LXR linux/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#ifdef CONFIG_ARCH_HAS_VDSO_DATA
  23#include <asm/vdso/data.h>
  24#else
  25struct arch_vdso_data {};
  26#endif
  27
  28#define VDSO_BASES      (CLOCK_TAI + 1)
  29#define VDSO_HRES       (BIT(CLOCK_REALTIME)            | \
  30                         BIT(CLOCK_MONOTONIC)           | \
  31                         BIT(CLOCK_BOOTTIME)            | \
  32                         BIT(CLOCK_TAI))
  33#define VDSO_COARSE     (BIT(CLOCK_REALTIME_COARSE)     | \
  34                         BIT(CLOCK_MONOTONIC_COARSE))
  35#define VDSO_RAW        (BIT(CLOCK_MONOTONIC_RAW))
  36
  37#define CS_HRES_COARSE  0
  38#define CS_RAW          1
  39#define CS_BASES        (CS_RAW + 1)
  40
  41/**
  42 * struct vdso_timestamp - basetime per clock_id
  43 * @sec:        seconds
  44 * @nsec:       nanoseconds
  45 *
  46 * There is one vdso_timestamp object in vvar for each vDSO-accelerated
  47 * clock_id. For high-resolution clocks, this encodes the time
  48 * corresponding to vdso_data.cycle_last. For coarse clocks this encodes
  49 * the actual time.
  50 *
  51 * To be noticed that for highres clocks nsec is left-shifted by
  52 * vdso_data.cs[x].shift.
  53 */
  54struct vdso_timestamp {
  55        u64     sec;
  56        u64     nsec;
  57};
  58
  59/**
  60 * struct vdso_data - vdso datapage representation
  61 * @seq:                timebase sequence counter
  62 * @clock_mode:         clock mode
  63 * @cycle_last:         timebase at clocksource init
  64 * @mask:               clocksource mask
  65 * @mult:               clocksource multiplier
  66 * @shift:              clocksource shift
  67 * @basetime[clock_id]: basetime per clock_id
  68 * @offset[clock_id]:   time namespace offset per clock_id
  69 * @tz_minuteswest:     minutes west of Greenwich
  70 * @tz_dsttime:         type of DST correction
  71 * @hrtimer_res:        hrtimer resolution
  72 * @__unused:           unused
  73 * @arch_data:          architecture specific data (optional, defaults
  74 *                      to an empty struct)
  75 *
  76 * vdso_data will be accessed by 64 bit and compat code at the same time
  77 * so we should be careful before modifying this structure.
  78 *
  79 * @basetime is used to store the base time for the system wide time getter
  80 * VVAR page.
  81 *
  82 * @offset is used by the special time namespace VVAR pages which are
  83 * installed instead of the real VVAR page. These namespace pages must set
  84 * @seq to 1 and @clock_mode to VDSO_CLOCKMODE_TIMENS to force the code into
  85 * the time namespace slow path. The namespace aware functions retrieve the
  86 * real system wide VVAR page, read host time and add the per clock offset.
  87 * For clocks which are not affected by time namespace adjustment the
  88 * offset must be zero.
  89 */
  90struct vdso_data {
  91        u32                     seq;
  92
  93        s32                     clock_mode;
  94        u64                     cycle_last;
  95        u64                     mask;
  96        u32                     mult;
  97        u32                     shift;
  98
  99        union {
 100                struct vdso_timestamp   basetime[VDSO_BASES];
 101                struct timens_offset    offset[VDSO_BASES];
 102        };
 103
 104        s32                     tz_minuteswest;
 105        s32                     tz_dsttime;
 106        u32                     hrtimer_res;
 107        u32                     __unused;
 108
 109        struct arch_vdso_data   arch_data;
 110};
 111
 112/*
 113 * We use the hidden visibility to prevent the compiler from generating a GOT
 114 * relocation. Not only is going through a GOT useless (the entry couldn't and
 115 * must not be overridden by another library), it does not even work: the linker
 116 * cannot generate an absolute address to the data page.
 117 *
 118 * With the hidden visibility, the compiler simply generates a PC-relative
 119 * relocation, and this is what we need.
 120 */
 121extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
 122extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
 123
 124/*
 125 * The generic vDSO implementation requires that gettimeofday.h
 126 * provides:
 127 * - __arch_get_vdso_data(): to get the vdso datapage.
 128 * - __arch_get_hw_counter(): to get the hw counter based on the
 129 *   clock_mode.
 130 * - gettimeofday_fallback(): fallback for gettimeofday.
 131 * - clock_gettime_fallback(): fallback for clock_gettime.
 132 * - clock_getres_fallback(): fallback for clock_getres.
 133 */
 134#ifdef ENABLE_COMPAT_VDSO
 135#include <asm/vdso/compat_gettimeofday.h>
 136#else
 137#include <asm/vdso/gettimeofday.h>
 138#endif /* ENABLE_COMPAT_VDSO */
 139
 140#endif /* !__ASSEMBLY__ */
 141
 142#endif /* __VDSO_DATAPAGE_H */
 143