linux-kernel - Re: [PATCH 0/2] Embedding Position Independent Executables

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Date:	Mon, 4 Apr 2016 10:57:57 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Dave Martin <Dave.Martin@....com>,
	Olof Johansson <olof@...om.net>,
	Doug Anderson <dianders@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>, Russ Dill <Russ.Dill@...com>
Subject: Re: [PATCH 0/2] Embedding Position Independent Executables

[Manually reformatted your email so I can reply to it sensibly - please
don't make me have to do this again, next time I'll ignore your message
as it's too much effort, thanks]

On Sun, Apr 03, 2016 at 09:23:52AM +0200, Alexandre Belloni wrote:
> Hi,
> 
> This series tries to revive the many series trying to achieve the same
> thing.
> 
> I've tried numerous approaches and while using the kernel module loader
> is actually quite convenient from a relocation point of view it is quite
> overkill and also it is quite often too late as a lot of the arch
> specific PM code assume that it is running at boot time, befor having
> access to any filesystem.
> 
> I've chosen to be less generic than what Russ did and only handle ARM.
> I reused the API he defined but I actually went closer to his first
> implementation by compiling and embedding a real PIE that doesn't
> actually need relocations (gcc seems to be better at it thanks to ASLR).
> 
> In this series, I'm also converting the AT91 suspend code to use that
> infrastructure as it is quite simple but I also toyed with more complex
> functions.
> 
> The current limitation is that is doesn't actually tries to handle big
> endian and I didn't test thumb (and this will probably require more work
> to get that working reliably).
> 
> Also, to be more useful prppoer handling of a stack has to be added
> (this is not too difficult and is planned) and will be enough to get
> rk3288 suspend/resume and DDR timing changes working.

Provided there is no linking back to the kernel image (which is enforced
by the --no-undefined flag), this at first glance looks okay, but what
is the motivation behind this change?  Just because there's "many series
trying to do this" isn't really a justification or a reason why we should
include this in the mainline kernel.

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
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