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, 49 insertions, 0 deletions

diff --git a/arch/tile/include/asm/vdso.h b/arch/tile/include/asm/vdso.h
new file mode 100644
index 000000000000..9f6a78d665fa
--- /dev/null
+++ b/arch/tile/include/asm/vdso.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2012 Tilera Corporation. 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
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   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, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+
+#ifndef __TILE_VDSO_H__
+#define __TILE_VDSO_H__
+
+#include <linux/types.h>
+
+/*
+ * Note about the vdso_data structure:
+ *
+ * NEVER USE THEM IN USERSPACE CODE DIRECTLY. The layout of the
+ * structure is supposed to be known only to the function in the vdso
+ * itself and may change without notice.
+ */
+
+struct vdso_data {
+	__u64 tz_update_count;  /* Timezone atomicity ctr             */
+	__u64 tb_update_count;  /* Timebase atomicity ctr             */
+	__u64 xtime_tod_stamp;  /* TOD clock for xtime                */
+	__u64 xtime_clock_sec;  /* Kernel time second                 */
+	__u64 xtime_clock_nsec; /* Kernel time nanosecond             */
+	__u64 wtom_clock_sec;   /* Wall to monotonic clock second     */
+	__u64 wtom_clock_nsec;  /* Wall to monotonic clock nanosecond */
+	__u32 mult;             /* Cycle to nanosecond multiplier     */
+	__u32 shift;            /* Cycle to nanosecond divisor (power of two) */
+	__u32 tz_minuteswest;   /* Minutes west of Greenwich          */
+	__u32 tz_dsttime;       /* Type of dst correction             */
+};
+
+extern struct vdso_data *vdso_data;
+
+/* __vdso_rt_sigreturn is defined with the addresses in the vdso page. */
+extern void __vdso_rt_sigreturn(void);
+
+extern int setup_vdso_pages(void);
+
+#endif /* __TILE_VDSO_H__ */