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Message-Id: <1453926929-17663-40-git-send-email-kamal@canonical.com> Date: Wed, 27 Jan 2016 12:31:40 -0800 From: Kamal Mostafa <kamal@...onical.com> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, kernel-team@...ts.ubuntu.com Cc: Will Deacon <will.deacon@....com>, Kamal Mostafa <kamal@...onical.com> Subject: [PATCH 4.2.y-ckt 039/268] arm64: mdscr_el1: avoid exposing DCC to userspace 4.2.8-ckt3 -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> [ kamal: 4.2-stable prereq for 60792ad arm64: kernel: enforce pmuserenr_el0 initialization and restore ] Signed-off-by: Kamal Mostafa <kamal@...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 39139a3..f28a1fe 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -156,7 +156,8 @@ 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: * -- 1.9.1
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