1 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 07d0df6bf768..cc79eff4a1ad 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -5,6 +5,7 @@
 #include <linux/sched.h>                /* For struct task_struct.  */
 #include <linux/err.h>                  /* for IS_ERR_VALUE */
 #include <linux/bug.h>                  /* For BUG_ON.  */
+#include <linux/pid_namespace.h>        /* For task_active_pid_ns.  */
 #include <uapi/linux/ptrace.h>
 
 /*
@@ -129,6 +130,37 @@ static inline void ptrace_event(int event, unsigned long message)
 }
 
 /**
+ * ptrace_event_pid - possibly stop for a ptrace event notification
+ * @event:      %PTRACE_EVENT_* value to report
+ * @pid:        process identifier for %PTRACE_GETEVENTMSG to return
+ *
+ * Check whether @event is enabled and, if so, report @event and @pid
+ * to the ptrace parent.  @pid is reported as the pid_t seen from the
+ * the ptrace parent's pid namespace.
+ *
+ * Called without locks.
+ */
+static inline void ptrace_event_pid(int event, struct pid *pid)
+{
+        /*
+         * FIXME: There's a potential race if a ptracer in a different pid
+         * namespace than parent attaches between computing message below and
+         * when we acquire tasklist_lock in ptrace_stop().  If this happens,
+         * the ptracer will get a bogus pid from PTRACE_GETEVENTMSG.
+         */
+        unsigned long message = 0;
+        struct pid_namespace *ns;
+
+        rcu_read_lock();
+        ns = task_active_pid_ns(rcu_dereference(current->parent));
+        if (ns)
+                message = pid_nr_ns(pid, ns);
+        rcu_read_unlock();
+
+        ptrace_event(event, message);
+}
+
+/**
  * ptrace_init_task - initialize ptrace state for a new child
  * @child:              new child task
  * @ptrace:             true if child should be ptrace'd by parent's tracer
@@ -302,6 +334,9 @@ static inline void user_single_step_siginfo(struct task_struct *tsk,
  * calling arch_ptrace_stop() when it would be superfluous.  For example,
  * if the thread has not been back to user mode since the last stop, the
  * thread state might indicate that nothing needs to be done.
+ *
+ * This is guaranteed to be invoked once before a task stops for ptrace and
+ * may include arch-specific operations necessary prior to a ptrace stop.
  */
 #define arch_ptrace_stop_needed(code, info)     (0)
 #endif