linux-kernel - Re: [PATCH] MIPS: tools: Fix relocs tool compiler warnings

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Message-ID: <5763B898.7040502@imgtec.com>
Date:	Fri, 17 Jun 2016 09:45:12 +0100
From:	Matt Redfearn <matt.redfearn@...tec.com>
To:	Harvey Hunt <harvey.hunt@...tec.com>, <ralf@...ux-mips.org>
CC:	<linux-mips@...ux-mips.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] MIPS: tools: Fix relocs tool compiler warnings



On 16/06/16 16:35, Harvey Hunt wrote:
> When using clang as HOSTCC, the following warnings appear:
>
> In file included from arch/mips/boot/tools/relocs_64.c:27:0:
> arch/mips/boot/tools/relocs.c: In function ‘read_relocs’:
> arch/mips/boot/tools/relocs.c:397:4: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>      ELF_R_SYM(rel->r_info) = elf32_to_cpu(ELF_R_SYM(rel->r_info));
>      ^~~~~~~~~
> arch/mips/boot/tools/relocs.c:397:4: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
> arch/mips/boot/tools/relocs.c: In function ‘walk_relocs’:
> arch/mips/boot/tools/relocs.c:491:4: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>      Elf_Sym *sym = &sh_symtab[ELF_R_SYM(rel->r_info)];
>      ^~~~~~~
> arch/mips/boot/tools/relocs.c: In function ‘do_reloc’:
> arch/mips/boot/tools/relocs.c:502:2: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>    unsigned r_type = ELF_R_TYPE(rel->r_info);
>    ^~~~~~~~
> arch/mips/boot/tools/relocs.c: In function ‘do_reloc_info’:
> arch/mips/boot/tools/relocs.c:641:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>     rel_type(ELF_R_TYPE(rel->r_info)),
>     ^~~~~~~~
>
> Fix them by making Elf64_Mips_Rela a union
>
> Signed-off-by: Harvey Hunt <harvey.hunt@...tec.com>
> Cc: Matt Redfearn <matt.redfearn@...tec.com>
> Cc: linux-mips@...ux-mips.org
> Cc: linux-kernel@...r.kernel.org
> ---
>   arch/mips/boot/tools/relocs_64.c | 19 +++++++++++--------
>   1 file changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/arch/mips/boot/tools/relocs_64.c b/arch/mips/boot/tools/relocs_64.c
> index b671b5e..06066e6a 100644
> --- a/arch/mips/boot/tools/relocs_64.c
> +++ b/arch/mips/boot/tools/relocs_64.c
> @@ -9,17 +9,20 @@
>   
>   typedef uint8_t Elf64_Byte;
>   
> -typedef struct {
> -	Elf64_Word r_sym;	/* Symbol index.  */
> -	Elf64_Byte r_ssym;	/* Special symbol.  */
> -	Elf64_Byte r_type3;	/* Third relocation.  */
> -	Elf64_Byte r_type2;	/* Second relocation.  */
> -	Elf64_Byte r_type;	/* First relocation.  */
> +typedef union {
> +	struct {
> +		Elf64_Word r_sym;	/* Symbol index.  */
> +		Elf64_Byte r_ssym;	/* Special symbol.  */
> +		Elf64_Byte r_type3;	/* Third relocation.  */
> +		Elf64_Byte r_type2;	/* Second relocation.  */
> +		Elf64_Byte r_type;	/* First relocation.  */
> +	} fields;
> +	Elf64_Xword unused;
>   } Elf64_Mips_Rela;
>   
>   #define ELF_CLASS               ELFCLASS64
> -#define ELF_R_SYM(val)          (((Elf64_Mips_Rela *)(&val))->r_sym)
> -#define ELF_R_TYPE(val)         (((Elf64_Mips_Rela *)(&val))->r_type)
> +#define ELF_R_SYM(val)          (((Elf64_Mips_Rela *)(&val))->fields.r_sym)
> +#define ELF_R_TYPE(val)         (((Elf64_Mips_Rela *)(&val))->fields.r_type)
>   #define ELF_ST_TYPE(o)          ELF64_ST_TYPE(o)
>   #define ELF_ST_BIND(o)          ELF64_ST_BIND(o)
>   #define ELF_ST_VISIBILITY(o)    ELF64_ST_VISIBILITY(o)

Acked-by: Matt Redfearn <matt.redfearn@...tec.com>