[PATCH 2/2] arm64: SW PAN: Update saved ttbr0 value on enter_lazy_tlb

[Catalin Marinas]

On Wed, Dec 06, 2017 at 11:16:08AM +0000, Will Deacon wrote:
> enter_lazy_tlb is called when a kernel thread rides on the back of
> another mm, due to a context switch or an explicit call to unuse_mm
> where a call to switch_mm is elided.
> 
> In these cases, it's important to keep the saved ttbr value up to date
> with the active mm, otherwise we can end up with a stale value which
> points to a potentially freed page table.
> 
> This patch implements enter_lazy_tlb for arm64, so that the saved ttbr0
> is kept up-to-date with the active mm for kernel threads.
> 
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> Cc: Vinayak Menon <vinmenon at codeaurora.org>
> Reported-by: Vinayak Menon <vinmenon at codeaurora.org>
> Signed-off-by: Will Deacon <will.deacon at arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>