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 #define VCLOCK_TIMENS UINT_MAX 25 26 /** 27 * struct vdso_timestamp - basetime per clock_id 28 * @sec: seconds 29 * @nsec: nanoseconds 30 * 31 * There is one vdso_timestamp object in vvar for each vDSO-accelerated 32 * clock_id. For high-resolution clocks, this encodes the time 33 * corresponding to vdso_data.cycle_last. For coarse clocks this encodes 34 * the actual time. 35 * 36 * To be noticed that for highres clocks nsec is left-shifted by 37 * vdso_data.cs[x].shift. 38 */ 39 struct vdso_timestamp { 40 u64 sec; 41 u64 nsec; 42 }; 43 44 /** 45 * struct vdso_data - vdso datapage representation 46 * @seq: timebase sequence counter 47 * @clock_mode: clock mode 48 * @cycle_last: timebase at clocksource init 49 * @mask: clocksource mask 50 * @mult: clocksource multiplier 51 * @shift: clocksource shift 52 * @basetime[clock_id]: basetime per clock_id 53 * @offset[clock_id]: time namespace offset per clock_id 54 * @tz_minuteswest: minutes west of Greenwich 55 * @tz_dsttime: type of DST correction 56 * @hrtimer_res: hrtimer resolution 57 * @__unused: unused 58 * 59 * vdso_data will be accessed by 64 bit and compat code at the same time 60 * so we should be careful before modifying this structure. 61 * 62 * @basetime is used to store the base time for the system wide time getter 63 * VVAR page. 64 * 65 * @offset is used by the special time namespace VVAR pages which are 66 * installed instead of the real VVAR page. These namespace pages must set 67 * @seq to 1 and @clock_mode to VLOCK_TIMENS to force the code into the 68 * time namespace slow path. The namespace aware functions retrieve the 69 * real system wide VVAR page, read host time and add the per clock offset. 70 * For clocks which are not affected by time namespace adjustment the 71 * offset must be zero. 72 */ 73 struct vdso_data { 74 u32 seq; 75 76 s32 clock_mode; 77 u64 cycle_last; 78 u64 mask; 79 u32 mult; 80 u32 shift; 81 82 union { 83 struct vdso_timestamp basetime[VDSO_BASES]; 84 struct timens_offset offset[VDSO_BASES]; 85 }; 86 87 s32 tz_minuteswest; 88 s32 tz_dsttime; 89 u32 hrtimer_res; 90 u32 __unused; 91 }; 92 93 /* 94 * We use the hidden visibility to prevent the compiler from generating a GOT 95 * relocation. Not only is going through a GOT useless (the entry couldn't and 96 * must not be overridden by another library), it does not even work: the linker 97 * cannot generate an absolute address to the data page. 98 * 99 * With the hidden visibility, the compiler simply generates a PC-relative 100 * relocation, and this is what we need. 101 */ 102 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden"))); 103 104 #endif /* !__ASSEMBLY__ */ 105 106 #endif /* __VDSO_DATAPAGE_H */ 107