[3.16.y-ckt stable] Patch "arm64: mdscr_el1: avoid exposing DCC to userspace" has been added to the 3.16.y-ckt tree
Luis Henriques
luis.henriques at canonical.com
Wed Feb 3 13:58:08 UTC 2016
This is a note to let you know that I have just added a patch titled
arm64: mdscr_el1: avoid exposing DCC to userspace
to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue
This patch is scheduled to be released in version 3.16.7-ckt24.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
---8<------------------------------------------------------------
>From 7cd61241142bedff53eeb1f220d8c81a64bc4ff4 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon at arm.com>
Date: Thu, 20 Aug 2015 11:47:13 +0100
Subject: arm64: mdscr_el1: avoid exposing DCC to userspace
commit d8d23fa0f27f3b2942a7bbc7378c7735324ed519 upstream.
We don't want to expose the DCC to userspace, particularly as there is
a kernel console driver for it.
This patch resets mdscr_el1 to disable userspace access to the DCC
registers on the cold boot path.
Signed-off-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
arch/arm64/mm/proc.S | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 7736779c9809..63cf428c6834 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -186,7 +186,8 @@ ENTRY(__cpu_setup)
mov x0, #3 << 20
msr cpacr_el1, x0 // Enable FP/ASIMD
- msr mdscr_el1, xzr // Reset mdscr_el1
+ mov x0, #1 << 12 // Reset mdscr_el1 and disable
+ msr mdscr_el1, x0 // access to the DCC from EL0
/*
* Memory region attributes for LPAE:
*
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