1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_VGTOD_H 3 #define _ASM_X86_VGTOD_H 4 5 #include <linux/compiler.h> 6 #include <linux/clocksource.h> 7 8 #include <uapi/linux/time.h> 9 10 #ifdef BUILD_VDSO32_64 11 typedef u64 gtod_long_t; 12 #else 13 typedef unsigned long gtod_long_t; 14 #endif 15 16 /* 17 * There is one of these objects in the vvar page for each 18 * vDSO-accelerated clockid. For high-resolution clocks, this encodes 19 * the time corresponding to vsyscall_gtod_data.cycle_last. For coarse 20 * clocks, this encodes the actual time. 21 * 22 * To confuse the reader, for high-resolution clocks, nsec is left-shifted 23 * by vsyscall_gtod_data.shift. 24 */ 25 struct vgtod_ts { 26 u64 sec; 27 u64 nsec; 28 }; 29 30 #define VGTOD_BASES (CLOCK_TAI + 1) 31 #define VGTOD_HRES (BIT(CLOCK_REALTIME) | BIT(CLOCK_MONOTONIC) | BIT(CLOCK_TAI)) 32 #define VGTOD_COARSE (BIT(CLOCK_REALTIME_COARSE) | BIT(CLOCK_MONOTONIC_COARSE)) 33 34 /* 35 * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time 36 * so be carefull by modifying this structure. 37 */ 38 struct vsyscall_gtod_data { 39 unsigned int seq; 40 41 int vclock_mode; 42 u64 cycle_last; 43 u64 mask; 44 u32 mult; 45 u32 shift; 46 47 struct vgtod_ts basetime[VGTOD_BASES]; 48 49 int tz_minuteswest; 50 int tz_dsttime; 51 }; 52 extern struct vsyscall_gtod_data vsyscall_gtod_data; 53 54 extern int vclocks_used; 55 static inline bool vclock_was_used(int vclock) 56 { 57 return READ_ONCE(vclocks_used) & (1 << vclock); 58 } 59 60 static inline unsigned int gtod_read_begin(const struct vsyscall_gtod_data *s) 61 { 62 unsigned int ret; 63 64 repeat: 65 ret = READ_ONCE(s->seq); 66 if (unlikely(ret & 1)) { 67 cpu_relax(); 68 goto repeat; 69 } 70 smp_rmb(); 71 return ret; 72 } 73 74 static inline int gtod_read_retry(const struct vsyscall_gtod_data *s, 75 unsigned int start) 76 { 77 smp_rmb(); 78 return unlikely(s->seq != start); 79 } 80 81 static inline void gtod_write_begin(struct vsyscall_gtod_data *s) 82 { 83 ++s->seq; 84 smp_wmb(); 85 } 86 87 static inline void gtod_write_end(struct vsyscall_gtod_data *s) 88 { 89 smp_wmb(); 90 ++s->seq; 91 } 92 93 #ifdef CONFIG_X86_64 94 95 #define VGETCPU_CPU_MASK 0xfff 96 97 static inline unsigned int __getcpu(void) 98 { 99 unsigned int p; 100 101 /* 102 * Load per CPU data from GDT. LSL is faster than RDTSCP and 103 * works on all CPUs. This is volatile so that it orders 104 * correctly wrt barrier() and to keep gcc from cleverly 105 * hoisting it out of the calling function. 106 * 107 * If RDPID is available, use it. 108 */ 109 alternative_io ("lsl %[seg],%[p]", 110 ".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */ 111 X86_FEATURE_RDPID, 112 [p] "=a" (p), [seg] "r" (__PER_CPU_SEG)); 113 114 return p; 115 } 116 117 #endif /* CONFIG_X86_64 */ 118 119 #endif /* _ASM_X86_VGTOD_H */ 120