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    SubjectRe: [PATCH 2/2] Add new PTRACE_O_TRACESTOP option, make it control new ptrace behavior.
    On 09/05, Denys Vlasenko wrote:
    > Add new PTRACE_O_TRACESTOP option, make it control new ptrace behavior.
    > Introduce new ptrace option, PTRACE_O_TRACESTOP. This makes API
    > more symmetric: every PTRACE_EVENT_event has corresponding PTRACE_O_TRACEevent now,
    > as it used to have before PTRACE_SEIZE was introduced.
    > PTRACE_SEIZE does not assume PTRACE_O_TRACESTOP, but with this patch
    > it allows any PTRACE_O_opts to be set at attach time

    Well. This assumes that the only difference with PTRACE_SEIZE is the
    new stop/interrupt behaviour. I am not sure this is "safe" to assume.

    Tejun, what do you think?

    From the correctness pov, the patch is mostly correct. but you forgot
    to update ptrace_init_task(). I bet you didn't try to test the patch ;)

    > int ptrace_request(struct task_struct *child, long request,
    > unsigned long addr, unsigned long data)
    > {
    > - bool seized = child->ptrace & PT_SEIZED;
    > + bool stop_events_enabled = child->ptrace & PT_TRACE_STOP;

    May be ptrace_event_enabled(child, PTRACE_EVENT_STOP) looks better...
    The same about other PT_TRACE_STOP checks, although this is cosmetic.

    And. Given that you can set/clear PT_TRACE_STOP in ptrace_setoptions(),
    you need the locking.

    Just for example. do_signal_stop() calls ptrace_trap_notify() and hits
    WARN_ON_ONCE(!PT_TRACE_STOP) because it was cleared in between.


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      Last update: 2011-09-06 22:13    [W:2.215 / U:0.452 seconds]
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