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    SubjectRe: [RFC] syscalls, x86: Add __NR_kcmp syscall
    On Wed, Jan 18, 2012 at 03:29:50PM -0800, Eric W. Biederman wrote:
    > >
    > > It doesn't matter. Even if we take a list of objects the kernel either
    > > should return us some ordering info or find duplicates, in any case it
    > > makes things more complex i think. So we wanted to bring some minimum
    > > into kernel leaving the rest of work to user-space.
    >
    > Agreed a syscall does the duplication is probably not the way to go.
    >
    > A syscall that takes a huge list of objects would solve any security
    > concerns that we have with returning the object order to user space if
    > done carefully, but it would require a bunch of additional user space
    > and kernel memory.
    >

    yes, an it increase syscall time itself since we will have to provide
    this memory dynamically

    > Sometimes taking a data structure transforming it into a weird form for
    > a specific task and then transforming the data structure back to it's
    > original form is a useful way to go. So I think a general kernel object
    > deduplicating system call is an interesting plan B, but a straight
    > comparison function if we can make it work is a lot more flexible and
    > useful.
    >

    I hope the root-only restriction would resolve the potential security
    problem, since as I mentioned if I've hijacked the machine and already
    goot root -- mem order is not that interesting info I could obtain from
    such computer :)

    Cyrill


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