 : "=a" (ret), "=m" (*_ts) 110 : "0" (__NR_clock_gettime64), [clock] "g" (_clkid), "c" (_ts) 111 : "edx"); 112 113 return ret; 114 } 115 116 static __always_inline 117 long gettimeofday_fallback(struct __kernel_old_timeval *_tv, 118 struct timezone *_tz) 119 { 120 long ret; 121 122 asm( 123 "mov %%ebx, %%edx \n" 124 "mov %2, %%ebx \n" 125 "call __kernel_vsyscall \n" 126 "mov %%edx, %%ebx \n" 127 : "=a" (ret) 128 : "0" (__NR_gettimeofday), "g" (_tv), "c" (_tz) 129 : "memory", "edx"); 130 131 return ret; 132 } 133 134 static __always_inline long 135 clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts) 136 { 137 long ret; 138 139 asm ( 140 "mov %%ebx, %%edx \n" 141 "mov %[clock], %%ebx \n" 142 "call __kernel_vsyscall \n" 143 "mov %%edx, %%ebx \n" 144 : "=a" (ret), "=m" (*_ts) 145 : "0" (__NR_clock_getres_time64), [clock] "g" (_clkid), "c" (_ts) 146 : "edx"); 147 148 return ret; 149 } 150 151 #endif 152 153 #ifdef CONFIG_PARAVIRT_CLOCK 154 static u64 vread_pvclock(void) 155 { 156 const struct pvclock_vcpu_time_info *pvti = &pvclock_page.pvti; 157 u32 version; 158 u64 ret; 159 160 /* 161 * Note: The kernel and hypervisor must guarantee that cpu ID 162 * number maps 1:1 to per-CPU pvclock time info. 163 * 164 * Because the hypervisor is entirely unaware of guest userspace 165 * preemption, it cannot guarantee that per-CPU pvclock time 166 * info is updated if the underlying CPU changes or that that 167 * version is increased whenever underlying CPU changes. 168 * 169 * On KVM, we are guaranteed that pvti updates for any vCPU are 170 * atomic as seen by *all* vCPUs. This is an even stronger 171 * guarantee than we get with a normal seqlock. 172 * 173 * On Xen, we don't appear to have that guarantee, but Xen still 174 * supplies a valid seqlock using the version field. 175 * 176 * We only do pvclock vdso timing at all if 177 * PVCLOCK_TSC_STABLE_BIT is set, and we interpret that bit to 178 * mean that all vCPUs have matching pvti and that the TSC is 179 * synced, so we can just look at vCPU 0's pvti. 180 */ 181 182 do { 183 version = pvclock_read_begin(pvti); 184 185 if (unlikely(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT))) 186 return U64_MAX; 187 188 ret = __pvclock_read_cycles(pvti, rdtsc_ordered()); 189 } while (pvclock_read_retry(pvti, version)); 190 191 return ret; 192 } 193 #endif 194 195 #ifdef CONFIG_HYPERV_TSCPAGE 196 static u64 vread_hvclock(void) 197 { 198 return hv_read_tsc_page(&hvclock_page); 199 } 200 #endif 201 202 static inline u64 __arch_get_hw_counter(s32 clock_mode) 203 { 204 if (clock_mode == VCLOCK_TSC) 205 return (u64)rdtsc_ordered(); 206 /* 207 * For any memory-mapped vclock type, we need to make sure that gcc 208 * doesn't cleverly hoist a load before the mode check. Otherwise we 209 * might end up touching the memory-mapped page even if the vclock in 210 * question isn't enabled, which will segfault. Hence the barriers. 211 */ 212 #ifdef CONFIG_PARAVIRT_CLOCK 213 if (clock_mode == VCLOCK_PVCLOCK) { 214 barrier(); 215 return vread_pvclock(); 216 } 217 #endif 218 #ifdef CONFIG_HYPERV_TSCPAGE 219 if (clock_mode == VCLOCK_HVCLOCK) { 220 barrier(); 221 return vread_hvclock(); 222 } 223 #endif 224 return U64_MAX; 225 } 226 227 static __always_inline const struct vdso_data *__arch_get_vdso_data(void) 228 { 229 return __vdso_data; 230 } 231 232 /* 233 * x86 specific delta calculation. 234 * 235 * The regular implementation assumes that clocksource reads are globally 236 * monotonic. The TSC can be slightly off across sockets which can cause 237 * the regular delta calculation (@cycles - @last) to return a huge time 238 * jump. 239 * 240 * Therefore it needs to be verified that @cycles are greater than 241 * @last. If not then use @last, which is the base time of the current 242 * conversion period. 243 * 244 * This variant also removes the masking of the subtraction because the 245 * clocksource mask of all VDSO capable clocksources on x86 is U64_MAX 246 * which would result in a pointless operation. The compiler cannot 247 * optimize it away as the mask comes from the vdso data and is not compile 248 * time constant. 249 */ 250 static __always_inline 251 u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult) 252 { 253 if (cycles > last) 254 return (cycles - last) * mult; 255 return 0; 256 } 257 #define vdso_calc_delta vdso_calc_delta 258 259 #endif /* !__ASSEMBLY__ */ 260 261 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */ 262