[lkml]   [2004]   [Jul]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: A question about PROT_NONE on ARM and ARM26
    On Wed, Jun 30, 2004 at 11:59:22PM +0100, Russell King wrote:
    > Ok, to fill in for just this bit, the domain covering user space mappings
    > always remains in "client" mode, so page protections are always checked.
    > PAGE_NONE does not have the "user" bit set, so both user space accesses
    > and ldrt/strt instructions will be unable to access the pages, which is
    > the desired behaviour.
    > However, plain ldr and str instructions will access the page, but
    > get_user/put_user doesn't use them, and copy_from_user/copy_to_user
    > are carefully crafted to ensure that we hit the necessary permission
    > checks for each page it touches on the first access.

    What if CONFIG_PREEMPT is enabled, and you get preempted after that
    first access, and another thread unmaps the page before you're
    finished with it?

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 14:04    [W:0.022 / U:0.056 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site