include/vdso/datapage.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __VDSO_DATAPAGE_H
   3 #define __VDSO_DATAPAGE_H
   4
   5 #ifndef __ASSEMBLY__
   6
   7 #include <linux/bits.h>
   8 #include <linux/time.h>
   9 #include <linux/types.h>
  10
  11 #define VDSO_BASES      (CLOCK_TAI + 1)
  12 #define VDSO_HRES       (BIT(CLOCK_REALTIME)            | \
  13                          BIT(CLOCK_MONOTONIC)           | \
  14                          BIT(CLOCK_BOOTTIME)            | \
  15                          BIT(CLOCK_TAI))
  16 #define VDSO_COARSE     (BIT(CLOCK_REALTIME_COARSE)     | \
  17                          BIT(CLOCK_MONOTONIC_COARSE))
  18 #define VDSO_RAW        (BIT(CLOCK_MONOTONIC_RAW))
  19
  20 #define CS_HRES_COARSE  0
  21 #define CS_RAW          1
  22 #define CS_BASES        (CS_RAW + 1)
  23
  24 /**
  25  * struct vdso_timestamp - basetime per clock_id
  26  * @sec:        seconds
  27  * @nsec:       nanoseconds
  28  *
  29  * There is one vdso_timestamp object in vvar for each vDSO-accelerated
  30  * clock_id. For high-resolution clocks, this encodes the time
  31  * corresponding to vdso_data.cycle_last. For coarse clocks this encodes
  32  * the actual time.
  33  *
  34  * To be noticed that for highres clocks nsec is left-shifted by
  35  * vdso_data.cs[x].shift.
  36  */
  37 struct vdso_timestamp {
  38         u64     sec;
  39         u64     nsec;
  40 };
  41
  42 /**
  43  * struct vdso_data - vdso datapage representation
  44  * @seq:                timebase sequence counter
  45  * @clock_mode:         clock mode
  46  * @cycle_last:         timebase at clocksource init
  47  * @mask:               clocksource mask
  48  * @mult:               clocksource multiplier
  49  * @shift:              clocksource shift
  50  * @basetime[clock_id]: basetime per clock_id
  51  * @tz_minuteswest:     minutes west of Greenwich
  52  * @tz_dsttime:         type of DST correction
  53  * @hrtimer_res:        hrtimer resolution
  54  * @__unused:           unused
  55  *
  56  * vdso_data will be accessed by 64 bit and compat code at the same time
  57  * so we should be careful before modifying this structure.
  58  */
  59 struct vdso_data {
  60         u32                     seq;
  61
  62         s32                     clock_mode;
  63         u64                     cycle_last;
  64         u64                     mask;
  65         u32                     mult;
  66         u32                     shift;
  67
  68         struct vdso_timestamp   basetime[VDSO_BASES];
  69
  70         s32                     tz_minuteswest;
  71         s32                     tz_dsttime;
  72         u32                     hrtimer_res;
  73         u32                     __unused;
  74 };
  75
  76 /*
  77  * We use the hidden visibility to prevent the compiler from generating a GOT
  78  * relocation. Not only is going through a GOT useless (the entry couldn't and
  79  * must not be overridden by another library), it does not even work: the linker
  80  * cannot generate an absolute address to the data page.
  81  *
  82  * With the hidden visibility, the compiler simply generates a PC-relative
  83  * relocation, and this is what we need.
  84  */
  85 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
  86
  87 #endif /* !__ASSEMBLY__ */
  88
  89 #endif /* __VDSO_DATAPAGE_H */