tree af0b5cedc6e042623346d4e82be24eda190626a1
parent 9ded63aaf83eba76e1a54ac02581c2badc497f1a
author James Morse <james.morse@arm.com> 1437588354 +0100
committer Will Deacon <will.deacon@arm.com> 1437991721 +0100

arm64: kernel: Add support for Privileged Access Never

'Privileged Access Never' is a new arm8.1 feature which prevents
privileged code from accessing any virtual address where read or write
access is also permitted at EL0.

This patch enables the PAN feature on all CPUs, and modifies {get,put}_user
helpers temporarily to permit access.

This will catch kernel bugs where user memory is accessed directly.
'Unprivileged loads and stores' using ldtrb et al are unaffected by PAN.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
[will: use ALTERNATIVE in asm and tidy up pan_enable check]
Signed-off-by: Will Deacon <will.deacon@arm.com>