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Message-Id: <1454538786-12215-46-git-send-email-luis.henriques@canonical.com> Date: Wed, 3 Feb 2016 22:30:51 +0000 From: Luis Henriques <luis.henriques@...onical.com> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, kernel-team@...ts.ubuntu.com Cc: Will Deacon <will.deacon@....com>, Luis Henriques <luis.henriques@...onical.com> Subject: [PATCH 3.16.y-ckt 045/180] arm64: mdscr_el1: avoid exposing DCC to userspace 3.16.7-ckt24 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Will Deacon <will.deacon@....com> 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@....com> Signed-off-by: Luis Henriques <luis.henriques@...onical.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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