vdso/ARM: Make union vdso_data_store available for all architectures

The vDSO data page "union vdso_data_store" is defined in an ARM specific
header file and also defined in several other places.

Move the definition from the ARM header file into the generic vdso datapage
header to make it also usable for others and to prevent code duplication.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240219153939.75719-5-anna-maria@linutronix.de

arch/arm/include/asm/elf.h

@@ -4,7 +4,6 @@
 
 #include <asm/auxvec.h>
 #include <asm/hwcap.h>
-#include <asm/vdso_datapage.h>
 
 /*
  * ELF register definitions..

arch/arm/kernel/asm-offsets.c

@@ -21,10 +21,12 @@
 #include <asm/mpu.h>
 #include <asm/procinfo.h>
 #include <asm/suspend.h>
-#include <asm/vdso_datapage.h>
 #include <asm/hardware/cache-l2x0.h>
 #include <linux/kbuild.h>
 #include <linux/arm-smccc.h>
+
+#include <vdso/datapage.h>
+
 #include "signal.h"
 
 /*

arch/arm/kernel/vdso.c

@@ -21,7 +21,6 @@
 #include <asm/cacheflush.h>
 #include <asm/page.h>
 #include <asm/vdso.h>
-#include <asm/vdso_datapage.h>
 #include <clocksource/arm_arch_timer.h>
 #include <vdso/helpers.h>
 #include <vdso/vsyscall.h>
@@ -35,9 +34,6 @@ extern char vdso_start[], vdso_end[];
 /* Total number of pages needed for the data and text portions of the VDSO. */
 unsigned int vdso_total_pages __ro_after_init;
 
-/*
- * The VDSO data page.
- */
 static union vdso_data_store vdso_data_store __page_aligned_data;
 struct vdso_data *vdso_data = vdso_data_store.data;
 

include/vdso/datapage.h

@@ -19,6 +19,8 @@
 #include <vdso/time32.h>
 #include <vdso/time64.h>
 
+#include <asm/page.h>
+
 #ifdef CONFIG_ARCH_HAS_VDSO_DATA
 #include <asm/vdso/data.h>
 #else
@@ -121,6 +123,14 @@ struct vdso_data {
 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
 extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
 
+/**
+ * union vdso_data_store - Generic vDSO data page
+ */
+union vdso_data_store {
+	struct vdso_data	data[CS_BASES];
+	u8			page[PAGE_SIZE];
+};
+
 /*
  * The generic vDSO implementation requires that gettimeofday.h
  * provides: