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 * @offset[clock_id]: time namespace offset per clock_id 52 * @tz_minuteswest: minutes west of Greenwich 53 * @tz_dsttime: type of DST correction 54 * @hrtimer_res: hrtimer resolution 55 * @__unused: unused 56 * 57 * vdso_data will be accessed by 64 bit and compat code at the same time 58 * so we should be careful before modifying this structure. 59 * 60 * @basetime is used to store the base time for the system wide time getter 61 * VVAR page. 62 * 63 * @offset is used by the special time namespace VVAR pages which are 64 * installed instead of the real VVAR page. These namespace pages must set 65 * @seq to 1 and @clock_mode to VLOCK_TIMENS to force the code into the 66 * time namespace slow path. The namespace aware functions retrieve the 67 * real system wide VVAR page, read host time and add the per clock offset. 68 * For clocks which are not affected by time namespace adjustment the 69 * offset must be zero. 70 */ 71 struct vdso_data { 72 u32 seq; 73 74 s32 clock_mode; 75 u64 cycle_last; 76 u64 mask; 77 u32 mult; 78 u32 shift; 79 80 union { 81 struct vdso_timestamp basetime[VDSO_BASES]; 82 struct timens_offset offset[VDSO_BASES]; 83 }; 84 85 s32 tz_minuteswest; 86 s32 tz_dsttime; 87 u32 hrtimer_res; 88 u32 __unused; 89 }; 90 91 /* 92 * We use the hidden visibility to prevent the compiler from generating a GOT 93 * relocation. Not only is going through a GOT useless (the entry couldn't and 94 * must not be overridden by another library), it does not even work: the linker 95 * cannot generate an absolute address to the data page. 96 * 97 * With the hidden visibility, the compiler simply generates a PC-relative 98 * relocation, and this is what we need. 99 */ 100 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden"))); 101 102 #endif /* !__ASSEMBLY__ */ 103 104 #endif /* __VDSO_DATAPAGE_H */ 105