• James Morse's avatar
    arm64: kernel: Add support for User Access Override · 57f4959b
    James Morse authored
    'User Access Override' is a new ARMv8.2 feature which allows the
    unprivileged load and store instructions to be overridden to behave in
    the normal way.
    
    This patch converts {get,put}_user() and friends to use ldtr*/sttr*
    instructions - so that they can only access EL0 memory, then enables
    UAO when fs==KERNEL_DS so that these functions can access kernel memory.
    
    This allows user space's read/write permissions to be checked against the
    page tables, instead of testing addr<USER_DS, then using the kernel's
    read/write permissions.
    Signed-off-by: default avatarJames Morse <james.morse@arm.com>
    [catalin.marinas@arm.com: move uao_thread_switch() above dsb()]
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    57f4959b
copy_to_user.S 1.94 KB