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

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Message-ID: <CAH9NwWdODq0GXWJb_4jQNhgWjjAYfZccGLLLe7a=LVC95ew2tQ@mail.gmail.com>
Date: Tue, 7 Jan 2025 11:17:04 +0100
From: Christian Gmeiner <christian.gmeiner@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: linux-hexagon@...r.kernel.org, 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>, Maíra Canal <mcanal@...lia.com>
Subject: Re: [PATCH] hexagon: fix using plain integer as NULL pointer warning
 in cmpxchg

Hi Willem,

>
> 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>

Closes: https://lore.kernel.org/oe-kbuild-all/202501031246.AD8Jjze0-lkp@intel.com/
Tested-by: Christian Gmeiner <cgmeiner@...lia.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
>
>


-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info/privacypolicy