linux/include/vdso/datapage.h
Sven Schnelle d60d7de3e1 lib/vdso: Allow to add architecture-specific vdso data
The initial assumption that all VDSO related data can be completely generic
does not hold. S390 needs architecture specific storage to access the clock
steering information.

Add struct arch_vdso_data to the vdso data struct. For architectures which
do not need extra data this defaults to an empty struct. Architectures
which require it, enable CONFIG_ARCH_HAS_VDSO_DATA and provide their
specific struct in asm/vdso/data.h.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200804150124.41692-2-svens@linux.ibm.com
2020-08-06 10:57:30 +02:00

143 lines
4.1 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __VDSO_DATAPAGE_H
#define __VDSO_DATAPAGE_H
#ifndef __ASSEMBLY__
#include <linux/compiler.h>
#include <uapi/linux/time.h>
#include <uapi/linux/types.h>
#include <uapi/asm-generic/errno-base.h>
#include <vdso/bits.h>
#include <vdso/clocksource.h>
#include <vdso/ktime.h>
#include <vdso/limits.h>
#include <vdso/math64.h>
#include <vdso/processor.h>
#include <vdso/time.h>
#include <vdso/time32.h>
#include <vdso/time64.h>
#ifdef CONFIG_ARCH_HAS_VDSO_DATA
#include <asm/vdso/data.h>
#else
struct arch_vdso_data {};
#endif
#define VDSO_BASES (CLOCK_TAI + 1)
#define VDSO_HRES (BIT(CLOCK_REALTIME) | \
BIT(CLOCK_MONOTONIC) | \
BIT(CLOCK_BOOTTIME) | \
BIT(CLOCK_TAI))
#define VDSO_COARSE (BIT(CLOCK_REALTIME_COARSE) | \
BIT(CLOCK_MONOTONIC_COARSE))
#define VDSO_RAW (BIT(CLOCK_MONOTONIC_RAW))
#define CS_HRES_COARSE 0
#define CS_RAW 1
#define CS_BASES (CS_RAW + 1)
/**
* struct vdso_timestamp - basetime per clock_id
* @sec: seconds
* @nsec: nanoseconds
*
* There is one vdso_timestamp object in vvar for each vDSO-accelerated
* clock_id. For high-resolution clocks, this encodes the time
* corresponding to vdso_data.cycle_last. For coarse clocks this encodes
* the actual time.
*
* To be noticed that for highres clocks nsec is left-shifted by
* vdso_data.cs[x].shift.
*/
struct vdso_timestamp {
u64 sec;
u64 nsec;
};
/**
* struct vdso_data - vdso datapage representation
* @seq: timebase sequence counter
* @clock_mode: clock mode
* @cycle_last: timebase at clocksource init
* @mask: clocksource mask
* @mult: clocksource multiplier
* @shift: clocksource shift
* @basetime[clock_id]: basetime per clock_id
* @offset[clock_id]: time namespace offset per clock_id
* @tz_minuteswest: minutes west of Greenwich
* @tz_dsttime: type of DST correction
* @hrtimer_res: hrtimer resolution
* @__unused: unused
* @arch_data: architecture specific data (optional, defaults
* to an empty struct)
*
* vdso_data will be accessed by 64 bit and compat code at the same time
* so we should be careful before modifying this structure.
*
* @basetime is used to store the base time for the system wide time getter
* VVAR page.
*
* @offset is used by the special time namespace VVAR pages which are
* installed instead of the real VVAR page. These namespace pages must set
* @seq to 1 and @clock_mode to VDSO_CLOCKMODE_TIMENS to force the code into
* the time namespace slow path. The namespace aware functions retrieve the
* real system wide VVAR page, read host time and add the per clock offset.
* For clocks which are not affected by time namespace adjustment the
* offset must be zero.
*/
struct vdso_data {
u32 seq;
s32 clock_mode;
u64 cycle_last;
u64 mask;
u32 mult;
u32 shift;
union {
struct vdso_timestamp basetime[VDSO_BASES];
struct timens_offset offset[VDSO_BASES];
};
s32 tz_minuteswest;
s32 tz_dsttime;
u32 hrtimer_res;
u32 __unused;
struct arch_vdso_data arch_data;
};
/*
* We use the hidden visibility to prevent the compiler from generating a GOT
* relocation. Not only is going through a GOT useless (the entry couldn't and
* must not be overridden by another library), it does not even work: the linker
* cannot generate an absolute address to the data page.
*
* With the hidden visibility, the compiler simply generates a PC-relative
* relocation, and this is what we need.
*/
extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
/*
* The generic vDSO implementation requires that gettimeofday.h
* provides:
* - __arch_get_vdso_data(): to get the vdso datapage.
* - __arch_get_hw_counter(): to get the hw counter based on the
* clock_mode.
* - gettimeofday_fallback(): fallback for gettimeofday.
* - clock_gettime_fallback(): fallback for clock_gettime.
* - clock_getres_fallback(): fallback for clock_getres.
*/
#ifdef ENABLE_COMPAT_VDSO
#include <asm/vdso/compat_gettimeofday.h>
#else
#include <asm/vdso/gettimeofday.h>
#endif /* ENABLE_COMPAT_VDSO */
#endif /* !__ASSEMBLY__ */
#endif /* __VDSO_DATAPAGE_H */