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    SubjectRe: [PATCH 06/11] ptrace: make group stop state visible via PTRACE_GETSIGINFO
    On 05/10, Oleg Nesterov wrote:
    >
    > > @@ -540,6 +542,17 @@ static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
    > >
    > > error = 0;
    > > *info = *child->last_siginfo;
    > > +
    > > + /*
    > > + * If reporting ptrace trap for a seized tracee, enable reporting
    > > + * of info->si_pt_flags.
    > > + */
    > > + if ((child->ptrace & PT_SEIZED) &&
    > > + (info->si_code & (0x7f | ~0xffff)) == (__SI_TRAP | SIGTRAP)) {
    >
    > Can't we simply check (from->si_code & __SI_MASK) == __SI_TRAP ?
    >
    > > + /* report whether group stop is in effect w/ SI_STOPPED */
    > > + if (sig->group_stop_count || (sig->flags & SIGNAL_STOP_STOPPED))
    >
    > We have more and more "group_stop_count || SIGNAL_STOP_STOPPED" checks,
    > perhaps we should make a helper. Or at least invent the short name to
    > denote the group-stopped-or-in-progress to simplify the discussions ;)
    >
    >
    > Still, this is strange. With this change ptrace_getsiginfo() reports
    > the extra "volatile" info which wasn't reported by the tracee itself.
    > If the tracer does PTRACE_SETSIGINFO twice in a row, it can see the
    ^^^^^^^^^^^^^^^^^
    PTRACE_GETSIGINFO
    > different si_pt_flags's.

    Forgot to mention... Probably we can ignore this but the tracer can
    set/clear __SI_TRAP via PTRACE_SETSIGINFO, after that PTRACE_GETSIGINFO
    changes its behaviour.

    Oleg.



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