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lib/vdso: Provide generic VDSO implementation

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In the last few years the kernel gained quite some architecture specific
vdso implementations which contain very similar code.

Introduce a generic VDSO implementation of gettimeofday() which will be
shareable between architectures once they are converted over.

The implementation is based on the current x86 VDSO code.

[ tglx: Massaged changelog and made the kernel doc tabular ]

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/20190621095252.32307-3-vincenzo.frascino@arm.com
This commit is contained in:
Vincenzo Frascino 2019-06-21 10:52:29 +01:00 • committed by Thomas Gleixner
parent 361f8aee9b
commit 00b26474c2
5 changed files with 343 additions and 0 deletions
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56
include/vdso/helpers.h Normal file
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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __VDSO_HELPERS_H
#define __VDSO_HELPERS_H
#ifndef __ASSEMBLY__
#include <vdso/datapage.h>
static __always_inline u32 vdso_read_begin(const struct vdso_data *vd)
{
u32 seq;
while ((seq = READ_ONCE(vd->seq)) & 1)
cpu_relax();
smp_rmb();
return seq;
}
static __always_inline u32 vdso_read_retry(const struct vdso_data *vd,
u32 start)
{
u32 seq;
smp_rmb();
seq = READ_ONCE(vd->seq);
return seq != start;
}
static __always_inline void vdso_write_begin(struct vdso_data *vd)
{
/*
* WRITE_ONCE it is required otherwise the compiler can validly tear
* updates to vd[x].seq and it is possible that the value seen by the
* reader it is inconsistent.
*/
WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1);
WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1);
smp_wmb();
}
static __always_inline void vdso_write_end(struct vdso_data *vd)
{
smp_wmb();
/*
* WRITE_ONCE it is required otherwise the compiler can validly tear
* updates to vd[x].seq and it is possible that the value seen by the
* reader it is inconsistent.
*/
WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1);
WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1);
}
#endif /* !__ASSEMBLY__ */
#endif /* __VDSO_HELPERS_H */