ptrace children revamp
ptrace no longer fiddles with the children/sibling links, and the old ptrace_children list is gone. Now ptrace, whether of one's own children or another's via PTRACE_ATTACH, just uses the new ptraced list instead. There should be no user-visible difference that matters. The only change is the order in which do_wait() sees multiple stopped children and stopped ptrace attachees. Since wait_task_stopped() was changed earlier so it no longer reorders the children list, we already know this won't cause any new problems. Signed-off-by: Roland McGrath <roland@redhat.com>
This commit is contained in:
Roland McGrath
Родитель
98abed0200
Коммит
f470021adb
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@ -140,8 +140,8 @@ extern struct group_info init_groups;
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.nr_cpus_allowed = NR_CPUS, \
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}, \
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.tasks = LIST_HEAD_INIT(tsk.tasks), \
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.ptrace_children= LIST_HEAD_INIT(tsk.ptrace_children), \
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.ptrace_list = LIST_HEAD_INIT(tsk.ptrace_list), \
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.ptraced = LIST_HEAD_INIT(tsk.ptraced), \
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.ptrace_entry = LIST_HEAD_INIT(tsk.ptrace_entry), \
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.real_parent = &tsk, \
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.parent = &tsk, \
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.children = LIST_HEAD_INIT(tsk.children), \
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@ -1062,12 +1062,6 @@ struct task_struct {
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#endif
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struct list_head tasks;
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/*
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* ptrace_list/ptrace_children forms the list of my children
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* that were stolen by a ptracer.
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*/
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struct list_head ptrace_children;
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struct list_head ptrace_list;
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struct mm_struct *mm, *active_mm;
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@ -1089,18 +1083,25 @@ struct task_struct {
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/*
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* pointers to (original) parent process, youngest child, younger sibling,
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* older sibling, respectively. (p->father can be replaced with
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* p->parent->pid)
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* p->real_parent->pid)
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*/
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struct task_struct *real_parent; /* real parent process (when being debugged) */
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struct task_struct *parent; /* parent process */
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struct task_struct *real_parent; /* real parent process */
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struct task_struct *parent; /* recipient of SIGCHLD, wait4() reports */
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/*
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* children/sibling forms the list of my children plus the
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* tasks I'm ptracing.
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* children/sibling forms the list of my natural children
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*/
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struct list_head children; /* list of my children */
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struct list_head sibling; /* linkage in my parent's children list */
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struct task_struct *group_leader; /* threadgroup leader */
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/*
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* ptraced is the list of tasks this task is using ptrace on.
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* This includes both natural children and PTRACE_ATTACH targets.
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* p->ptrace_entry is p's link on the p->parent->ptraced list.
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*/
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struct list_head ptraced;
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struct list_head ptrace_entry;
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/* PID/PID hash table linkage. */
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struct pid_link pids[PIDTYPE_MAX];
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struct list_head thread_group;
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@ -1876,9 +1877,6 @@ extern void wait_task_inactive(struct task_struct * p);
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#define wait_task_inactive(p) do { } while (0)
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#endif
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#define remove_parent(p) list_del_init(&(p)->sibling)
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#define add_parent(p) list_add_tail(&(p)->sibling,&(p)->parent->children)
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#define next_task(p) list_entry(rcu_dereference((p)->tasks.next), struct task_struct, tasks)
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#define for_each_process(p) \
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232
kernel/exit.c
232
kernel/exit.c
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@ -71,7 +71,7 @@ static void __unhash_process(struct task_struct *p)
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__get_cpu_var(process_counts)--;
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}
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list_del_rcu(&p->thread_group);
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remove_parent(p);
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list_del_init(&p->sibling);
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}
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/*
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@ -152,6 +152,18 @@ static void delayed_put_task_struct(struct rcu_head *rhp)
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put_task_struct(container_of(rhp, struct task_struct, rcu));
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}
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/*
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* Do final ptrace-related cleanup of a zombie being reaped.
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*
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* Called with write_lock(&tasklist_lock) held.
