diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index ad754d1e0b13..4f224f169524 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -49,6 +49,7 @@
#define PTRACE_SEIZE 0x4206
#define PTRACE_INTERRUPT 0x4207
+#define PTRACE_LISTEN 0x4208
/* flags in @data for PTRACE_SEIZE */
#define PTRACE_SEIZE_DEVEL 0x80000000 /* temp flag for development */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1854def284f5..87f7ca7ed6f6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1813,6 +1813,7 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
#define JOBCTL_TRAP_STOP_BIT 19 /* trap for STOP */
#define JOBCTL_TRAP_NOTIFY_BIT 20 /* trap for NOTIFY */
#define JOBCTL_TRAPPING_BIT 21 /* switching to TRACED */
+#define JOBCTL_LISTENING_BIT 22 /* ptracer is listening for events */
#define JOBCTL_STOP_DEQUEUED (1 << JOBCTL_STOP_DEQUEUED_BIT)
#define JOBCTL_STOP_PENDING (1 << JOBCTL_STOP_PENDING_BIT)
@@ -1820,6 +1821,7 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
#define JOBCTL_TRAP_STOP (1 << JOBCTL_TRAP_STOP_BIT)
#define JOBCTL_TRAP_NOTIFY (1 << JOBCTL_TRAP_NOTIFY_BIT)
#define JOBCTL_TRAPPING (1 << JOBCTL_TRAPPING_BIT)
+#define JOBCTL_LISTENING (1 << JOBCTL_LISTENING_BIT)
#define JOBCTL_TRAP_MASK (JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)
#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)
diff --git a/kernel/exit.c b/kernel/exit.c
index 20a406471525..289f59d686bf 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1368,7 +1368,8 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
static int *task_stopped_code(struct task_struct *p, bool ptrace)
{
if (ptrace) {
- if (task_is_stopped_or_traced(p))
+ if (task_is_stopped_or_traced(p) &&
+ !(p->jobctl & JOBCTL_LISTENING))
return &p->exit_code;
} else {
if (p->signal->flags & SIGNAL_STOP_STOPPED)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 6852c0f4a916..e18966c1c0da 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -146,7 +146,8 @@ int ptrace_check_attach(struct task_struct *child, bool ignore_state)
*/
spin_lock_irq(&child->sighand->siglock);
WARN_ON_ONCE(task_is_stopped(child));
- if (task_is_traced(child) || ignore_state)
+ if (ignore_state || (task_is_traced(child) &&
+ !(child->jobctl & JOBCTL_LISTENING)))
ret = 0;
spin_unlock_irq(&child->sighand->siglock);
}
@@ -660,7 +661,7 @@ int ptrace_request(struct task_struct *child, long request,
{
bool seized = child->ptrace & PT_SEIZED;
int ret = -EIO;
- siginfo_t siginfo;
+ siginfo_t siginfo, *si;
void __user *datavp = (void __user *) data;
unsigned long __user *datalp = datavp;
unsigned long flags;
@@ -710,8 +711,43 @@ int ptrace_request(struct task_struct *child, long request,
if (unlikely(!seized || !lock_task_sighand(child, &flags)))
break;
+ /*
+ * INTERRUPT doesn't disturb existing trap sans one
+ * exception. If ptracer issued LISTEN for the current
+ * STOP, this INTERRUPT should clear LISTEN and re-trap
+ * tracee into STOP.
+ */
if (likely(task_set_jobctl_pending(child, JOBCTL_TRAP_STOP)))
- signal_wake_up(child, 0);
+ signal_wake_up(child, child->jobctl & JOBCTL_LISTENING);
+
+ unlock_task_sighand(child, &flags);
+ ret = 0;
+ break;
+
+ case PTRACE_LISTEN:
+ /*
+ * Listen for events. Tracee must be in STOP. It's not
+ * resumed per-se but is not considered to be in TRACED by
+ * wait(2) or ptrace(2). If an async event (e.g. group
+ * stop state change) happens, tracee will enter STOP trap
+ * again. Alternatively, ptracer can issue INTERRUPT to
+ * finish listening and re-trap tracee into STOP.
+ */
+ if (unlikely(!seized || !lock_task_sighand(child, &flags)))
+ break;
+
+ si = child->last_siginfo;
+ if (unlikely(!si || si->si_code >> 8 != PTRACE_EVENT_STOP))
+ break;
+
+ child->jobctl |= JOBCTL_LISTENING;
+
+ /*
+ * If NOTIFY is set, it means event happened between start
+ * of this trap and now. Trigger re-trap immediately.
+ */
+ if (child->jobctl & JOBCTL_TRAP_NOTIFY)
+ signal_wake_up(child, true);
unlock_task_sighand(child, &flags);
ret = 0;
diff --git a/kernel/signal.c b/kernel/signal.c
index 06177e2b3917..97e575a3387e 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -825,9 +825,11 @@ static int check_kill_permission(int sig, struct siginfo *info,
* TRAP_STOP to notify ptracer of an event. @t must have been seized by
* ptracer.
*
- * If @t is running, STOP trap will be taken. If already trapped, STOP
- * trap will be eventually taken without returning to userland after the
- * existing traps are finished by PTRACE_CONT.
+ * If @t is running, STOP trap will be taken. If trapped for STOP and
+ * ptracer is listening for events, tracee is woken up so that it can
+ * re-trap for the new event. If trapped otherwise, STOP trap will be
+ * eventually taken without returning to userland after the existing traps
+ * are finished by PTRACE_CONT.
*
* CONTEXT:
* Must be called with @task->sighand->siglock held.
@@ -838,7 +840,7 @@ static void ptrace_trap_notify(struct task_struct *t)
assert_spin_locked(&t->sighand->siglock);
task_set_jobctl_pending(t, JOBCTL_TRAP_NOTIFY);
- signal_wake_up(t, 0);
+ signal_wake_up(t, t->jobctl & JOBCTL_LISTENING);
}
/*
@@ -1894,6 +1896,9 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
spin_lock_irq(¤t->sighand->siglock);
current->last_siginfo = NULL;
+ /* LISTENING can be set only during STOP traps, clear it */
+ current->jobctl &= ~JOBCTL_LISTENING;
+
/*
* Queued signals ignored us while we were stopped for tracing.
* So check for any that we should take before resuming user mode.