vdso: Move ENABLE_COMPAT_VDSO from core to arm64

The ENABLE_COMAPT_VDSO symbol is only used by arm64 and only for the
time-related functionality. There should be no new users, so it doesn't
need to be in the generic vDSO code.

Move the logic into arm64 architecture-specific code and replace the
explicit define by the standard '#ifdef __aarch64__'.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/all/20250826-vdso-cleanups-v1-3-d9b65750e49f@linutronix.de

Author: t-8ch

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

@@ -7,11 +7,10 @@
 
 #ifndef __ASSEMBLY__
 /*
- * Warning: This code is meant to be used with
- * ENABLE_COMPAT_VDSO only.
+ * Warning: This code is meant to be used from the compat vDSO only.
  */
-#ifndef ENABLE_COMPAT_VDSO
-#error This header is meant to be used with ENABLE_COMPAT_VDSO only
+#ifdef __arch64__
+#error This header is meant to be used with from the compat vDSO only
 #endif
 
 #ifdef dmb

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

@@ -2,8 +2,8 @@
 /*
  * Copyright (C) 2018 ARM Limited
  */
-#ifndef __ASM_VDSO_GETTIMEOFDAY_H
-#define __ASM_VDSO_GETTIMEOFDAY_H
+#ifndef __ASM_VDSO_COMPAT_GETTIMEOFDAY_H
+#define __ASM_VDSO_COMPAT_GETTIMEOFDAY_H
 
 #ifndef __ASSEMBLY__
 
@@ -163,4 +163,4 @@ static inline bool vdso_clocksource_ok(const struct vdso_clock *vc)
 
 #endif /* !__ASSEMBLY__ */
 
-#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
+#endif /* __ASM_VDSO_COMPAT_GETTIMEOFDAY_H */

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

@@ -5,6 +5,8 @@
 #ifndef __ASM_VDSO_GETTIMEOFDAY_H
 #define __ASM_VDSO_GETTIMEOFDAY_H
 
+#ifdef __aarch64__
+
 #ifndef __ASSEMBLY__
 
 #include <asm/alternative.h>
@@ -96,4 +98,10 @@ static __always_inline const struct vdso_time_data *__arch_get_vdso_u_time_data(
 
 #endif /* !__ASSEMBLY__ */
 
+#else /* !__aarch64__ */
+
+#include "compat_gettimeofday.h"
+
+#endif /* __aarch64__ */
+
 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */

arch/arm64/kernel/vdso32/Makefile

@@ -59,7 +59,6 @@ VDSO_CAFLAGS += -DDISABLE_BRANCH_PROFILING
 VDSO_CAFLAGS += -march=armv8-a
 
 VDSO_CFLAGS := $(VDSO_CAFLAGS)
-VDSO_CFLAGS += -DENABLE_COMPAT_VDSO=1
 # KBUILD_CFLAGS from top-level Makefile
 VDSO_CFLAGS += -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
                -fno-strict-aliasing -fno-common \

include/vdso/datapage.h

@@ -196,11 +196,7 @@ enum vdso_pages {
  * - clock_gettime_fallback(): fallback for clock_gettime.
  * - clock_getres_fallback(): fallback for clock_getres.
  */
-#ifdef ENABLE_COMPAT_VDSO
-#include <asm/vdso/compat_gettimeofday.h>
-#else
 #include <asm/vdso/gettimeofday.h>
-#endif /* ENABLE_COMPAT_VDSO */
 
 #else /* !__ASSEMBLY__ */