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*/
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static void ptrace_release_task(struct task_struct *p)
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{
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BUG_ON(!list_empty(&p->ptraced));
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ptrace_unlink(p);
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BUG_ON(!list_empty(&p->ptrace_entry));
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}
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void release_task(struct task_struct * p)
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{
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struct task_struct *leader;
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@ -160,8 +172,7 @@ repeat:
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atomic_dec(&p->user->processes);
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proc_flush_task(p);
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write_lock_irq(&tasklist_lock);
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ptrace_unlink(p);
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BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
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ptrace_release_task(p);
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__exit_signal(p);
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/*
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@ -315,9 +326,8 @@ static void reparent_to_kthreadd(void)
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ptrace_unlink(current);
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/* Reparent to init */
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remove_parent(current);
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current->real_parent = current->parent = kthreadd_task;
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add_parent(current);
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list_move_tail(¤t->sibling, ¤t->real_parent->children);
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/* Set the exit signal to SIGCHLD so we signal init on exit */
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current->exit_signal = SIGCHLD;
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@ -692,37 +702,71 @@ static void exit_mm(struct task_struct * tsk)
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mmput(mm);
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}
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static void
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reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
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/*
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* Detach all tasks we were using ptrace on.
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* Any that need to be release_task'd are put on the @dead list.
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*
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* Called with write_lock(&tasklist_lock) held.
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*/
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static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
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{
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struct task_struct *p, *n;
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list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
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__ptrace_unlink(p);
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if (p->exit_state != EXIT_ZOMBIE)
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continue;
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/*
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* If it's a zombie, our attachedness prevented normal
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* parent notification or self-reaping. Do notification
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* now if it would have happened earlier. If it should
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* reap itself, add it to the @dead list. We can't call
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* release_task() here because we already hold tasklist_lock.
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*
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* If it's our own child, there is no notification to do.
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*/
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if (!task_detached(p) && thread_group_empty(p)) {
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if (!same_thread_group(p->real_parent, parent))
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do_notify_parent(p, p->exit_signal);
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}
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if (task_detached(p)) {
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/*
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* Mark it as in the process of being reaped.
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*/
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p->exit_state = EXIT_DEAD;
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list_add(&p->ptrace_entry, dead);
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}
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}
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}
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/*
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* Finish up exit-time ptrace cleanup.
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*
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* Called without locks.
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*/
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static void ptrace_exit_finish(struct task_struct *parent,
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struct list_head *dead)
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{
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struct task_struct *p, *n;
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BUG_ON(!list_empty(&parent->ptraced));
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list_for_each_entry_safe(p, n, dead, ptrace_entry) {
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list_del_init(&p->ptrace_entry);
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release_task(p);
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}
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}
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static void reparent_thread(struct task_struct *p, struct task_struct *father)
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{
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if (p->pdeath_signal)
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/* We already hold the tasklist_lock here. */
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group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
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/* Move the child from its dying parent to the new one. */
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if (unlikely(traced)) {
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/* Preserve ptrace links if someone else is tracing this child. */
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list_del_init(&p->ptrace_list);
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if (ptrace_reparented(p))
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list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
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} else {
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/* If this child is being traced, then we're the one tracing it
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* anyway, so let go of it.
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*/
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p->ptrace = 0;
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remove_parent(p);
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p->parent = p->real_parent;
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add_parent(p);
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if (task_is_traced(p)) {
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/*
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* If it was at a trace stop, turn it into
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* a normal stop since it's no longer being
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* traced.
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*/
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ptrace_untrace(p);
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}
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}
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list_move_tail(&p->sibling, &p->real_parent->children);
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/* If this is a threaded reparent there is no need to
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* notify anyone anything has happened.
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@ -737,7 +781,8 @@ reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
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/* If we'd notified the old parent about this child's death,
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* also notify the new parent.
