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    SubjectRe: [RFC] [PATCH 4/7] Uprobes Implementation
    On Mon, Jan 11, 2010 at 05:55:53PM +0530, Srikar Dronamraju wrote:
    > +static const struct utrace_engine_ops uprobe_utrace_ops = {
    > + .report_quiesce = uprobe_report_quiesce,
    > + .report_signal = uprobe_report_signal,
    > + .report_exit = uprobe_report_exit,
    > + .report_clone = uprobe_report_clone,
    > + .report_exec = uprobe_report_exec
    > +};

    So, as stated before, uprobe seems to handle too much standalone
    policies such as freeing on exec, always inherit on clone and never
    on fork. Such rules should be decided from uprobe clients not
    from uprobe itself and that makes it not enough flexible to
    be usable for now.

    For example if we want it to be usable by perf, we have two ways:

    - a trace event. Unfortunately, like I explained in a previous
    mail, this doesn't seem to be a suitable interface for this
    particular case.

    - a performance monitoring unit, with the existing unified interface
    struct pmu, usable by perf.

    Typically, to use it with perf toward a pmu, perf tools need to
    create a uprobe on perf process and activate its hook on the next exec.
    Thereafter, it's up to perf to decide if we inherit through clone
    and fork.

    Here I fear utrace and perf are going to collide.

    See how could be the final struct pmu (we need to extend it
    to support utrace):

    struct pmu {
    enable() -> called we schedule in a context where we want
    a uprobe to be active. Called very often
    disable() -> the above opposite

    /* Not yet existing callbacks */

    hook_task() -> called when a process is created which
    we want to activate our hook
    would be typically called once on
    exec if we have set enable_on_exec
    and also on clone()/fork()
    if we want to inherit.

    The above hook_task (could be divided in more precise callback events
    like hook_on_exec, hook_on_clone, etc...) would be needed by perf
    to drive correctly utrace and this is going to collide with utrace
    callbacks that notify execs and forks.

    Probably utrace can be kept for all the utrace breakpoint signal
    handling an so. But I guess the rest can be implemented on top
    of a struct pmu and driven by perf like we did with hardware
    breakpoints re-implementation.

    Just an idea.

     \ /
      Last update: 2010-01-12 06:39    [W:3.181 / U:0.176 seconds]
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