From mboxrd@z Thu Jan  1 00:00:00 1970
From: mbohan@codeaurora.org (Michael Bohan)
Date: Tue, 12 Apr 2011 17:42:24 -0700
Subject: MT_HIGH_VECTOR mapping set read-only creating illegal access
Message-ID: <4DA4F170.4020009@codeaurora.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi,

In arch/arm/kernel/traps.c:set_tls() and arch/arm/include/asm/tls.h, 
some configurations allow for a assignment of address 0xffff0ff0. This 
address falls within the MT_HIGH_VECTORS mapping setup in 
devicemaps_init(). That mapping is explicitly made read-only. Thus, the 
kernel takes a segfault when writing in set_tls().

It looks like this disparity may have been introduced in this commit:

commit 36bb94ba36f332de767cfaa3af6a5136435a3a9c
Author: Russell King <rmk+kernel@arm.linux.org.uk>
Date:   Tue Nov 16 08:40:36 2010 +0000

     ARM: pgtable: provide RDONLY page table bit rather than WRITE bit

     Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Is there a reason this mapping must be read-only? Perhaps we could apply 
write access for these special cases only?

Thanks,
Mike

-- 
Employee of Qualcomm Innovation Center, Inc.
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