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From: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Kees Cook <keescook@chromium.org>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	Jann Horn <jannh@google.com>,
	Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
	Emese Revfy <re.emese@gmail.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] security: do not enable CONFIG_GCC_PLUGINS by default
Date: Fri, 14 Jun 2019 20:14:34 +0200	[thread overview]
Message-ID: <20190614201434.3fa4bb6d@primarylaptop.localdomain> (raw)
In-Reply-To: <20190614162811.o33yeq65ythjumrh@shell.armlinux.org.uk>


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On Fri, 14 Jun 2019 17:28:11 +0100
Russell King - ARM Linux admin <linux@armlinux.org.uk> wrote:
> I'm wondering whether this is sloppy wording or whether the author is
> really implying that they call the kernel decompressor with the MMU
> enabled, against the express instructions in
> Documentation/arm/Booting.
According to [1]
> If they are going against the express instructions, all bets are off.

More background on the decompressor patch:
- The "ANDROID: arm: decompressor: Flush tlb before swiching domain 0 to
  client mode" patch is needed anyway since 3.4 in any case, and
  according to the thread about it [1], the MMU is on at boot.
- There is a downstream u-boot port for the Galaxy SIII and other very
  similar devices, which doesn't setup the MMU at boot, but I'm not
  confident enough to test in on the devices I have. To test with
  u-boot I'd need to find a new device.
- If I don't manage to find a new device to test on, since there is
  already some setup code like arch/arm/boot/compressed/head-sa1100.S
  that deal with MMU that are enabled with the bootloader, are patches
  to add a new file like that still accepted? The big downside is that
  using something like that is probably incompatible with
  ARCH_MULTIPLATFORM.

References:
-----------
[1]http://lkml.iu.edu/hypermail/linux/kernel/1212.1/02099.html
[2]https://blog.forkwhiletrue.me/posts/an-almost-fully-libre-galaxy-s3/

Denis.

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  reply	other threads:[~2019-06-14 18:15 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190614145755.10926-1-GNUtoo@cyberdimension.org>
2019-06-14 16:05 ` [PATCH] security: do not enable CONFIG_GCC_PLUGINS by default Jann Horn
2019-06-14 16:12   ` Denis 'GNUtoo' Carikli
2019-06-14 16:28   ` Russell King - ARM Linux admin
2019-06-14 18:14     ` Denis 'GNUtoo' Carikli [this message]
2019-06-14 18:54       ` Russell King - ARM Linux admin
2019-06-15 10:13       ` Paul Kocialkowski
2019-06-21 23:42         ` Denis 'GNUtoo' Carikli
2019-06-24 13:31           ` Paul Kocialkowski
2019-06-15  3:08   ` Kees Cook

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