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: Mark Salyzyn <salyzyn@android.com>
Bug: 63737556
Bug: 20045882
Change-Id: I0bb3c6bafe57f9ed69350e2dd54edaae58316e8f

diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index e50a72ca08f12e6568c41906cd8466233e32ffe5..bb241d4afea76a4877da5c0fec8e733f31717aa0 100644 (file)
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -172,6 +172,7 @@ 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 */
        }
 }
 

diff --git a/arch/arm/vdso/vdso.lds.S b/arch/arm/vdso/vdso.lds.S
index 1d81e8c3acf6bb9a00a5a578a262ba720bb861ca..1eb577091d1f85e6f11cc327bffbc42e4b409474 100644 (file)
--- a/arch/arm/vdso/vdso.lds.S
+++ b/arch/arm/vdso/vdso.lds.S
@@ -83,6 +83,7 @@ VERSION
                __vdso_clock_gettime;
                __vdso_gettimeofday;
                __vdso_clock_getres;
+               __vdso_time;
        local: *;
        };
 }

diff --git a/arch/arm64/kernel/vdso/compiler.h b/arch/arm64/kernel/vdso/compiler.h
new file mode 100644 (file)
index 0000000..fb27545
--- /dev/null
+++ b/arch/arm64/kernel/vdso/compiler.h
@@ -0,0 +1,70 @@
+/*
+ * 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 */

diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index beca249bc2f394ca3592a76d868b60ff275ddb5b..9de0ffc369c51b9391ead487ee1efb331e8aa9a0 100644 (file)
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -88,6 +88,7 @@ VERSION
                __kernel_gettimeofday;
                __kernel_clock_gettime;
                __kernel_clock_getres;
+               __kernel_time;
        local: *;
        };
 }

diff --git a/lib/vdso/vgettimeofday.c b/lib/vdso/vgettimeofday.c
index 075a1171944d7966e3ba4a6515a7daec8673bb79..00d93df8045f7945cc20ca956ec06b0a45d761a9 100644 (file)
--- a/lib/vdso/vgettimeofday.c
+++ b/lib/vdso/vgettimeofday.c
@@ -385,3 +385,13 @@ 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;
+}