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*/
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if (!traced && p->exit_state == EXIT_ZOMBIE &&
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if (!ptrace_reparented(p) &&
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p->exit_state == EXIT_ZOMBIE &&
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!task_detached(p) && thread_group_empty(p))
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do_notify_parent(p, p->exit_signal);
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@ -754,12 +799,15 @@ reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
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static void forget_original_parent(struct task_struct *father)
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{
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struct task_struct *p, *n, *reaper = father;
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struct list_head ptrace_dead;
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INIT_LIST_HEAD(&ptrace_dead);
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LIST_HEAD(ptrace_dead);
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write_lock_irq(&tasklist_lock);
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/*
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* First clean up ptrace if we were using it.
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*/
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ptrace_exit(father, &ptrace_dead);
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do {
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reaper = next_thread(reaper);
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if (reaper == father) {
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@ -768,58 +816,19 @@ static void forget_original_parent(struct task_struct *father)
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}
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} while (reaper->flags & PF_EXITING);
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/*
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* There are only two places where our children can be:
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*
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* - in our child list
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* - in our ptraced child list
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*
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* Search them and reparent children.
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*/
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list_for_each_entry_safe(p, n, &father->children, sibling) {
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int ptrace;
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ptrace = p->ptrace;
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/* if father isn't the real parent, then ptrace must be enabled */
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BUG_ON(father != p->real_parent && !ptrace);
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if (father == p->real_parent) {
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/* reparent with a reaper, real father it's us */
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p->real_parent = reaper;
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reparent_thread(p, father, 0);
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} else {
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/* reparent ptraced task to its real parent */
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__ptrace_unlink (p);
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if (p->exit_state == EXIT_ZOMBIE && !task_detached(p) &&
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thread_group_empty(p))
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do_notify_parent(p, p->exit_signal);
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}
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/*
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* if the ptraced child is a detached zombie we must collect
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* it before we exit, or it will remain zombie forever since
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* we prevented it from self-reap itself while it was being
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* traced by us, to be able to see it in wait4.
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*/
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if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && task_detached(p)))
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list_add(&p->ptrace_list, &ptrace_dead);
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}
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list_for_each_entry_safe(p, n, &father->ptrace_children, ptrace_list) {
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p->real_parent = reaper;
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reparent_thread(p, father, 1);
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if (p->parent == father) {
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BUG_ON(p->ptrace);
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p->parent = p->real_parent;
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}
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reparent_thread(p, father);
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}
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write_unlock_irq(&tasklist_lock);
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BUG_ON(!list_empty(&father->children));
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BUG_ON(!list_empty(&father->ptrace_children));
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list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_list) {
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list_del_init(&p->ptrace_list);
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release_task(p);
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}
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ptrace_exit_finish(father, &ptrace_dead);
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}
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/*
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@ -1180,13 +1189,6 @@ static int eligible_child(enum pid_type type, struct pid *pid, int options,
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return 0;
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}
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/*
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* Do not consider detached threads that are
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* not ptraced:
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*/
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if (task_detached(p) && !p->ptrace)
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return 0;
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/* Wait for all children (clone and not) if __WALL is set;
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* otherwise, wait for clone children *only* if __WCLONE is
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* set; otherwise, wait for non-clone children *only*. (Note:
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|
|
@ -1399,7 +1401,7 @@ static int wait_task_zombie(struct task_struct *p, int options,
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* the lock and this task is uninteresting. If we return nonzero, we have
|
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* released the lock and the system call should return.
|
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*/
|
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static int wait_task_stopped(struct task_struct *p,
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static int wait_task_stopped(int ptrace, struct task_struct *p,
|
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int options, struct siginfo __user *infop,
|
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int __user *stat_addr, struct rusage __user *ru)
|
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{
|
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|
|
@ -1407,7 +1409,7 @@ static int wait_task_stopped(struct task_struct *p,
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uid_t uid = 0; /* unneeded, required by compiler */
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pid_t pid;
|
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|
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if (!(p->ptrace & PT_PTRACED) && !(options & WUNTRACED))
|
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if (!(options & WUNTRACED))
|
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return 0;
|
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|
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exit_code = 0;
|
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|
|
@ -1416,7 +1418,7 @@ static int wait_task_stopped(struct task_struct *p,
|
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if (unlikely(!task_is_stopped_or_traced(p)))
|
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goto unlock_sig;
|
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|
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if (!(p->ptrace & PT_PTRACED) && p->signal->group_stop_count > 0)
|
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if (!ptrace && p->signal->group_stop_count > 0)
|
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/*
|
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* A group stop is in progress and this is the group leader.
