include/vdso/datapage.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef __VDSO_DATAPAGE_H
0003 #define __VDSO_DATAPAGE_H
0004
0005 #ifndef __ASSEMBLY__
0006
0007 #include <linux/compiler.h>
0008 #include <uapi/linux/time.h>
0009 #include <uapi/linux/types.h>
0010 #include <uapi/asm-generic/errno-base.h>
0011
0012 #include <vdso/bits.h>
0013 #include <vdso/clocksource.h>
0014 #include <vdso/ktime.h>
0015 #include <vdso/limits.h>
0016 #include <vdso/math64.h>
0017 #include <vdso/processor.h>
0018 #include <vdso/time.h>
0019 #include <vdso/time32.h>
0020 #include <vdso/time64.h>
0021
0022 #ifdef CONFIG_ARCH_HAS_VDSO_DATA
0023 #include <asm/vdso/data.h>
0024 #else
0025 struct arch_vdso_data {};
0026 #endif
0027
0028 #define VDSO_BASES  (CLOCK_TAI + 1)
0029 #define VDSO_HRES   (BIT(CLOCK_REALTIME)        | \
0030              BIT(CLOCK_MONOTONIC)       | \
0031              BIT(CLOCK_BOOTTIME)        | \
0032              BIT(CLOCK_TAI))
0033 #define VDSO_COARSE (BIT(CLOCK_REALTIME_COARSE) | \
0034              BIT(CLOCK_MONOTONIC_COARSE))
0035 #define VDSO_RAW    (BIT(CLOCK_MONOTONIC_RAW))
0036
0037 #define CS_HRES_COARSE  0
0038 #define CS_RAW      1
0039 #define CS_BASES    (CS_RAW + 1)
0040
0041 /**
0042  * struct vdso_timestamp - basetime per clock_id
0043  * @sec:    seconds
0044  * @nsec:   nanoseconds
0045  *
0046  * There is one vdso_timestamp object in vvar for each vDSO-accelerated
0047  * clock_id. For high-resolution clocks, this encodes the time
0048  * corresponding to vdso_data.cycle_last. For coarse clocks this encodes
0049  * the actual time.
0050  *
0051  * To be noticed that for highres clocks nsec is left-shifted by
0052  * vdso_data.cs[x].shift.
0053  */
0054 struct vdso_timestamp {
0055     u64 sec;
0056     u64 nsec;
0057 };
0058
0059 /**
0060  * struct vdso_data - vdso datapage representation
0061  * @seq:        timebase sequence counter
0062  * @clock_mode:     clock mode
0063  * @cycle_last:     timebase at clocksource init
0064  * @mask:       clocksource mask
0065  * @mult:       clocksource multiplier
0066  * @shift:      clocksource shift
0067  * @basetime[clock_id]: basetime per clock_id
0068  * @offset[clock_id]:   time namespace offset per clock_id
0069  * @tz_minuteswest: minutes west of Greenwich
0070  * @tz_dsttime:     type of DST correction
0071  * @hrtimer_res:    hrtimer resolution
0072  * @__unused:       unused
0073  * @arch_data:      architecture specific data (optional, defaults
0074  *          to an empty struct)
0075  *
0076  * vdso_data will be accessed by 64 bit and compat code at the same time
0077  * so we should be careful before modifying this structure.
0078  *
0079  * @basetime is used to store the base time for the system wide time getter
0080  * VVAR page.
0081  *
0082  * @offset is used by the special time namespace VVAR pages which are
0083  * installed instead of the real VVAR page. These namespace pages must set
0084  * @seq to 1 and @clock_mode to VDSO_CLOCKMODE_TIMENS to force the code into
0085  * the time namespace slow path. The namespace aware functions retrieve the
0086  * real system wide VVAR page, read host time and add the per clock offset.
0087  * For clocks which are not affected by time namespace adjustment the
0088  * offset must be zero.
0089  */
0090 struct vdso_data {
0091     u32         seq;
0092
0093     s32         clock_mode;
0094     u64         cycle_last;
0095     u64         mask;
0096     u32         mult;
0097     u32         shift;
0098
0099     union {
0100         struct vdso_timestamp   basetime[VDSO_BASES];
0101         struct timens_offset    offset[VDSO_BASES];
0102     };
0103
0104     s32         tz_minuteswest;
0105     s32         tz_dsttime;
0106     u32         hrtimer_res;
0107     u32         __unused;
0108
0109     struct arch_vdso_data   arch_data;
0110 };
0111
0112 /*
0113  * We use the hidden visibility to prevent the compiler from generating a GOT
0114  * relocation. Not only is going through a GOT useless (the entry couldn't and
0115  * must not be overridden by another library), it does not even work: the linker
0116  * cannot generate an absolute address to the data page.
0117  *
0118  * With the hidden visibility, the compiler simply generates a PC-relative
0119  * relocation, and this is what we need.
0120  */
0121 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
0122 extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
0123
0124 /*
0125  * The generic vDSO implementation requires that gettimeofday.h
0126  * provides:
0127  * - __arch_get_vdso_data(): to get the vdso datapage.
0128  * - __arch_get_hw_counter(): to get the hw counter based on the
0129  *   clock_mode.
0130  * - gettimeofday_fallback(): fallback for gettimeofday.
0131  * - clock_gettime_fallback(): fallback for clock_gettime.
0132  * - clock_getres_fallback(): fallback for clock_getres.
0133  */
0134 #ifdef ENABLE_COMPAT_VDSO
0135 #include <asm/vdso/compat_gettimeofday.h>
0136 #else
0137 #include <asm/vdso/gettimeofday.h>
0138 #endif /* ENABLE_COMPAT_VDSO */
0139
0140 #endif /* !__ASSEMBLY__ */
0141
0142 #endif /* __VDSO_DATAPAGE_H */