linux-kernel - Re: [PATCH] x86: tell the world boot

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Date:	Fri, 08 May 2015 18:23:52 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: tell the world boot_params is 16-byte aligned

On Fri, May 08 2015, Borislav Petkov <bp@...en8.de> wrote:

> On Fri, May 08, 2015 at 03:42:33PM +0200, Rasmus Villemoes wrote:
>> It doesn't matter much, but this disassembly makes me cry a little bit:
>> 
>> ffffffff81f21223 <copy_bootdata>:
>> ffffffff81f21223:       55                      push   %rbp
>> ffffffff81f21224:       48 c7 c0 40 c2 02 82    mov    $0xffffffff8202c240,%rax
>> ffffffff81f2122b:       48 89 fe                mov    %rdi,%rsi
>> ffffffff81f2122e:       a8 01                   test   $0x1,%al
>> 
>> The reason is that boot_params is defined with
>> __attribute__((aligned(16))) in boot/main.c, but other translation
>> units only see the packed attribute on the definition of struct
>> boot_params, so assume the worst. Making the de facto alignment public
>
> Wouldn't it be better if we put both attributes together, i.e.:

Sure, putting it on the type works as well. Either way is fine with me.

Rasmus
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