|
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* We won't report until all threads have stopped.
|
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|
|
@ -1445,7 +1447,7 @@ unlock_sig:
|
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*/
|
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get_task_struct(p);
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pid = task_pid_vnr(p);
|
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why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
|
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why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
|
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read_unlock(&tasklist_lock);
|
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|
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if (unlikely(options & WNOWAIT))
|
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|
|
@ -1536,7 +1538,7 @@ static int wait_task_continued(struct task_struct *p, int options,
|
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* Returns zero if the search for a child should continue;
|
||||
* then *@notask_error is 0 if @p is an eligible child, or still -ECHILD.
|
||||
*/
|
||||
static int wait_consider_task(struct task_struct *parent,
|
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static int wait_consider_task(struct task_struct *parent, int ptrace,
|
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struct task_struct *p, int *notask_error,
|
||||
enum pid_type type, struct pid *pid, int options,
|
||||
struct siginfo __user *infop,
|
||||
|
|
@ -1546,6 +1548,15 @@ static int wait_consider_task(struct task_struct *parent,
|
|||
if (ret <= 0)
|
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return ret;
|
||||
|
||||
if (likely(!ptrace) && unlikely(p->ptrace)) {
|
||||
/*
|
||||
* This child is hidden by ptrace.
|
||||
* We aren't allowed to see it now, but eventually we will.
|
||||
*/
|
||||
*notask_error = 0;
|
||||
return 0;
|
||||
}
|
||||
|
||||
if (p->exit_state == EXIT_DEAD)
|
||||
return 0;
|
||||
|
||||
|
|
@ -1562,7 +1573,8 @@ static int wait_consider_task(struct task_struct *parent,
|
|||
*notask_error = 0;
|
||||
|
||||
if (task_is_stopped_or_traced(p))
|
||||
return wait_task_stopped(p, options, infop, stat_addr, ru);
|
||||
return wait_task_stopped(ptrace, p, options,
|
||||
infop, stat_addr, ru);
|
||||
|
||||
return wait_task_continued(p, options, infop, stat_addr, ru);
|
||||
}
|
||||
|
|
@ -1583,11 +1595,16 @@ static int do_wait_thread(struct task_struct *tsk, int *notask_error,
|
|||
struct task_struct *p;
|
||||
|
||||
list_for_each_entry(p, &tsk->children, sibling) {
|
||||
int ret = wait_consider_task(tsk, p, notask_error,
|
||||
type, pid, options,
|
||||
infop, stat_addr, ru);
|
||||
if (ret)
|
||||
return ret;
|
||||
/*
|
||||
* Do not consider detached threads.
|
||||
*/
|
||||
if (!task_detached(p)) {
|
||||
int ret = wait_consider_task(tsk, 0, p, notask_error,
|
||||
type, pid, options,
|
||||
infop, stat_addr, ru);
|
||||
if (ret)
|
||||
return ret;
|
||||
}
|
||||
}
|
||||
|
||||
return 0;
|
||||
|
|
@ -1601,21 +1618,16 @@ static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
|
|||
struct task_struct *p;
|
||||
|
||||
/*
|
||||
* If we never saw an eligile child, check for children stolen by
|
||||
* ptrace. We don't leave -ECHILD in *@notask_error if there are any,
|
||||
* because we will eventually be allowed to wait for them again.
|
||||
* Traditionally we see ptrace'd stopped tasks regardless of options.
