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SubjectRe: [PATCH 03/10] ptrace: implement PTRACE_SEIZE
On 05/16, Tejun Heo wrote:
>
> @@ -315,6 +338,9 @@ static int ptrace_attach(struct task_struct *task)
> if (task_is_stopped(task)) {
> task->jobctl |= JOBCTL_TRAP_STOP | JOBCTL_TRAPPING;
> signal_wake_up(task, 1);
> + } else if (seize) {
> + task->jobctl |= JOBCTL_TRAP_STOP;

So, this can race with do_signal_stop(), it can clear TRAP_STOP and
JOBCTL_STOP_PENDING can guarantee the tracee will trap later.

> + * When PT_SEIZED, it's used for both group stop and explicit
> + * SEIZE/INTERRUPT traps. Both generate PTRACE_EVENT_STOP trap
> + * with accompanying siginfo.
> + *
> + * When !PT_SEIZED, it's used only for group stop trap with
> + * CLD_STOPPED as exit_code and no siginfo.
> */
> if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) {
> - signr = current->jobctl & JOBCTL_STOP_SIGMASK;
> - WARN_ON_ONCE(!signr);
> - ptrace_stop(signr, CLD_STOPPED, 0, NULL);
> - current->exit_code = 0;
> + if (current->ptrace & PT_SEIZED) {
> + ptrace_do_notify(SIGTRAP | PTRACE_EVENT_STOP << 8,
> + CLD_STOPPED);

So. When PT_SEIZED, we always report PTRACE_EVENT_STOP and PTRACE_GET_SIGINFO
always works.

Personally I agree, this looks more clean and natural.

Oleg.



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