arch/x86/include/asm/vgtod.h

   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 #endif /* _ASM_X86_VGTOD_H */