linux-kernel - [PATCH] hexagon: fix using plain integer as NULL pointer warning in cmpxchg

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Message-ID: <20241203221736.282020-1-willemdebruijn.kernel@gmail.com>
Date: Tue,  3 Dec 2024 17:17:34 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: linux-hexagon@...r.kernel.org
Cc: bcain@...cinc.com,
	linux-kernel@...r.kernel.org,
	dhowells@...hat.com,
	edumazet@...gle.com,
	Willem de Bruijn <willemb@...gle.com>,
	kernel test robot <lkp@...el.com>
Subject: [PATCH] hexagon: fix using plain integer as NULL pointer warning in cmpxchg

From: Willem de Bruijn <willemb@...gle.com>

Sparse reports

    net/ipv4/inet_diag.c:1511:17: sparse: sparse: Using plain integer as NULL pointer

Due to this code calling cmpxchg on a non-integer type
struct inet_diag_handler *

    return !cmpxchg((const struct inet_diag_handler**)&inet_diag_table[type],
                    NULL, h) ? 0 : -EEXIST;

While hexagon's cmpxchg assigns an integer value to a variable of this
type.

    __typeof__(*(ptr)) __oldval = 0;

Update this assignment to cast 0 to the correct type.

The original issue is easily reproduced at head with the below block,
and is absent after this change.

    make LLVM=1 ARCH=hexagon defconfig
    make C=1 LLVM=1 ARCH=hexagon net/ipv4/inet_diag.o

Fixes: 99a70aa051d2 ("Hexagon: Add processor and system headers")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202411091538.PGSTqUBi-lkp@intel.com/
Signed-off-by: Willem de Bruijn <willemb@...gle.com>
---
 arch/hexagon/include/asm/cmpxchg.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/hexagon/include/asm/cmpxchg.h b/arch/hexagon/include/asm/cmpxchg.h
index bf6cf5579cf4..9c58fb81f7fd 100644
--- a/arch/hexagon/include/asm/cmpxchg.h
+++ b/arch/hexagon/include/asm/cmpxchg.h
@@ -56,7 +56,7 @@ __arch_xchg(unsigned long x, volatile void *ptr, int size)
 	__typeof__(ptr) __ptr = (ptr);				\
 	__typeof__(*(ptr)) __old = (old);			\
 	__typeof__(*(ptr)) __new = (new);			\
-	__typeof__(*(ptr)) __oldval = 0;			\
+	__typeof__(*(ptr)) __oldval = (__typeof__(*(ptr))) 0;	\
 								\
 	asm volatile(						\
 		"1:	%0 = memw_locked(%1);\n"		\
-- 
2.47.0.338.g60cca15819-goog