|
||||
*/
|
||||
if (!*notask_error)
|
||||
return 0;
|
||||
options |= WUNTRACED;
|
||||
|
||||
list_for_each_entry(p, &tsk->ptrace_children, ptrace_list) {
|
||||
int ret = eligible_child(type, pid, options, p);
|
||||
if (unlikely(ret < 0))
|
||||
list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
|
||||
int ret = wait_consider_task(tsk, 1, p, notask_error,
|
||||
type, pid, options,
|
||||
infop, stat_addr, ru);
|
||||
if (ret)
|
||||
return ret;
|
||||
if (ret) {
|
||||
*notask_error = 0;
|
||||
return 0;
|
||||
}
|
||||
}
|
||||
|
||||
return 0;
|
||||
|
|
|
|||
|
|
@ -1125,8 +1125,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
|
|||
*/
|
||||
p->group_leader = p;
|
||||
INIT_LIST_HEAD(&p->thread_group);
|
||||
INIT_LIST_HEAD(&p->ptrace_children);
|
||||
INIT_LIST_HEAD(&p->ptrace_list);
|
||||
INIT_LIST_HEAD(&p->ptrace_entry);
|
||||
INIT_LIST_HEAD(&p->ptraced);
|
||||
|
||||
/* Now that the task is set up, run cgroup callbacks if
|
||||
* necessary. We need to run them before the task is visible
|
||||
|
|
@ -1198,7 +1198,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
|
|||
}
|
||||
|
||||
if (likely(p->pid)) {
|
||||
add_parent(p);
|
||||
list_add_tail(&p->sibling, &p->real_parent->children);
|
||||
if (unlikely(p->ptrace & PT_PTRACED))
|
||||
__ptrace_link(p, current->parent);
|
||||
|
||||
|
|
|
|||
|
|
@ -33,13 +33,9 @@
|
|||
*/
|
||||
void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
|
||||
{
|
||||
BUG_ON(!list_empty(&child->ptrace_list));
|
||||
if (child->parent == new_parent)
|
||||
return;
|
||||
list_add(&child->ptrace_list, &child->parent->ptrace_children);
|
||||
remove_parent(child);
|
||||
BUG_ON(!list_empty(&child->ptrace_entry));
|
||||
list_add(&child->ptrace_entry, &new_parent->ptraced);
|
||||
child->parent = new_parent;
|
||||
add_parent(child);
|
||||
}
|
||||
|
||||
/*
|
||||
|
|
@ -73,12 +69,8 @@ void __ptrace_unlink(struct task_struct *child)
|
|||
BUG_ON(!child->ptrace);
|
||||
|
||||
child->ptrace = 0;
|
||||
if (ptrace_reparented(child)) {
|
||||
list_del_init(&child->ptrace_list);
|
||||
remove_parent(child);
|
||||
child->parent = child->real_parent;
|
||||
add_parent(child);
|
||||
}
|
||||
child->parent = child->real_parent;
|
||||
list_del_init(&child->ptrace_entry);
|
||||
|
||||
if (task_is_traced(child))
|
||||
ptrace_untrace(child);
|
||||
|
|
@ -492,15 +484,34 @@ int ptrace_traceme(void)
|
|||
/*
|
||||
* Are we already being traced?
|
||||
*/
|
||||
repeat:
|
||||
task_lock(current);
|
||||
if (!(current->ptrace & PT_PTRACED)) {
|
||||
/*
|
||||
* See ptrace_attach() comments about the locking here.
|
||||
*/
|
||||
unsigned long flags;
|
||||
if (!write_trylock_irqsave(&tasklist_lock, flags)) {
|
||||
task_unlock(current);
|
||||
do {
|
||||
cpu_relax();
|
||||
} while (!write_can_lock(&tasklist_lock));
|
||||
goto repeat;
|
||||
}
|
||||
|
||||
ret = security_ptrace(current->parent, current,
|
||||
PTRACE_MODE_ATTACH);
|
||||
|
||||
/*
|
||||
* Set the ptrace bit in the process ptrace flags.
|
||||
* Then link us on our parent's ptraced list.
|
||||
*/
|
||||
if (!ret)
|
||||
if (!ret) {
|
||||
current->ptrace |= PT_PTRACED;
|
||||
__ptrace_link(current, current->real_parent);
|
||||
}
|
||||
|
||||
write_unlock_irqrestore(&tasklist_lock, flags);
|
||||
}
|
||||
task_unlock(current);
|
||||
return ret;
|
||||
|
|
|
|||
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