Re: [PATCH -next 0/3] replace open coded VA->PA calculation

From: Ard Biesheuvel <ardb@kernel.org>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Gaosheng Cui <cuigaosheng1@huawei.com>,
	 Russell King - ARM Linux <linux@armlinux.org.uk>,
	 Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
	 Gregory CLEMENT <gregory.clement@bootlin.com>,
	 Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
	Viresh Kumar <vireshk@kernel.org>,
	 Shiraz Hashim <shiraz.linux.kernel@gmail.com>,
	SoC Team <soc@kernel.org>,
	 Linus Walleij <linus.walleij@linaro.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	 "moderated list:ARM/SAMSUNG EXYNOS ARM ARCHITECTURES"
	<linux-samsung-soc@vger.kernel.org>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	gongruiqi1@huawei.com,  wangweiyang2@huawei.com
Subject: Re: [PATCH -next 0/3] replace open coded VA->PA calculation
Date: Mon, 20 Dec 2021 19:16:22 +0100	[thread overview]
Message-ID: <CAMj1kXH15CDm1no41V-VvS6-jYLv72R65SPZfBbVAeWWhmR0KA@mail.gmail.com> (raw)
In-Reply-To: <YcDGDLScE+3ZlU8/@lunn.ch>

On Mon, 20 Dec 2021 at 19:06, Andrew Lunn <andrew@lunn.ch> wrote:
>
> On Mon, Dec 20, 2021 at 04:39:43PM +0100, Arnd Bergmann wrote:
> > On Sat, Dec 18, 2021 at 9:58 AM Gaosheng Cui <cuigaosheng1@huawei.com> wrote:
> > >
> > > These patches replace an open coded calculation to obtain the physical
> > > address of a far symbol with a call to the new ldr_l etc macro, and they
> > > belong to the kaslr patch set of arm32.
> > >
> > > Reference: https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=arm-kaslr-latest
> > >
> > > Ard Biesheuvel (3):
> > >   arm-soc: exynos: replace open coded VA->PA conversions
> > >   arm-soc: mvebu: replace open coded VA->PA conversion
> > >   arm-soc: various: replace open coded VA->PA calculation
> >
> > Usually these patches should go through the respective platform
> > maintainer trees,
> > and from there into the soc tree, but time is a little short here.
> >
> > I could apply them directly with the maintainer Acks
>
> Sorry, but this is too low level for me to understand what is going
> on, and so feel confident actually giving an ACK for the mvebu change.
>
> Should the resulting assembly be exactly the same? Has the submitter
> disassembled the object code and shown there is no actual difference
> in the assembler output?
>

The assembly does not stay the same, that is really the point of these
patches: to replace hard to understand pointer arithmetic with simple
position independent macro invocations.

However, I don't think it really makes sense at this point to merge
these: the KASLR patches are ancient and never constituted more than a
proof of concept, so grabbing bits and pieces of it arbitrarily seems
rather pointless. Note that there is an effort underway to implement a
4/4 VM split for ARM, which has a huge impact on KASLR, and so those
changes need a lot of work and discussion before we can proceed with
them.

So in summary, NACK for this series.