Messages in this thread | | | Date | Wed, 26 Aug 2015 11:48:39 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH] arm: Handle starting up in secure mode |
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On Wed, Aug 26, 2015 at 11:39:42AM +0100, Dave Martin wrote: > On Mon, Aug 24, 2015 at 09:55:26AM -0400, 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. > > Up to now we've steered clear of this, since it's a bit of a fig leaf > for broken firmware unless Linux actually has some valid use for the > Security Extensions itself. > > Shouldn't the bootloader or firmware be doing this stuff, and if not, > why not? > > > Some other things that would need to be considered in any case: > > * SoC-specific setup of the Non-secure view of the system: This has > to happen very early, so making it DT aware is going to be hard -- > failing that, we are effectively risking bringing back board files. > The split in responsibility between firmware/bootloader and kernel > needs to be clearly defined and (as far as possible) platform- > independent, otherwise we'll have total chaos. > > * Out of reset, generally the CPU state is only fully defined for the > highest exception level. You probably need to be doing more setup > than you're currently doing. > > * SMP, secondary boot and suspend/resume -- again involving board- > specific code. > > * You need to safely "park" the Secure World before running anything > in Non-Secure. As a minimum, you would need to quiesce any > Secure interrupt sources, disable all interrupt traps to Monitor > mode, and make sure that the Monitor vectors point somewhere > real, so that executing SMC doesn't send the CPU off into the > long grass...
Another question is: has this been tested with kexec?
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