linux-kernel - [PATCH 0/2] ARM: mm: allow for stricter kernel memory perms

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Date:	Thu, 13 Feb 2014 17:04:08 -0800
From:	Kees Cook <keescook@...omium.org>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	keescook@...omium.org, Russell King <linux@....linux.org.uk>,
	Laura Abbott <lauraa@...eaurora.org>,
	Larry Bassel <lbassel@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Christoffer Dall <cdall@...columbia.edu>,
	Marc Zyngier <marc.zyngier@....com>,
	Jonathan Austin <jonathan.austin@....com>,
	Simon Baatz <gmbnomis@...il.com>,
	Nicolas Pitre <nico@...aro.org>,
	Dave Martin <Dave.Martin@....com>,
	Will Deacon <will.deacon@....com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Jiang Liu <liuj97@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Vitaly Andrianov <vitalya@...com>, linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] ARM: mm: allow for stricter kernel memory perms

This series of patches allows the ARM kernel page tables to gain better
permission separation. With a fixed[1] CONFIG_ARM_PTDUMP enabled, you
can see the before and after in /sys/kernel/debug/kernel_page_tables.

Before:
---[ Kernel Mapping ]---
0xc0000000-0xc0800000           8M     RW x  SHD
0xc0800000-0xc1e00000          22M     RW NX SHD
0xc2000000-0xc3000000          16M     RW x  SHD
0xc3800000-0xd1000000         216M     RW x  SHD
0xd1800000-0xef800000         480M     RW x  SHD

After:
---[ Kernel Mapping ]---
0xc0000000-0xc0100000           1M     RW NX SHD
0xc0100000-0xc0700000           6M     ro x  SHD
0xc0700000-0xc0a00000           3M     ro NX SHD
0xc0a00000-0xc1e00000          20M     RW NX SHD
0xc2000000-0xc3000000          16M     RW NX SHD
0xc3800000-0xd1000000         216M     RW NX SHD
0xd1800000-0xef800000         480M     RW NX SHD

This is available via CONFIG_ARM_KERNMEM_PERMS and CONFIG_DEBUG_RODATA.
The latter exists to match the x86 option of the same name, and is
left as a configurable since each additional region adds more potential
memory padding.

The series is based on earlier work from Brad Spengler, Larry Bassel,
and Laura Abbott.

Thanks,

-Kees

[1] these patches are needed to get the correct output:
    https://lkml.org/lkml/2014/2/12/662
    https://lkml.org/lkml/2014/2/12/663

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