linux-kernel - [PATCH] x86/boot: Add -Wno-pointer-sign to KBUILD

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Date:   Fri, 12 Oct 2018 18:07:14 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] x86/boot: Add -Wno-pointer-sign to KBUILD_CFLAGS

When compiling the kernel with Clang, this warning appears even though
it is disabled for the whole kernel because this folder has its own set
of KBUILD_CFLAGS. It was disabled before the beginning of git history.

In file included from arch/x86/boot/compressed/kaslr.c:29:
In file included from arch/x86/boot/compressed/misc.h:21:
In file included from ./include/linux/elf.h:5:
In file included from ./arch/x86/include/asm/elf.h:77:
In file included from ./arch/x86/include/asm/vdso.h:11:
In file included from ./include/linux/mm_types.h:9:
In file included from ./include/linux/spinlock.h:88:
In file included from ./arch/x86/include/asm/spinlock.h:43:
In file included from ./arch/x86/include/asm/qrwlock.h:6:
./include/asm-generic/qrwlock.h:101:53: warning: passing 'u32 *' (aka
'unsigned int *') to parameter of type 'int *' converts between pointers
to integer types with different sign [-Wpointer-sign]
        if (likely(atomic_try_cmpxchg_acquire(&lock->cnts, &cnts, _QW_LOCKED)))
                                                           ^~~~~
./include/linux/compiler.h:76:40: note: expanded from macro 'likely'
# define likely(x)      __builtin_expect(!!(x), 1)
                                            ^
./include/asm-generic/atomic-instrumented.h:69:66: note: passing
argument to parameter 'old' here
static __always_inline bool atomic_try_cmpxchg(atomic_t *v, int *old, int new)
                                                                 ^

Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---

There has been some discussion around whether KBUILD_CFLAGS should be
overwritten in the folder (few examples linked below). In the meantime,
there is precedent for taking top level disabled warnings and adding
them here, thus this patch.

* https://lore.kernel.org/lkml/CAKwvOdmXcztP542kADhyJYN2=Fk3qyXif_MCs=kqPGE8QtTjvQ@mail.gmail.com/
* https://lore.kernel.org/lkml/56442061-7f55-878d-5b26-7cdd14e901d2@zytor.com/

 arch/x86/boot/compressed/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 28764dacf018..466f66c8a7f8 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -37,6 +37,7 @@ KBUILD_CFLAGS += $(call cc-option,-ffreestanding)
 KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
 KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
 KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
+KBUILD_CFLAGS += -Wno-pointer-sign
 
 KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
-- 
2.19.1