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    Subject[q] fundamental thing I am still missing about put_user().
    Hi,

    I have a question about writing to userspace buffers. Can I do this in
    read_kmem() (read method of /dev/kmem):

    if (verify_area(VERIFY_WRITE, buf, count))
    return -EFAULT;

    lock_kernel();
    write to user buf without any worries, even taking spinlocks if needed.
    unlock_kernel();

    If I can do this then it is very useful because we could then hold a
    spinlock in mm/vmalloc.c:vread() which means vmlist can be protected by a
    simple spinlock which means vmalloc()/vfree()/ioremap() (i.e. really
    vfree() and get_vm_area()) can be made SMP safe, i.e. without forcing
    callers to have lock/unlock_kernel().

    Thank you for your patient explanation :)
    ------
    Tigran A. Aivazian | http://www.sco.com
    Escalations Research Group | tel: +44-(0)1923-813796
    Santa Cruz Operation Ltd | http://www.ocston.org/~tigran


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