kernel: gtod: vsyscall
Introduce kernel user helper vsyscall to allow a higher performance
gettimeofday implementation in user-space.
Change-Id: I9b9971d217382129170ecd6a35461539dac9eebb
Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 56691a5..07d599b 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -272,6 +272,13 @@
If unsure, say N
+config GENERIC_TIME_VSYSCALL
+ bool "Enable gettimeofday updates"
+ depends on CPU_V7
+ help
+ Enables updating the kernel user helper area with the xtime struct
+ data for gettimeofday via kernel user helpers.
+
source "init/Kconfig"
source "kernel/Kconfig.freezer"
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 22b0f1e..cd1e2a0 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -63,6 +63,7 @@
obj-$(CONFIG_SWP_EMULATE) += swp_emulate.o
CFLAGS_swp_emulate.o := -Wa,-march=armv7-a
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
+obj-$(CONFIG_GENERIC_TIME_VSYSCALL) += update_vsyscall_arm.o
obj-$(CONFIG_CPU_XSCALE) += xscale-cp0.o
obj-$(CONFIG_CPU_XSC3) += xscale-cp0.o
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 7a8c2d6..ddd421c 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -764,6 +764,97 @@
.align 5
.globl __kuser_helper_start
__kuser_helper_start:
+#ifdef GENERIC_TIME_VSYSCALL
+/*
+ * Reference declaration:
+ *
+ * extern struct timezone __kernel_helper_gtod_timezone
+ * extern unsigned int __kernel_helper_gtod_seqnum
+ *
+ * Definition and user space usage example:
+ *
+ * #define __kernel_helper_gtod_timezone (*(unsigned int*)0xffff0f20)
+ * #define __kernel_helper_gtod_seqnum (*(unsigned int*)0xffff0f28)
+ *
+ * unsigned int prelock, postlock ;
+ * do {
+ * prelock = __kernel_helper_gtod_seqnum;
+ * memcpy(&tz, (void*)&(__kernel_helper_gtod_timezone),
+ * sizeof(struct timezone)) ;
+ * postlock = __kernel_helper_gtod_seqnum;
+ * } while (prelock != postlock);
+ *
+ * 0xffff0f20-3: tz_minuteswest
+ * 0xffff0f24-7: tz_dsttime
+ * 0xffff0f28-b: sequence #.
+ * 0xffff0f30-3: offset into CONFIG_USER_ACCESSIBLE_TIMER_BASE to get the timer.
+ * 0xffff0f34-7: Feature flag
+ * 0xffff0f38-b: wall-to-mononic: tv_sec
+ * 0xffff0f3c-f: wall-to-mononic: tv_nsec
+ */
+ .globl __kuser_gtod_timezone
+__kuser_gtod_timezone: @0xffff0f20
+ .word 0
+ .word 0
+ .word 0
+ .word 0
+ .word 0
+ /* This offset is where the flag to enable the
+ * user accessible timers is located.
+ */
+ .word 0
+ .word 0
+ .word 0
+ .align 5
+
+/*
+ * Reference declaration:
+ *
+ * extern struct timeval __kernel_helper_gtod_timeval
+ * extern unsigned int __kernel_helper_gtod_seqnum
+ *
+ * Definition and user space usage example:
+ *
+ * #define __kernel_helper_gtod_timeval (*(unsigned int*)0xffff0f40)
+ * #define __kernel_helper_gtod_seqnum (*(unsigned int*)0xffff0f48)
+ *
+ * unsigned int prelock, postlock ;
+ * struct gtod {
+ * uint64_t cycle_last;
+ * uint64_t mask;
+ * uint32_t mult;
+ * uint32_t shift;
+ * uint32_t tv_sec;
+ * uint32_t tv_nsec;
+ * };
+ * struct gtod gdtod;
+ *
+ * do {
+ * prelock = __kernel_helper_gtod_seqnum;
+ * memcpy(&gdtod, (void*)&(__kernel_helper_gtod_timeval),
+ * sizeof(struct gtod)) ;
+ * postlock = __kernel_helper_gtod_seqnum;
+ * } while (prelock != postlock);
+ *
+ * 0xffff0f40-7: cycle_last
+ * 0xffff0f48-f: mask
+ * 0xffff0f50-3: mult
+ * 0xffff0f54-7: shift
+ * 0xffff0f58-b: tv_sec
+ * 0xffff0f5c-f: tv_nsec
+ */
+ .globl __kuser_gtod_timeval
+__kuser_gtod_timeval: @0xffff0f40
+ .word 0
+ .word 0
+ .word 0
+ .word 0
+ .word 0
+ .word 0
+ .word 0
+ .word 0
+ .align 5
+#endif
/*
* Due to the length of some sequences, __kuser_cmpxchg64 spans 2 regular
diff --git a/arch/arm/kernel/update_vsyscall_arm.c b/arch/arm/kernel/update_vsyscall_arm.c
new file mode 100644
index 0000000..51f47ae
--- /dev/null
+++ b/arch/arm/kernel/update_vsyscall_arm.c
@@ -0,0 +1,100 @@
+/* Copyright (c) 2012, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only 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.
