LXR linux/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
  11typedef u64 gtod_long_t;
  12#else
  13typedef 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 */
  25struct 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 */
  38struct 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};
  52extern struct vsyscall_gtod_data vsyscall_gtod_data;
  53
  54extern int vclocks_used;
  55static inline bool vclock_was_used(int vclock)
  56{
  57        return READ_ONCE(vclocks_used) & (1 << vclock);
  58}
  59
  60static inline unsigned int gtod_read_begin(const struct vsyscall_gtod_data *s)
  61{
  62        unsigned int ret;
  63
  64repeat:
  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
  74static 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
  81static inline void gtod_write_begin(struct vsyscall_gtod_data *s)
  82{
  83        ++s->seq;
  84        smp_wmb();
  85}
  86
  87static 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 */
  94