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/compiler.h>
   8 #include <uapi/linux/time.h>
   9 #include <uapi/linux/types.h>
  10 #include <uapi/asm-generic/errno-base.h>
  11
  12 #include <vdso/bits.h>
  13 #include <vdso/clocksource.h>
  14 #include <vdso/ktime.h>
  15 #include <vdso/limits.h>
  16 #include <vdso/math64.h>
  17 #include <vdso/processor.h>
  18 #include <vdso/time.h>
  19 #include <vdso/time32.h>
  20 #include <vdso/time64.h>
  21
  22 #define VDSO_BASES      (CLOCK_TAI + 1)
  23 #define VDSO_HRES       (BIT(CLOCK_REALTIME)            | \
  24                          BIT(CLOCK_MONOTONIC)           | \
  25                          BIT(CLOCK_BOOTTIME)            | \
  26                          BIT(CLOCK_TAI))
  27 #define VDSO_COARSE     (BIT(CLOCK_REALTIME_COARSE)     | \
  28                          BIT(CLOCK_MONOTONIC_COARSE))
  29 #define VDSO_RAW        (BIT(CLOCK_MONOTONIC_RAW))
  30
  31 #define CS_HRES_COARSE  0
  32 #define CS_RAW          1
  33 #define CS_BASES        (CS_RAW + 1)
  34
  35 /**
  36  * struct vdso_timestamp - basetime per clock_id
  37  * @sec:        seconds
  38  * @nsec:       nanoseconds
  39  *
  40  * There is one vdso_timestamp object in vvar for each vDSO-accelerated
  41  * clock_id. For high-resolution clocks, this encodes the time
  42  * corresponding to vdso_data.cycle_last. For coarse clocks this encodes
  43  * the actual time.
  44  *
  45  * To be noticed that for highres clocks nsec is left-shifted by
  46  * vdso_data.cs[x].shift.
  47  */
  48 struct vdso_timestamp {
  49         u64     sec;
  50         u64     nsec;
  51 };
  52
  53 /**
  54  * struct vdso_data - vdso datapage representation
  55  * @seq:                timebase sequence counter
  56  * @clock_mode:         clock mode
  57  * @cycle_last:         timebase at clocksource init
  58  * @mask:               clocksource mask
  59  * @mult:               clocksource multiplier
  60  * @shift:              clocksource shift
  61  * @basetime[clock_id]: basetime per clock_id
  62  * @offset[clock_id]:   time namespace offset per clock_id
  63  * @tz_minuteswest:     minutes west of Greenwich
  64  * @tz_dsttime:         type of DST correction
  65  * @hrtimer_res:        hrtimer resolution
  66  * @__unused:           unused
  67  *
  68  * vdso_data will be accessed by 64 bit and compat code at the same time
  69  * so we should be careful before modifying this structure.
  70  *
  71  * @basetime is used to store the base time for the system wide time getter
  72  * VVAR page.
  73  *
  74  * @offset is used by the special time namespace VVAR pages which are
  75  * installed instead of the real VVAR page. These namespace pages must set
  76  * @seq to 1 and @clock_mode to VDSO_CLOCKMODE_TIMENS to force the code into
  77  * the time namespace slow path. The namespace aware functions retrieve the
  78  * real system wide VVAR page, read host time and add the per clock offset.
  79  * For clocks which are not affected by time namespace adjustment the
  80  * offset must be zero.
  81  */
  82 struct vdso_data {
  83         u32                     seq;
  84
  85         s32                     clock_mode;
  86         u64                     cycle_last;
  87         u64                     mask;
  88         u32                     mult;
  89         u32                     shift;
  90
  91         union {
  92                 struct vdso_timestamp   basetime[VDSO_BASES];
  93                 struct timens_offset    offset[VDSO_BASES];
  94         };
  95
  96         s32                     tz_minuteswest;
  97         s32                     tz_dsttime;
  98         u32                     hrtimer_res;
  99         u32                     __unused;
 100 };
 101
 102 /*
 103  * We use the hidden visibility to prevent the compiler from generating a GOT
 104  * relocation. Not only is going through a GOT useless (the entry couldn't and
 105  * must not be overridden by another library), it does not even work: the linker
 106  * cannot generate an absolute address to the data page.
 107  *
 108  * With the hidden visibility, the compiler simply generates a PC-relative
 109  * relocation, and this is what we need.
 110  */
 111 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
 112
 113 /*
 114  * The generic vDSO implementation requires that gettimeofday.h
 115  * provides:
 116  * - __arch_get_vdso_data(): to get the vdso datapage.
 117  * - __arch_get_hw_counter(): to get the hw counter based on the
 118  *   clock_mode.
 119  * - gettimeofday_fallback(): fallback for gettimeofday.
 120  * - clock_gettime_fallback(): fallback for clock_gettime.
 121  * - clock_getres_fallback(): fallback for clock_getres.
 122  */
 123 #ifdef ENABLE_COMPAT_VDSO
 124 #include <asm/vdso/compat_gettimeofday.h>
 125 #else
 126 #include <asm/vdso/gettimeofday.h>
 127 #endif /* ENABLE_COMPAT_VDSO */
 128
 129 #endif /* !__ASSEMBLY__ */
 130
 131 #endif /* __VDSO_DATAPAGE_H */