linux-kernel - Re: [PATCH] x86, relocs: move ELF relocation handling to C

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Message-ID: <CAOJsxLH0VSoSS6eskyzG1roR3=GeHR4OcfBapq7nNFXqom6UNQ@mail.gmail.com>
Date:	Wed, 12 Jun 2013 20:01:25 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86 maintainers <x86@...nel.org>,
	David Woodhouse <David.Woodhouse@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Matt Fleming <matt.fleming@...el.com>,
	Alexander Duyck <alexander.h.duyck@...el.com>
Subject: Re: [PATCH] x86, relocs: move ELF relocation handling to C

On Wed, Jun 12, 2013 at 7:26 PM, Kees Cook <keescook@...omium.org> wrote:
> On Tue, Jun 11, 2013 at 11:27 PM, Pekka Enberg <penberg@...nel.org> wrote:
>> Hello Kees,
>>
>> On Tue, Jun 11, 2013 at 9:58 PM, Kees Cook <keescook@...omium.org> wrote:
>>> Moves the relocation handling into C, after decompression. This requires
>>> that the decompressed size is passed to the decompression routine as
>>> well so that relocations can be found. Only kernels that need relocation
>>> support will use the code.
>>>
>>> Based on work by Neill Clift and Michael Davidson.
>>>
>>> Signed-off-by: Kees Cook <keescook@...omium.org>
>>
>> How does the kernel benefit from this? Are there problems with the current
>> assembly code? Are you planning to improve the relocation code?
>
> Yes, this is continuing the work needed for 64-bit relocations,
> ultimately needed by KASLR. As part of the work, I was asked to move
> the relocation logic from assembly into C. Doing this means that there
> isn't any need for duplicating the logic in the 64-bit path (e.g.
> head_64.S).
>
> Since the other relocation work is already in the tree, I wanted to
> get these last two pieces in (one was a fix for the __vvar_page --
> separate patch, the other is this one, allowing 64-bit relocations to
> operate while also moving the logic into C).

OK, that's definitely changelog material.

I'm not that familiar with the code your touching but FWIW:

Reviewed-by: Pekka Enberg <penberg@...nel.org>
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