ptrace: kill trivial tracehooks

At this point, tracehooks aren't useful to mainline kernel and mostly
just add an extra layer of obfuscation.  Although they have comments,
without actual in-kernel users, it is difficult to tell what are their
assumptions and they're actually trying to achieve.  To mainline
kernel, they just aren't worth keeping around.

This patch kills the following trivial tracehooks.

* Ones testing whether task is ptraced.  Replace with ->ptrace test.

	tracehook_expect_breakpoints()
	tracehook_consider_ignored_signal()
	tracehook_consider_fatal_signal()

* ptrace_event() wrappers.  Call directly.

	tracehook_report_exec()
	tracehook_report_exit()
	tracehook_report_vfork_done()

* ptrace_release_task() wrapper.  Call directly.

	tracehook_finish_release_task()

* noop

	tracehook_prepare_release_task()
	tracehook_report_death()

This doesn't introduce any behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>

3 files changed, 7 insertions, 10 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index e5cc056..d49134a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -169,7 +169,6 @@ void release_task(struct task_struct * p)
 	struct task_struct *leader;
 	int zap_leader;
 repeat:
-	tracehook_prepare_release_task(p);
 	/* don't need to get the RCU readlock here - the process is dead and
 	 * can't be modifying its own credentials. But shut RCU-lockdep up */
 	rcu_read_lock();
@@ -179,7 +178,7 @@ repeat:
 	proc_flush_task(p);
 
 	write_lock_irq(&tasklist_lock);
-	tracehook_finish_release_task(p);
+	ptrace_release_task(p);
 	__exit_signal(p);
 
 	/*
@@ -868,8 +867,6 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
 		wake_up_process(tsk->signal->group_exit_task);
 	write_unlock_irq(&tasklist_lock);
 
-	tracehook_report_death(tsk, signal, cookie, group_dead);
-
 	/* If the process is dead, release it - nobody will wait for it */
 	if (signal == DEATH_REAP)
 		release_task(tsk);
@@ -924,7 +921,7 @@ NORET_TYPE void do_exit(long code)
 	 */
 	set_fs(USER_DS);
 
-	tracehook_report_exit(&code);
+	ptrace_event(PTRACE_EVENT_EXIT, code);
 
 	validate_creds_for_do_exit(tsk);
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 0276c30..d4f0dff 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1527,7 +1527,7 @@ long do_fork(unsigned long clone_flags,
 			freezer_do_not_count();
 			wait_for_completion(&vfork);
 			freezer_count();
-			tracehook_report_vfork_done(p, nr);
+			ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
 		}
 	} else {
 		nr = PTR_ERR(p);
diff --git a/kernel/signal.c b/kernel/signal.c
index 0f33708..1550aee 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -87,7 +87,7 @@ static int sig_ignored(struct task_struct *t, int sig, int from_ancestor_ns)
 	/*
 	 * Tracers may want to know about even ignored signals.
 	 */
-	return !tracehook_consider_ignored_signal(t, sig);
+	return !t->ptrace;
 }
 
 /*
@@ -493,7 +493,8 @@ int unhandled_signal(struct task_struct *tsk, int sig)
 		return 1;
 	if (handler != SIG_IGN && handler != SIG_DFL)
 		return 0;
-	return !tracehook_consider_fatal_signal(tsk, sig);
+	/* if ptraced, let the tracer determine */
+	return !tsk->ptrace;
 }
 
 /*
@@ -981,8 +982,7 @@ static void complete_signal(int sig, struct task_struct *p, int group)
 	if (sig_fatal(p, sig) &&
 	    !(signal->flags & (SIGNAL_UNKILLABLE | SIGNAL_GROUP_EXIT)) &&
 	    !sigismember(&t->real_blocked, sig) &&
-	    (sig == SIGKILL ||
-	     !tracehook_consider_fatal_signal(t, sig))) {
+	    (sig == SIGKILL || !t->ptrace)) {
 		/*
 		 * This signal will be fatal to the whole group.
 		 */