+ */
+
+#include <linux/export.h>
+#include <linux/clocksource.h>
+#include <linux/time.h>
+#include "update_vsyscall_arm.h"
+/*
+ * See entry-armv.S for the offsets into the kernel user helper for
+ * these fields.
+ */
+#define ARM_VSYSCALL_TIMER_TZ 0xf20
+#define ARM_VSYSCALL_TIMER_SEQ 0xf28
+#define ARM_VSYSCALL_TIMER_OFFSET 0xf30
+#define ARM_VSYSCALL_TIMER_WTM_TV_SEC 0xf38
+#define ARM_VSYSCALL_TIMER_WTM_TV_NSEC 0xf3c
+#define ARM_VSYSCALL_TIMER_CYCLE_LAST 0xf40
+#define ARM_VSYSCALL_TIMER_MASK 0xf48
+#define ARM_VSYSCALL_TIMER_MULT 0xf50
+#define ARM_VSYSCALL_TIMER_SHIFT 0xf54
+#define ARM_VSYSCALL_TIMER_TV_SEC 0xf58
+#define ARM_VSYSCALL_TIMER_TV_NSEC 0xf5c
+
+struct kernel_gtod_t {
+ u64 cycle_last;
+ u64 mask;
+ u32 mult;
+ u32 shift;
+ u32 tv_sec;
+ u32 tv_nsec;
+};
+
+struct kernel_tz_t {
+ u32 tz_minuteswest;
+ u32 tz_dsttime;
+};
+
+struct kernel_wtm_t {
+ u32 tv_sec;
+ u32 tv_nsec;
+};
+
+/*
+ * Updates the kernel user helper area with the current timespec
+ * data, as well as additional fields needed to calculate
+ * gettimeofday, clock_gettime, etc.
+ */
+void
+update_vsyscall(struct timespec *ts, struct timespec *wtm,
+ struct clocksource *c, u32 mult)
+{
+ unsigned long vectors = (unsigned long)vectors_page;
+ unsigned long flags;
+ unsigned *seqnum = (unsigned *)(vectors + ARM_VSYSCALL_TIMER_SEQ);
+ struct kernel_gtod_t *dgtod = (struct kernel_gtod_t *)(vectors +
+ ARM_VSYSCALL_TIMER_CYCLE_LAST);
+ struct kernel_wtm_t *dgwtm = (struct kernel_wtm_t *)(vectors +
+ ARM_VSYSCALL_TIMER_WTM_TV_SEC);
+
+ write_seqlock_irqsave(&kuh_time_lock, flags);
+ *seqnum = kuh_time_lock.sequence;
+ dgtod->cycle_last = c->cycle_last;
+ dgtod->mask = c->mask;
+ dgtod->mult = c->mult;
+ dgtod->shift = c->shift;
+ dgtod->tv_sec = ts->tv_sec;
+ dgtod->tv_nsec = ts->tv_nsec;
+ dgwtm->tv_sec = wtm->tv_sec;
+ dgwtm->tv_nsec = wtm->tv_nsec;
+ *seqnum = kuh_time_lock.sequence + 1;
+ write_sequnlock_irqrestore(&kuh_time_lock, flags);
+}
+EXPORT_SYMBOL(update_vsyscall);
+
+void
+update_vsyscall_tz(void)
+{
+ unsigned long vectors = (unsigned long)vectors_page;
+ unsigned long flags;
+ unsigned *seqnum = (unsigned *)(vectors + ARM_VSYSCALL_TIMER_SEQ);
+ struct kernel_tz_t *dgtod = (struct kernel_tz_t *)(vectors +
+ ARM_VSYSCALL_TIMER_TZ);
+
+ write_seqlock_irqsave(&kuh_time_lock, flags);
+ *seqnum = kuh_time_lock.sequence;
+ dgtod->tz_minuteswest = sys_tz.tz_minuteswest;
+ dgtod->tz_dsttime = sys_tz.tz_dsttime;
+ *seqnum = kuh_time_lock.sequence + 1;
+ write_sequnlock_irqrestore(&kuh_time_lock, flags);
+}
+EXPORT_SYMBOL(update_vsyscall_tz);
diff --git a/arch/arm/kernel/update_vsyscall_arm.h b/arch/arm/kernel/update_vsyscall_arm.h
new file mode 100644
index 0000000..d06ca56
--- /dev/null
+++ b/arch/arm/kernel/update_vsyscall_arm.h
@@ -0,0 +1,23 @@
+/* Copyright (c) 2012, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only 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.
+ */
+#include <linux/export.h>
+#include <linux/clocksource.h>
+#include <linux/time.h>
+
+extern void *vectors_page;
+extern struct timezone sys_tz;
+
+/*
+ * This read-write spinlock protects us from races in SMP while
+ * updating the kernel user helper-embedded time.
+ */
+__cacheline_aligned_in_smp DEFINE_SEQLOCK(kuh_time_lock);