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