linux-kernel - Re: [PATCH] x86/KASLR: use the right memcpy

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Date:   Tue, 30 May 2017 21:56:56 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...omium.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Dave Jiang <dave.jiang@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/KASLR: use the right memcpy

On 05/30/17 at 11:14am, Arnd Bergmann wrote:
> The decompressor has its own implementation of the string functions,
> but has to include the right header to get those, while implicitly
> including linux/string.h may result in a link error:
> 
> arch/x86/boot/compressed/kaslr.o: In function `choose_random_location':
> kaslr.c:(.text+0xf51): undefined reference to `_mmx_memcpy'
> 
> This has appeared now as kaslr started using memcpy. Other files in the
> decompressor already do the same thing.
> 
> Fixes: d52e7d5a952c ("x86/KASLR: Parse all 'memmap=' boot option entries")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks for this fix, Arnd!

The linking error didn't happen when I tested the patch of d52e7d5a952c.
Could you tell in what condition it will be triggered? Not sure if I
should wait for this fix being merged and do a back porting, or can
defer it if it's not risky.

Thanks
Baoquan

> ---
>  arch/x86/boot/compressed/kaslr.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index e0eba12bffe7..fe318b44f7b8 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -30,6 +30,7 @@
>  
>  #include "misc.h"
>  #include "error.h"
> +#include "../string.h"
>  
>  #include <generated/compile.h>
>  #include <linux/module.h>
> -- 
> 2.9.0
>