kern: provide notifications about new tasks

These notifications are sent to the port registered via
`register_new_task_notification' and provide a robust parental
relation between tasks to a userspace server.

* Makefrag.am: Add task_notify.defs.
* include/mach/gnumach.defs: Add register_new_task_notification.
* include/mach/task_notify.defs: New file.
* kern/task.c (new_task_notification): New variable.
(task_create): Send new task notifications.
(register_new_task_notification): Add server function.
* kern/task_notify.cli: New file.

5 files changed, 92 insertions, 0 deletions

diff --git a/Makefrag.am b/Makefrag.am
index 5e98b219..410f56d6 100644
--- a/Makefrag.am
+++ b/Makefrag.am
@@ -364,6 +364,7 @@ include_mach_HEADERS = \
 	include/mach/mach.defs \
 	include/mach/mach4.defs \
 	include/mach/gnumach.defs \
+	include/mach/task_notify.defs \
 	include/mach/mach_host.defs \
 	include/mach/mach_port.defs \
 	include/mach/mach_types.defs \
@@ -488,6 +489,13 @@ nodist_libkernel_a_SOURCES += \
 #	device/device_reply.user.defs
 #	device/memory_object_reply.user.defs
 
+nodist_lib_dep_tr_for_defs_a_SOURCES += \
+	kern/task_notify.user.defs.c
+nodist_libkernel_a_SOURCES += \
+	kern/task_notify.user.h \
+	kern/task_notify.user.c \
+	kern/task_notify.user.msgids
+
 # Server stubs.
 nodist_lib_dep_tr_for_defs_a_SOURCES += \
 	device/device.server.defs.c \
diff --git a/include/mach/gnumach.defs b/include/mach/gnumach.defs
index 6cfbb0d0..bac3b097 100644
--- a/include/mach/gnumach.defs
+++ b/include/mach/gnumach.defs
@@ -72,3 +72,11 @@ simpleroutine thread_terminate_release(
 simpleroutine task_set_name(
 		task	: task_t;
 		name	: kernel_debug_name_t);
+
+/*
+ * Register a port to which a notification about newly created tasks
+ * are sent.
+ */
+routine register_new_task_notification(
+		host_priv	: host_priv_t;
+		notification	: mach_port_send_t);
diff --git a/include/mach/task_notify.defs b/include/mach/task_notify.defs
new file mode 100644
index 00000000..5485d4e3
--- /dev/null
+++ b/include/mach/task_notify.defs
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2014 Free Software Foundation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+subsystem
+#if	KERNEL_SERVER
+	  KernelServer
+#endif	/* KERNEL_SERVER */
+#if	KERNEL_USER
+	  KernelUser
+#endif	/* KERNEL_USER */
+		       task_notify 4400;
+
+#include <mach/std_types.defs>
+#include <mach/mach_types.defs>
+
+/* These notifications are sent to the port registered via
+   `register_new_task_notification' and provide a robust parental
+   relation between tasks.  */
+simpleroutine mach_notify_new_task(
+		notify	: mach_port_t;
+		task	: task_t;
+		parent	: task_t);
diff --git a/kern/task.c b/kern/task.c
index 44963c68..a11fb8ee 100644
--- a/kern/task.c
+++ b/kern/task.c
@@ -50,12 +50,16 @@
 #include <kern/sched_prim.h>	/* for thread_wakeup */
 #include <kern/ipc_tt.h>
 #include <kern/syscall_emulation.h>
+#include <kern/task_notify.user.h>
 #include <vm/vm_kern.h>		/* for kernel_map, ipc_kernel_map */
 #include <machine/machspl.h>	/* for splsched */
 
 task_t	kernel_task = TASK_NULL;
 struct kmem_cache task_cache;
 
+/* Where to send notifications about newly created tasks.  */
+ipc_port_t new_task_notification = NULL;
+
 void task_init(void)
 {
 	kmem_cache_init(&task_cache, "task", sizeof(struct task), 0,
@@ -169,6 +173,14 @@ kern_return_t task_create(
 
 	snprintf (new_task->name, sizeof new_task->name, "%p", new_task);
 
+	if (new_task_notification != NULL) {
+		task_reference (new_task);
+		task_reference (parent_task);
+		mach_notify_new_task (new_task_notification,
+				      convert_task_to_port (new_task),
+				      convert_task_to_port (parent_task));
+	}
+
 	ipc_task_enable(new_task);
 
 	*child_task = new_task;
@@ -1249,3 +1261,24 @@ task_ras_control(
 #endif /* FAST_TAS */
     return ret;
 }
+
+/*
+ *	register_new_task_notification
+ *
+ *	Register a port to which a notification about newly created
+ *	tasks are sent.
+ */
+kern_return_t
+register_new_task_notification(
+	const host_t host,
+	ipc_port_t notification)
+{
+	if (host == HOST_NULL)
+		return KERN_INVALID_HOST;
+
+	if (new_task_notification != NULL)
+		return KERN_NO_ACCESS;
+
+	new_task_notification = notification;
+	return KERN_SUCCESS;
+}
diff --git a/kern/task_notify.cli b/kern/task_notify.cli
new file mode 100644
index 00000000..c6c85d99
--- /dev/null
+++ b/kern/task_notify.cli
@@ -0,0 +1,7 @@
+/* XXX */
+
+/* This is a client presentation file.  */
+
+#define KERNEL_USER 1
+
+#include <mach/task_notify.defs>