nds32: VDSO support

This patch adds VDSO support. The VDSO code is currently used for
sys_rt_sigreturn() and optimised gettimeofday() (using the SoC timer counter).

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

arch/nds32/include/asm/vdso.h

@@ -0,0 +1,24 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0
+ * Copyright (C) 2005-2017 Andes Technology Corporation
+ */
+
+#ifndef __ASM_VDSO_H
+#define __ASM_VDSO_H
+
+#ifdef __KERNEL__
+
+#ifndef __ASSEMBLY__
+
+#include <generated/vdso-offsets.h>
+
+#define VDSO_SYMBOL(base, name)						   \
+({									   \
+	(unsigned long)(vdso_offset_##name + (unsigned long)(base)); \
+})
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __KERNEL__ */
+
+#endif /* __ASM_VDSO_H */

arch/nds32/include/asm/vdso_datapage.h

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2012 ARM Limited
+// Copyright (C) 2005-2017 Andes Technology Corporation
+#ifndef __ASM_VDSO_DATAPAGE_H
+#define __ASM_VDSO_DATAPAGE_H
+
+#ifdef __KERNEL__
+
+#ifndef __ASSEMBLY__
+
+struct vdso_data {
+	bool cycle_count_down;	/* timer cyclye counter is decrease with time */
+	u32 cycle_count_offset;	/* offset of timer cycle counter register */
+	u32 seq_count;		/* sequence count - odd during updates */
+	u32 xtime_coarse_sec;	/* coarse time */
+	u32 xtime_coarse_nsec;
+
+	u32 wtm_clock_sec;	/* wall to monotonic offset */
+	u32 wtm_clock_nsec;
+	u32 xtime_clock_sec;	/* CLOCK_REALTIME - seconds */
+	u32 cs_mult;		/* clocksource multiplier */
+	u32 cs_shift;		/* Cycle to nanosecond divisor (power of two) */
+
+	u64 cs_cycle_last;	/* last cycle value */
+	u64 cs_mask;		/* clocksource mask */
+
+	u64 xtime_clock_nsec;	/* CLOCK_REALTIME sub-ns base */
+	u32 tz_minuteswest;	/* timezone info for gettimeofday(2) */
+	u32 tz_dsttime;
+};
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __KERNEL__ */
+
+#endif /* __ASM_VDSO_DATAPAGE_H */

arch/nds32/include/asm/vdso_timer_info.h

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+extern struct timer_info_t timer_info;
+#define EMPTY_VALUE ~(0UL)
+#define EMPTY_TIMER_MAPPING EMPTY_VALUE
+#define EMPTY_REG_OFFSET EMPTY_VALUE
+
+struct timer_info_t
+{
+	bool cycle_count_down;
+	unsigned long mapping_base;
+	unsigned long cycle_count_reg_offset;
+};