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
25 struct 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 */
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_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 */
170
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