[PATCH] kexec: x86: struct x86_linux_param_header should be packed

[WANG Chao]

On 08/05/13 at 01:35pm, Vivek Goyal wrote:
> I think struct x86_linux_param_header should be packed. Strange that we
> did not do it so far. 
> 
> Without packing struct size was 3824 (decimal) on my x86_64 machine. With
> packing it is 3820. I think there was a padding of 4 bytes at the end. So
> it should be harmless.
> 
> I tried to introduce more fields and that introduced padding in the
> middle of structure and kexec stopped working and that's how I got to
> know that bootparam is not packed.

In this case that's true and x86_linux_param_header should be packed.

One more thing is,
in include/x86/x86-linux.h, we already define PACKED macro:
 #define PACKED __attribute__((packed))
But within x86-linux.h, both PACKED_and __attribute__((packed)) are used.

PACKED isn't used much time and __attribute__((packed)) is quite simple
and straightforward. Maybe it's time we can remove the macro and use
__attribute__((packed)) directly.

I can send another patch to address this if anyone thinks it's a good
idea.

Thanks
WANG Chao

> ---
>  include/x86/x86-linux.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: kexec-tools/include/x86/x86-linux.h
> ===================================================================
> --- kexec-tools.orig/include/x86/x86-linux.h	2013-08-05 13:28:33.999338740 -0400
> +++ kexec-tools/include/x86/x86-linux.h	2013-08-05 13:28:46.616475104 -0400
> @@ -198,7 +198,7 @@ struct x86_linux_param_header {
>  	struct 	edd_info eddbuf[EDDMAXNR];	/* 0xd00 */
>  						/* 0xeec */
>  #define COMMAND_LINE_SIZE 2048
> -};
> +} __attribute__ ((packed));
>  
>  struct x86_linux_faked_param_header {
>  	struct x86_linux_param_header hdr;	/* 0x00 */
> 
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