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    SubjectRe: Does this work? "dcprobes" an x86-hack simple djprobes-equivalent?
    Hi Karim,

    Thank you for new idea.
    I discussed your proposal deeply with my coworkers.

    I think your approach has following advantages/disadvantages/problem;
    <advantages>
    (a) Able to be inserted into the target address of the branch.
    (b) So, binary analysis tool becomes simple.
    <disadvantages>
    (c) Implementation is much complicated.
    (d) Highly depend on the x86 arch.
    (e) Bigger overhead than djprobe.
    (f) There will be side effect(*)
    <problem>
    (g) User applications can modify LDT. (ex. wine)

    I think the dcprobe will work, but, unfortunately, it has
    an vulnerability by the problem (g).

    (*) In the following code:
    ---
    a=0
    do {
    ...
    a++;
    }while (a <= 100)
    ---
    In case of inserting dcprobe at the 1st line (a=0),
    it will replace 2nd (or more) instructions.
    In this case, the fix up routine (based on int3)
    will be invoked one hundred times.

    Thanks,



    --
    Masami HIRAMATSU
    2nd Research Dept.
    Hitachi, Ltd., Systems Development Laboratory
    E-mail: masami.hiramatsu.pt@hitachi.com


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