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vdso: Define standardized vdso_datapage 

Define a common formet for the vdso datapage as a preparation for sharing
the VDSO implementation as a generic library.

The datastructures are based on the current x86 layout.

[ tglx: Massaged changelog ]

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Shijith Thotton <sthotton@marvell.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Huw Davies <huw@codeweavers.com>
Link: https://lkml.kernel.org/r/20190621095252.32307-2-vincenzo.frascino@arm.com
This commit is contained in:
Vincenzo Frascino 2019-06-21 10:52:28 +01:00 committed by Thomas Gleixner
parent 32e29396f0
commit 361f8aee9b
1 changed files with 93 additions and 0 deletions
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93
include/vdso/datapage.h Normal file
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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __VDSO_DATAPAGE_H
#define __VDSO_DATAPAGE_H
#ifdef __KERNEL__
#ifndef __ASSEMBLY__
#include <linux/bits.h>
#include <linux/time.h>
#include <linux/types.h>
#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
* @tz_minuteswest: minutes west of Greenwich
* @tz_dsttime: type of DST correction
* @hrtimer_res: hrtimer resolution
* @__unused: unused
*
* vdso_data will be accessed by 64 bit and compat code at the same time
* so we should be careful before modifying this structure.
*/
struct vdso_data {
u32 seq;
s32 clock_mode;
u64 cycle_last;
u64 mask;
u32 mult;
u32 shift;
struct vdso_timestamp basetime[VDSO_BASES];
s32 tz_minuteswest;
s32 tz_dsttime;
u32 hrtimer_res;
u32 __unused;
};
/*
* 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")));
#endif /* !__ASSEMBLY__ */
#endif /* __KERNEL__ */
#endif /* __VDSO_DATAPAGE_H */