Re: [PATCH v3 06/20] arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN

Yisheng Xie
2018-01-17T02:58:58Z

Hi Will,

On 2017/12/6 20:35, Will Deacon wrote:
> config ARM64_SW_TTBR0_PAN
> bool "Emulate Privileged Access Never using TTBR0_EL1 switching"
> - depends on BROKEN # Temporary while switch_mm is reworked
> help
> Enabling this option prevents the kernel from accessing
> user-space memory directly by pointing TTBR0_EL1 to a reserved

I have a question not related to this patch itself, but to ARM64_SW_TTBR0_PAN:

What does ARM64_SW_TTBR0_PAN used for? I means is hardware support PAN, do we
still need SW_TTBR0_PAN?

And if the hardware do not support PAN, is SW_TTBR0_PAN is *must* option? or
there maybe a security risk?

Thanks
Yisheng Xie