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_TIME_DATA
  23 #include <asm/vdso/time_data.h>
  24 #else
  25 struct arch_vdso_time_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  */
  54 struct 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  * @max_cycles:         maximum cycles which won't overflow 64bit multiplication
  65  * @mask:               clocksource mask
  66  * @mult:               clocksource multiplier
  67  * @shift:              clocksource shift
  68  * @basetime[clock_id]: basetime per clock_id
  69  * @offset[clock_id]:   time namespace offset per clock_id
  70  * @tz_minuteswest:     minutes west of Greenwich
  71  * @tz_dsttime:         type of DST correction
  72  * @hrtimer_res:        hrtimer resolution
  73  * @__unused:           unused
  74  * @arch_data:          architecture specific data (optional, defaults
  75  *                      to an empty struct)
  76  *
  77  * vdso_data will be accessed by 64 bit and compat code at the same time
  78  * so we should be careful before modifying this structure.
  79  *
  80  * The ordering of the struct members is optimized to have fast access to the
  81  * often required struct members which are related to CLOCK_REALTIME and
  82  * CLOCK_MONOTONIC. This information is stored in the first cache lines.
  83  *
  84  * @basetime is used to store the base time for the system wide time getter
  85  * VVAR page.
  86  *
  87  * @offset is used by the special time namespace VVAR pages which are
  88  * installed instead of the real VVAR page. These namespace pages must set
  89  * @seq to 1 and @clock_mode to VDSO_CLOCKMODE_TIMENS to force the code into
  90  * the time namespace slow path. The namespace aware functions retrieve the
  91  * real system wide VVAR page, read host time and add the per clock offset.
  92  * For clocks which are not affected by time namespace adjustment the
  93  * offset must be zero.
  94  */
  95 struct vdso_data {
  96         u32                     seq;
  97
  98         s32                     clock_mode;
  99         u64                     cycle_last;
 100 #ifdef CONFIG_GENERIC_VDSO_OVERFLOW_PROTECT
 101         u64                     max_cycles;
 102 #endif
 103         u64                     mask;
 104         u32                     mult;
 105         u32                     shift;
 106
 107         union {
 108                 struct vdso_timestamp   basetime[VDSO_BASES];
 109                 struct timens_offset    offset[VDSO_BASES];
 110         };
 111
 112         s32                     tz_minuteswest;
 113         s32                     tz_dsttime;
 114         u32                     hrtimer_res;
 115         u32                     __unused;
 116
 117         struct arch_vdso_time_data arch_data;
 118 };
 119
 120 /**
 121  * struct vdso_rng_data - vdso RNG state information
 122  * @generation: counter representing the number of RNG reseeds
 123  * @is_ready:   boolean signaling whether the RNG is initialized
 124  */
 125 struct vdso_rng_data {
 126         u64     generation;
 127         u8      is_ready;
 128 };
 129
 130 /*
 131  * We use the hidden visibility to prevent the compiler from generating a GOT
 132  * relocation. Not only is going through a GOT useless (the entry couldn't and
 133  * must not be overridden by another library), it does not even work: the linker
 134  * cannot generate an absolute address to the data page.
 135  *
 136  * With the hidden visibility, the compiler simply generates a PC-relative
 137  * relocation, and this is what we need.
 138  */
 139 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
 140 extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
 141 extern struct vdso_rng_data _vdso_rng_data __attribute__((visibility("hidden")));
 142
 143 /**
 144  * union vdso_data_store - Generic vDSO data page
 145  */
 146 union vdso_data_store {
 147         struct vdso_data        data[CS_BASES];
 148         u8                      page[1U << CONFIG_PAGE_SHIFT];
 149 };
 150
 151 /*
 152  * The generic vDSO implementation requires that gettimeofday.h
 153  * provides:
 154  * - __arch_get_vdso_data(): to get the vdso datapage.
 155  * - __arch_get_hw_counter(): to get the hw counter based on the
 156  *   clock_mode.
 157  * - gettimeofday_fallback(): fallback for gettimeofday.
 158  * - clock_gettime_fallback(): fallback for clock_gettime.
 159  * - clock_getres_fallback(): fallback for clock_getres.
 160  */
 161 #ifdef ENABLE_COMPAT_VDSO
 162 #include <asm/vdso/compat_gettimeofday.h>
 163 #else
 164 #include <asm/vdso/gettimeofday.h>
 165 #endif /* ENABLE_COMPAT_VDSO */
 166
 167 #endif /* !__ASSEMBLY__ */
 168
 169 #endif /* __VDSO_DATAPAGE_H */