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FROMLIST: lib: vdso: add support for time

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(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: Mark Salyzyn <salyzyn@android.com>
Bug: 63737556
Bug: 20045882
Change-Id: I0bb3c6bafe57f9ed69350e2dd54edaae58316e8f
Signed-off-by: khusika <khusikadhamar@gmail.com>
Signed-off-by: azrim <mirzaspc@gmail.com>
This commit is contained in:
Mark Salyzyn 2017-10-27 08:58:18 -07:00 committed by azrim
parent 0038a5bd2d
commit 973725e4a5
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GPG Key ID: 497F8FB059B45D1C
5 changed files with 14 additions and 0 deletions
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1
arch/arm/kernel/vdso.c
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@ -194,6 +194,7 @@ static void __init patch_vdso(void *ehdr)
vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
vdso_nullpatch_one(&einfo, "__vdso_clock_getres");
/* do not zero out __vdso_time, no cntvct_ok dependency */
}
}

1
arch/arm/vdso/vdso.lds.S
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@ -83,6 +83,7 @@ VERSION
__vdso_clock_gettime;
__vdso_gettimeofday;
__vdso_clock_getres;
__vdso_time;
local: *;
};
}

1
arch/arm64/kernel/vdso/compiler.h
View File

@ -65,5 +65,6 @@ static __always_inline notrace u64 arch_vdso_read_counter(void)
#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 */

1
arch/arm64/kernel/vdso/vdso.lds.S
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@ -94,6 +94,7 @@ VERSION
__kernel_gettimeofday;
__kernel_clock_gettime;
__kernel_clock_getres;
__kernel_time;
local: *;
};
}

10
lib/vdso/vgettimeofday.c
View File

@ -386,3 +386,13 @@ int __vdso_clock_getres(clockid_t clock, struct timespec *res)
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;
}