tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 */
48struct 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 VLOCK_TIMENS to force the code into the
77 * 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 */
82struct 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 */
111extern 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 */