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 #define VCLOCK_TIMENS   UINT_MAX
  25
  26 /**
  27  * struct vdso_timestamp - basetime per clock_id
  28  * @sec:        seconds
  29  * @nsec:       nanoseconds
  30  *
  31  * There is one vdso_timestamp object in vvar for each vDSO-accelerated
  32  * clock_id. For high-resolution clocks, this encodes the time
  33  * corresponding to vdso_data.cycle_last. For coarse clocks this encodes
  34  * the actual time.
  35  *
  36  * To be noticed that for highres clocks nsec is left-shifted by
  37  * vdso_data.cs[x].shift.
  38  */
  39 struct vdso_timestamp {
  40         u64     sec;
  41         u64     nsec;
  42 };
  43
  44 /**
  45  * struct vdso_data - vdso datapage representation
  46  * @seq:                timebase sequence counter
  47  * @clock_mode:         clock mode
  48  * @cycle_last:         timebase at clocksource init
  49  * @mask:               clocksource mask
  50  * @mult:               clocksource multiplier
  51  * @shift:              clocksource shift
  52  * @basetime[clock_id]: basetime per clock_id
  53  * @offset[clock_id]:   time namespace offset per clock_id
  54  * @tz_minuteswest:     minutes west of Greenwich
  55  * @tz_dsttime:         type of DST correction
  56  * @hrtimer_res:        hrtimer resolution
  57  * @__unused:           unused
  58  *
  59  * vdso_data will be accessed by 64 bit and compat code at the same time
  60  * so we should be careful before modifying this structure.
  61  *
  62  * @basetime is used to store the base time for the system wide time getter
  63  * VVAR page.
  64  *
  65  * @offset is used by the special time namespace VVAR pages which are
  66  * installed instead of the real VVAR page. These namespace pages must set
  67  * @seq to 1 and @clock_mode to VLOCK_TIMENS to force the code into the
  68  * time namespace slow path. The namespace aware functions retrieve the
  69  * real system wide VVAR page, read host time and add the per clock offset.
  70  * For clocks which are not affected by time namespace adjustment the
  71  * offset must be zero.
  72  */
  73 struct vdso_data {
  74         u32                     seq;
  75
  76         s32                     clock_mode;
  77         u64                     cycle_last;
  78         u64                     mask;
  79         u32                     mult;
  80         u32                     shift;
  81
  82         union {
  83                 struct vdso_timestamp   basetime[VDSO_BASES];
  84                 struct timens_offset    offset[VDSO_BASES];
  85         };
  86
  87         s32                     tz_minuteswest;
  88         s32                     tz_dsttime;
  89         u32                     hrtimer_res;
  90         u32                     __unused;
  91 };
  92
  93 /*
  94  * We use the hidden visibility to prevent the compiler from generating a GOT
  95  * relocation. Not only is going through a GOT useless (the entry couldn't and
  96  * must not be overridden by another library), it does not even work: the linker
  97  * cannot generate an absolute address to the data page.
  98  *
  99  * With the hidden visibility, the compiler simply generates a PC-relative
 100  * relocation, and this is what we need.
 101  */
 102 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
 103
 104 #endif /* !__ASSEMBLY__ */
 105
 106 #endif /* __VDSO_DATAPAGE_H */