Re: [PATCH] arm: Handle starting up in secure mode

From: Daniel Thompson
Date: Thu Aug 27 2015 - 12:17:18 EST

On 24/08/15 14:55, Christopher Covington wrote:
ARM Linux appears to have never been made aware of the ARMv7 security
extensions. When CONFIG_ARM_SEC_EXT=y, have it probe for its security
state by checking whether CNTFRQ is writeable and potentially make
mode changes based on the information. The most features are available
from hypervisor (HYP) mode, so switch to it possible. Failing that,
prefer non-secure supervisor (SVC) mode to secure supervisor mode.

If there is no hypervisor mode available what benefit do we get from transitioning to non-secure mode?

When running in secure mode we retain access to some potentially useful features such as having access to FIQ.


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