vdso/vsyscall: Split up __arch_update_vsyscall() into __arch_update_vdso_clock()

The upcoming auxiliary clocks need this hook, too.
To separate the architecture hooks from the timekeeper internals, refactor
the hook to only operate on a single vDSO clock.

While at it, use a more robust #define for the hook override.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250701-vdso-auxclock-v1-3-df7d9f87b9b8@linutronix.de

Author: t-8ch

arch/arm64/include/asm/vdso/vsyscall.h

@@ -13,12 +13,11 @@
  * Update the vDSO data page to keep in sync with kernel timekeeping.
  */
 static __always_inline
-void __arm64_update_vsyscall(struct vdso_time_data *vdata)
+void __arch_update_vdso_clock(struct vdso_clock *vc)
 {
-	vdata->clock_data[CS_HRES_COARSE].mask	= VDSO_PRECISION_MASK;
-	vdata->clock_data[CS_RAW].mask		= VDSO_PRECISION_MASK;
+	vc->mask	= VDSO_PRECISION_MASK;
 }
-#define __arch_update_vsyscall __arm64_update_vsyscall
+#define __arch_update_vdso_clock __arch_update_vdso_clock
 
 /* The asm-generic header needs to be included after the definitions above */
 #include <asm-generic/vdso/vsyscall.h>

include/asm-generic/vdso/vsyscall.h

@@ -22,11 +22,11 @@ static __always_inline const struct vdso_rng_data *__arch_get_vdso_u_rng_data(vo
 
 #endif /* CONFIG_GENERIC_VDSO_DATA_STORE */
 
-#ifndef __arch_update_vsyscall
-static __always_inline void __arch_update_vsyscall(struct vdso_time_data *vdata)
+#ifndef __arch_update_vdso_clock
+static __always_inline void __arch_update_vdso_clock(struct vdso_clock *vc)
 {
 }
-#endif /* __arch_update_vsyscall */
+#endif /* __arch_update_vdso_clock */
 
 #ifndef __arch_sync_vdso_time_data
 static __always_inline void __arch_sync_vdso_time_data(struct vdso_time_data *vdata)

kernel/time/vsyscall.c

@@ -118,7 +118,8 @@ void update_vsyscall(struct timekeeper *tk)
 	if (clock_mode != VDSO_CLOCKMODE_NONE)
 		update_vdso_time_data(vdata, tk);
 
-	__arch_update_vsyscall(vdata);
+	__arch_update_vdso_clock(&vc[CS_HRES_COARSE]);
+	__arch_update_vdso_clock(&vc[CS_RAW]);
 
 	vdso_write_end(vdata);