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Unverified Commit 8e7670e2 authored by Mark Salyzyn's avatar Mark Salyzyn Committed by derfelot
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FROMLIST: lib: vdso: add support for time 

(cherry pick from url https://patchwork.kernel.org/patch/10053549/

)

Add time() vdso support to match up with existing support in the x86's
vdso.  Currently benefitting arm and arm64 which uses the common
vgettimeofday.c implementation.  On arm provides about a ~14 fold
improvement in speed over the straight syscall, and about a ~5 fold
improvement in speed over an alternate library implementation that
relies on the vdso call to gettimeofday to fulfill the request.

We can provide __vdso_time even if we can not provide a speed
enhanced __vdso_gettimeofday.

Signed-off-by: default avatarMark Salyzyn <salyzyn@android.com>
Bug: 63737556
Bug: 20045882
Change-Id: I0bb3c6bafe57f9ed69350e2dd54edaae58316e8f
parent 85ba8598

arch/arm/kernel/vdso.c

+1 −0
Original line number Original line Diff line number Diff line
@@ -174,6 +174,7 @@ static void __init patch_vdso(void *ehdr) 
		vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");

		vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");

		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");

		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");

		vdso_nullpatch_one(&einfo, "__vdso_clock_getres");

		vdso_nullpatch_one(&einfo, "__vdso_clock_getres");

		/* do not zero out __vdso_time, no cntvct_ok dependency */

	}

	}

}

}

arch/arm/vdso/vdso.lds.S

+1 −0
Original line number Original line Diff line number Diff line
@@ -83,6 +83,7 @@ VERSION 
		__vdso_clock_gettime;

		__vdso_clock_gettime;

		__vdso_gettimeofday;

		__vdso_gettimeofday;

		__vdso_clock_getres;

		__vdso_clock_getres;

		__vdso_time;

	local: *;

	local: *;

	};

	};

}
 
}

arch/arm64/kernel/vdso/compiler.h

0 → 100644
+70 −0
Original line number Original line Diff line number Diff line 
/*

 * Userspace implementations of fallback calls

 *

 * Copyright (C) 2017 Cavium, Inc.

 * Copyright (C) 2012 ARM Limited

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 *

 * Author: Will Deacon <will.deacon@arm.com>

 * Rewriten into C by: Andrew Pinski <apinski@cavium.com>

 */



#ifndef __VDSO_COMPILER_H

#define __VDSO_COMPILER_H



#include <asm/processor.h>	/* for cpu_relax()			*/

#include <asm/sysreg.h>		/* for read_sysreg()			*/

#include <asm/unistd.h>

#include <linux/compiler.h>

#include <linux/hrtimer.h>	/* for LOW_RES_NSEC and MONOTONIC_RES_NSEC */



#ifdef CONFIG_ARM_ARCH_TIMER

#define ARCH_PROVIDES_TIMER

#endif



#define DEFINE_FALLBACK(name, type_arg1, name_arg1, type_arg2, name_arg2) \

static notrace long name##_fallback(type_arg1 _##name_arg1,		  \

				    type_arg2 _##name_arg2)		  \

{									  \

	register type_arg1 name_arg1 asm("x0") = _##name_arg1;		  \

	register type_arg2 name_arg2 asm("x1") = _##name_arg2;		  \

	register long ret asm ("x0");					  \

	register long nr asm("x8") = __NR_##name;			  \

									  \

	asm volatile(							  \

	"	svc #0\n"						  \

	: "=r" (ret)							  \

	: "r" (name_arg1), "r" (name_arg2), "r" (nr)			  \

	: "memory");							  \

									  \

	return ret;							  \

}



/*

 * AArch64 implementation of arch_counter_get_cntvct() suitable for vdso

 */

static __always_inline notrace u64 arch_vdso_read_counter(void)

{

	/* Read the virtual counter. */

	isb();

	return read_sysreg(cntvct_el0);

}



/* Rename exported vdso functions */

#define __vdso_clock_gettime __kernel_clock_gettime

#define __vdso_gettimeofday __kernel_gettimeofday

#define __vdso_clock_getres __kernel_clock_getres

#define __vdso_time __kernel_time



#endif /* __VDSO_COMPILER_H */

arch/arm64/kernel/vdso/vdso.lds.S

+1 −0
Original line number Original line Diff line number Diff line
@@ -88,6 +88,7 @@ VERSION 
		__kernel_gettimeofday;

		__kernel_gettimeofday;

		__kernel_clock_gettime;

		__kernel_clock_gettime;

		__kernel_clock_getres;

		__kernel_clock_getres;

		__kernel_time;

	local: *;

	local: *;

	};

	};

}

}

lib/vdso/vgettimeofday.c

+10 −0
Original line number Original line Diff line number Diff line
@@ -385,3 +385,13 @@ int __vdso_clock_getres(clockid_t clock, struct timespec *res) 




	return 0;

	return 0;

}

}



notrace time_t __vdso_time(time_t *t)

{

	const struct vdso_data *vd = __get_datapage();

	time_t result = READ_ONCE(vd->xtime_coarse_sec);



	if (t)

		*t = result;

	return result;

}