• Catalin Marinas's avatar
    arm64: Introduce execute-only page access permissions · cab15ce6
    Catalin Marinas authored
    The ARMv8 architecture allows execute-only user permissions by clearing
    the PTE_UXN and PTE_USER bits. However, the kernel running on a CPU
    implementation without User Access Override (ARMv8.2 onwards) can still
    access such page, so execute-only page permission does not protect
    against read(2)/write(2) etc. accesses. Systems requiring such
    protection must enable features like SECCOMP.
    
    This patch changes the arm64 __P100 and __S100 protection_map[] macros
    to the new __PAGE_EXECONLY attributes. A side effect is that
    pte_user() no longer triggers for __PAGE_EXECONLY since PTE_USER isn't
    set. To work around this, the check is done on the PTE_NG bit via the
    pte_ng() macro. VM_READ is also checked now for page faults.
    Reviewed-by: default avatarWill Deacon <will.deacon@arm.com>
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    cab15ce6
fault.c 19.4 KB