Emulate Privileged Access Never (PAN)

Description

Enabling this option prevents the kernel from accessing user-space memory directly by pointing TTBR0_EL1 to a reserved zeroed area and reserved ASID. The user access routines restore the valid TTBR0_EL1 temporarily. This configuration is available from kernel 4.10, but may be available if backported by distros. The configuration that was used to build kernel is available at /boot/config-*. To check the configuration value for CONFIG_ARM64_SW_TTBR0_PAN, run the following command: grep CONFIG_ARM64_SW_TTBR0_PAN /boot/config-* For each kernel installed, a line with value "y" should be returned.

Rationale

The Privileged Access Never (PAN) is the ARM equivalent of the x86 Supervisor Mode Access Prevention (SMAP), and it prevents privileged acccess to user data unless explicitly enabled.