x86: Introduce asm/vdso/clocksource.h

The vDSO library should only include the necessary headers required for
a userspace library (UAPI and a minimal set of kernel headers). To make
this possible it is necessary to isolate from the kernel headers the
common parts that are strictly necessary to build the library.

Introduce asm/vdso/clocksource.h to contain all the arm64 specific
functions that are suitable for vDSO inclusion.

This header will be required by a future patch that will generalize
vdso/clocksource.h.
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200320145351.32292-5-vincenzo.frascino@arm.com

arch/x86/include/asm/clocksource.h

@@ -4,10 +4,7 @@
 #ifndef _ASM_X86_CLOCKSOURCE_H
 #define _ASM_X86_CLOCKSOURCE_H
 
-#define VDSO_ARCH_CLOCKMODES	\
-	VDSO_CLOCKMODE_TSC,	\
-	VDSO_CLOCKMODE_PVCLOCK,	\
-	VDSO_CLOCKMODE_HVCLOCK
+#include <asm/vdso/clocksource.h>
 
 extern unsigned int vclocks_used;
 

arch/x86/include/asm/vdso/clocksource.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_VDSO_CLOCKSOURCE_H
+#define __ASM_VDSO_CLOCKSOURCE_H
+
+#define VDSO_ARCH_CLOCKMODES	\
+	VDSO_CLOCKMODE_TSC,	\
+	VDSO_CLOCKMODE_PVCLOCK,	\
+	VDSO_CLOCKMODE_HVCLOCK
+
+#endif /* __ASM_VDSO_CLOCKSOURCE_H */