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    SubjectRe: linux-next: add utrace tree


    On Mon, 25 Jan 2010, Mark Wielaard wrote:
    >
    > And all these users have wishes to extend the current ptrace interface
    > mess. But nobody dares to extend ptrace in any direction because
    > fixing/cleaning up one of these use cases might break the others in
    > subtle and not so subtle ways. Which is why the utrace series of patches
    > is cleaning up all this stuff first.

    I call bullshit.

    You can clean up ptrace without introducing odd new interfaces and trying
    to sell it as some revolutionary new kernel interface that can do
    anything.

    I also call bullshit on the "ptrace() is so horribly nasty" argument. Yes,
    I've seen the code that uses ptrace in user space, and yes, it's nasty,
    but it's invariably _not_ nasty so much because ptrace itself is nasty,
    but because it's full of #ifdef so-and-so-os/so-and-so-arch, and the code
    is never cleaned up.

    There are a couple of obvious cases of ptrace being uglier-than-it-needs-
    to-be. Like the traditional ptrace read/write interface being purely "word
    at a time", and that clearly is not pretty. Several architectures already
    do "copy range" kind of versions on it, though, so that's just a detail,
    and if anybody wanted to clean it up, they could have.

    The more fundamental problem is the use of signals (while at the same time
    wanting to _trap_ non-ptrace signals), without any model for a "connection
    state", which is why you can have only one tracer. But again, that's
    largely a user interface issue, and apparently utrace does _nothing_ for
    that problem at all.

    So I do agree that ptrace is not a great interface. However: repeating
    that statement over and over in _no_ way excuses some totally unrelated
    code that doesn't have anything what-so-ever to do with the actual
    problems of ptrace.

    Linus


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