[PATCH] arm64: vdso: Fix "no previous prototype" warning

[Vincenzo Frascino]

If compiling the arm64 kernel with W=1 the following warning is produced:

| arch/arm64/kernel/vdso/vgettimeofday.c:9:5: error: no previous prototype for ‘__kernel_clock_gettime’ [-Werror=missing-prototypes]
|     9 | int __kernel_clock_gettime(clockid_t clock,
|       |     ^~~~~~~~~~~~~~~~~~~~~~
| arch/arm64/kernel/vdso/vgettimeofday.c:15:5: error: no previous prototype for ‘__kernel_gettimeofday’ [-Werror=missing-prototypes]
|    15 | int __kernel_gettimeofday(struct __kernel_old_timeval *tv,
|       |     ^~~~~~~~~~~~~~~~~~~~~
| arch/arm64/kernel/vdso/vgettimeofday.c:21:5: error: no previous prototype for ‘__kernel_clock_getres’ [-Werror=missing-prototypes]
|    21 | int __kernel_clock_getres(clockid_t clock_id,
|       |     ^~~~~~~~~~~~~~~~~~~~~

This patch removes "-Wmissing-prototypes" and "-Wmissing-declarations" compilers
flags from the compilation of vgettimeofday.c to make possible to build the
kernel with CONFIG_WERROR enabled.

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Suggested-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
---
 arch/arm64/kernel/vdso/Makefile | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 60813497a381..172452f79e46 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -29,8 +29,11 @@ ldflags-y := -shared -soname=linux-vdso.so.1 --hash-style=sysv	\
 ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18
 ccflags-y += -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
 
+# -Wmissing-prototypes and -Wmissing-declarations are removed from
+# the CFLAGS of vgettimeofday.c to make possible to build the
+# kernel with CONFIG_WERROR enabled.
 CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) $(GCC_PLUGINS_CFLAGS) \
-				$(CC_FLAGS_LTO)
+				$(CC_FLAGS_LTO) -Wmissing-prototypes -Wmissing-declarations
 KASAN_SANITIZE			:= n
 KCSAN_SANITIZE			:= n
 UBSAN_SANITIZE			:= n
-- 
2.34.1