tile: implement gettimeofday() via vDSO

This change creates the framework for vDSO calls, makes the existing
rt_sigreturn() mechanism use it, and adds a fast gettimeofday().
Now that we need to expose the vDSO address to userspace, we add
AT_SYSINFO_EHDR to the set of aux entries provided to userspace.
(You can disable any extra vDSO support by booting with vdso=0,
but the rt_sigreturn vDSO page will still be provided.)

Note that glibc has supported the tile vDSO since release 2.17.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

1 files changed, 36 insertions, 1 deletions

diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c
index 5ac397ec6986..36dc1e1bc0a0 100644
--- a/arch/tile/kernel/time.c
+++ b/arch/tile/kernel/time.c
@@ -23,8 +23,10 @@
 #include <linux/smp.h>
 #include <linux/delay.h>
 #include <linux/module.h>
+#include <linux/timekeeper_internal.h>
 #include <asm/irq_regs.h>
 #include <asm/traps.h>
+#include <asm/vdso.h>
 #include <hv/hypervisor.h>
 #include <arch/interrupts.h>
 #include <arch/spr_def.h>
@@ -110,7 +112,6 @@ void __init time_init(void)
 	setup_tile_timer();
 }
 
-
 /*
  * Define the tile timer clock event device.  The timer is driven by
  * the TILE_TIMER_CONTROL register, which consists of a 31-bit down
@@ -237,3 +238,37 @@ cycles_t ns2cycles(unsigned long nsecs)
 	struct clock_event_device *dev = &__raw_get_cpu_var(tile_timer);
 	return ((u64)nsecs * dev->mult) >> dev->shift;
 }
+
+void update_vsyscall_tz(void)
+{
+	/* Userspace gettimeofday will spin while this value is odd. */
+	++vdso_data->tz_update_count;
+	smp_wmb();
+	vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;
+	vdso_data->tz_dsttime = sys_tz.tz_dsttime;
+	smp_wmb();
+	++vdso_data->tz_update_count;
+}
+
+void update_vsyscall(struct timekeeper *tk)
+{
+	struct timespec wall_time = tk_xtime(tk);
+	struct timespec *wtm = &tk->wall_to_monotonic;
+	struct clocksource *clock = tk->clock;
+
+	if (clock != &cycle_counter_cs)
+		return;
+
+	/* Userspace gettimeofday will spin while this value is odd. */
+	++vdso_data->tb_update_count;
+	smp_wmb();
+	vdso_data->xtime_tod_stamp = clock->cycle_last;
+	vdso_data->xtime_clock_sec = wall_time.tv_sec;
+	vdso_data->xtime_clock_nsec = wall_time.tv_nsec;
+	vdso_data->wtom_clock_sec = wtm->tv_sec;
+	vdso_data->wtom_clock_nsec = wtm->tv_nsec;
+	vdso_data->mult = clock->mult;
+	vdso_data->shift = clock->shift;
+	smp_wmb();
+	++vdso_data->tb_update_count;
+}