[PATCH v3 6/6] Makefile.extrawarn: turn on missing-prototypes globally

[Arnd Bergmann <arnd@kernel.org>]

From: Arnd Bergmann <arnd@arndb.de>

Over the years we went from > 1000 of warnings to under 100 earlier
this year, and I sent patches to address all the ones that I saw with
compile testing randcom configs on arm64, arm and x86 kernels. This is a
really useful warning, as it catches real bugs when there are mismatched
prototypes. In particular with kernel control flow integrity enabled,
those are no longer allowed.

I have done extensive testing to ensure that there are no new build
errors or warnings on any configuration of x86, arm and arm64 builds.
I also made sure that at least the both the normal defconfig and an
allmodconfig build is clean for arc, csky, loongarch, m68k, microblaze,
openrisc, parisc, powerpc, riscv, s390, and xtensa, with the respective
maintainers doing most of the patches.

At this point, there are five architectures with a number of known
regressions: alpha, nios2, mips, sh and sparc. In the previous version
of this patch, I had turned off the missing prototype warnings for the 15
architectures that still had issues, but since there are only five left,
I think we can leave the rest to the maintainers (Cc'd here) as well.

Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-alpha@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Link: https://lore.kernel.org/lkml/20230810141947.1236730-1-arnd@kernel.org/
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com> # RISC-V
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 scripts/Makefile.extrawarn | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 1527199161d7..8e9170f932ea 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -17,6 +17,8 @@ KBUILD_CFLAGS += -Wno-format-security
 KBUILD_CFLAGS += -Wno-trigraphs
 KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
 KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
+KBUILD_CFLAGS += -Wmissing-declarations
+KBUILD_CFLAGS += -Wmissing-prototypes
 
 ifneq ($(CONFIG_FRAME_WARN),0)
 KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
@@ -95,10 +97,8 @@ export KBUILD_EXTRA_WARN
 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
 
 KBUILD_CFLAGS += -Wextra -Wunused -Wno-unused-parameter
-KBUILD_CFLAGS += -Wmissing-declarations
 KBUILD_CFLAGS += $(call cc-option, -Wrestrict)
 KBUILD_CFLAGS += -Wmissing-format-attribute
-KBUILD_CFLAGS += -Wmissing-prototypes
 KBUILD_CFLAGS += -Wold-style-definition
 KBUILD_CFLAGS += -Wmissing-include-dirs
 KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
-- 
2.39.2