[PATCH v10 4/6] ARM: add vdso user-space code
catalin.marinas at arm.com
Tue Feb 24 02:17:55 PST 2015
On Fri, Feb 20, 2015 at 04:52:16PM -0500, Christopher Covington wrote:
> On 02/18/2015 07:12 AM, Venkappa Mala wrote:
> > Catalin Marinas <catalin.marinas <at> arm.com> writes:
> >> IIRC there were some discussions about Linux booting in secure mode on
> >> ARMv7 with no firmware to initialise the Hyp registers. If that's the
> >> case for you, we could restart that discussion and try to initialise
> >> CNTVOFF in the kernel running in _secure_ mode (possibly with some CPU
> >> notifiers in the generic timer code).
> > My test environment is like CNTVOFF initialization is not taken care in
> > the firmware, HYP mode is disabled and kernel is booted with Secure SVC
> > PL1 mode. As you have mentioned about restarting the thread, perhaps, it
> > will be good to have a discussion in the following thread rather than
> > restarting the thread.
> > arm: Handle starting up in secure mode
> > https://lkml.org/lkml/2014/9/16/552
> > May I know your opinion about this one?
> Catalin pointed out that accesses to NSACR may trap. I have not yet found a
> reason why trying to write to CNTFRQ wouldn't work.
Writing CNTFRQ from non-secure mode would trap as well. For whatever
reason, the architecture doesn't allow you to easily detect whether the
code runs in secure or non-secure mode (unless it is EL2/Hyp which is
always non-secure). The detection mechanism would have to involve
trapping of an undefined instruction but it doesn't need to be done
early during boot.
Otherwise, I think in the arch timer code we could do something like:
if (!is_hyp_mode_available() && !arch_timer_user_virtual &&
* Assume the kernel is running in secure mode. Program
* the CNVOFF and CNTFRQ registers.
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