• Will Deacon's avatar
    ARM: mm: introduce present, faulting entries for PAGE_NONE · 960bd8ae
    Will Deacon authored
    commit 26ffd0d4 upstream.
    
    PROT_NONE mappings apply the page protection attributes defined by _P000
    which translate to PAGE_NONE for ARM. These attributes specify an XN,
    RDONLY pte that is inaccessible to userspace. However, on kernels
    configured without support for domains, such a pte *is* accessible to
    the kernel and can be read via get_user, allowing tasks to read
    PROT_NONE pages via syscalls such as read/write over a pipe.
    
    This patch introduces a new software pte flag, L_PTE_NONE, that is set
    to identify faulting, present entries.
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    [bwh: Backported to 3.2 as dependency of commit b6ccb980
     ('ARM: 7954/1: mm: remove remaining domain support from ARMv6'):
     - Drop 3-level changes
     - Adjust filename, context]
    Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
    960bd8ae
pgtable-2level.h 5.73 KB