From: Will Deacon Date: Thu, 20 Aug 2015 10:47:13 +0000 (+0100) Subject: arm64: mdscr_el1: avoid exposing DCC to userspace X-Git-Tag: v3.16.35~645 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7cd61241142bedff53eeb1f220d8c81a64bc4ff4;p=thirdparty%2Fkernel%2Fstable.git 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 Signed-off-by: Luis Henriques --- diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 7736779c98090..63cf428c68340 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: *