[RFC PATCH 1/1] netlink: Add Netlink process event for cgroup migration

[Prakash Sangappa]

Introduce a netlink process event that gets generated
when a task migrates between cgroup. The process event
includes the task's pid,tgid and the initiator process
pid,tgid along with the destination cgroup id.

Signed-off-by: Prakash Sangappa <prakash.sangappa@xxxxxxxxxx>
---
 drivers/connector/cn_proc.c  | 28 ++++++++++++++++++++++++++++
 include/linux/cn_proc.h      |  3 +++
 include/uapi/linux/cn_proc.h | 14 ++++++++++++--
 kernel/cgroup/cgroup-v1.c    |  7 ++++++-
 kernel/cgroup/cgroup.c       |  5 ++++-
 5 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index 0056ab81fbc3..4a17572ae171 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -19,6 +19,7 @@
 
 #include <linux/cn_proc.h>
 #include <linux/local_lock.h>
+#include <linux/cgroup.h>
 
 /*
  * Size of a cn_msg followed by a proc_event structure.  Since the
@@ -355,6 +356,33 @@ void proc_exit_connector(struct task_struct *task)
 	send_msg(msg);
 }
 
+void proc_cgroup_migrate_connector(struct task_struct *task, struct cgroup *cgrp)
+{
+	struct cn_msg *msg;
+	struct proc_event *ev;
+	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
+
+	if (atomic_read(&proc_event_num_listeners) < 1)
+		return;
+
+	msg = buffer_to_cn_msg(buffer);
+	ev = (struct proc_event *)msg->data;
+	memset(&ev->event_data, 0, sizeof(ev->event_data));
+	ev->timestamp_ns = ktime_get_ns();
+	ev->what = PROC_EVENT_CGRP_MIGRATE;
+	ev->event_data.cgrp.process_pid = task->pid;
+	ev->event_data.cgrp.process_tgid = task->tgid;
+	ev->event_data.cgrp.initiator_pid = current->pid;
+	ev->event_data.cgrp.initiator_tgid = current->tgid;
+	ev->event_data.cgrp.cgroup_id = cgroup_id(cgrp);
+
+	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
+	msg->ack = 0; /* not used */
+	msg->len = sizeof(*ev);
+	msg->flags = 0; /* not used */
+	send_msg(msg);
+}
+
 /*
  * Send an acknowledgement message to userspace
  *
diff --git a/include/linux/cn_proc.h b/include/linux/cn_proc.h
index 1d5b02a96c46..9b16a0456af6 100644
--- a/include/linux/cn_proc.h
+++ b/include/linux/cn_proc.h
@@ -28,6 +28,7 @@ void proc_ptrace_connector(struct task_struct *task, int which_id);
 void proc_comm_connector(struct task_struct *task);
 void proc_coredump_connector(struct task_struct *task);
 void proc_exit_connector(struct task_struct *task);
+void proc_cgroup_migrate_connector(struct task_struct *task, struct cgroup *cgrp);
 #else
 static inline void proc_fork_connector(struct task_struct *task)
 {}
@@ -54,5 +55,7 @@ static inline void proc_coredump_connector(struct task_struct *task)
 
 static inline void proc_exit_connector(struct task_struct *task)
 {}
+static inline void proc_cgrp_migrate_connector(struct task_struct *task)
+{}
 #endif	/* CONFIG_PROC_EVENTS */
 #endif	/* CN_PROC_H */
diff --git a/include/uapi/linux/cn_proc.h b/include/uapi/linux/cn_proc.h
index 18e3745b86cd..c202d7fdab28 100644
--- a/include/uapi/linux/cn_proc.h
+++ b/include/uapi/linux/cn_proc.h
@@ -33,7 +33,8 @@ enum proc_cn_mcast_op {
 #define PROC_EVENT_ALL (PROC_EVENT_FORK | PROC_EVENT_EXEC | PROC_EVENT_UID |  \
 			PROC_EVENT_GID | PROC_EVENT_SID | PROC_EVENT_PTRACE | \
 			PROC_EVENT_COMM | PROC_EVENT_NONZERO_EXIT |           \
-			PROC_EVENT_COREDUMP | PROC_EVENT_EXIT)
+			PROC_EVENT_COREDUMP | PROC_EVENT_EXIT | \
+			PROC_EVENT_CGRP_MIGRATE)
 
 /*
  * If you add an entry in proc_cn_event, make sure you add it in
@@ -51,7 +52,8 @@ enum proc_cn_event {
 	PROC_EVENT_SID  = 0x00000080,
 	PROC_EVENT_PTRACE = 0x00000100,
 	PROC_EVENT_COMM = 0x00000200,
-	/* "next" should be 0x00000400 */
+	PROC_EVENT_CGRP_MIGRATE = 0x00000400,
+	/* "next" should be 0x00000800 */
 	/* "last" is the last process event: exit,
 	 * while "next to last" is coredumping event
 	 * before that is report only if process dies
@@ -153,6 +155,14 @@ struct proc_event {
 			__kernel_pid_t parent_tgid;
 		} exit;
 
+		struct cgrp_proc_event {
+			__kernel_pid_t process_pid;
+			__kernel_pid_t process_tgid;
+			__kernel_pid_t initiator_pid;
+			__kernel_pid_t initiator_tgid;
+			__u64          cgroup_id;
+		} cgrp;
+
 	} event_data;
 };
 
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index a4337c9b5287..9b07c9ad9b43 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -16,6 +16,8 @@
 #include <linux/pid_namespace.h>
 #include <linux/cgroupstats.h>
 #include <linux/fs_parser.h>
+#include <linux/cn_proc.h>
+
 
 #include <trace/events/cgroup.h>
 
@@ -147,8 +149,11 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
 
 		if (task) {
 			ret = cgroup_migrate(task, false, &mgctx);
-			if (!ret)
+			if (!ret) {
+				proc_cgroup_migrate_connector(task, to);
 				TRACE_CGROUP_PATH(transfer_tasks, to, task, false);
+			}
+
 			put_task_struct(task);
 		}
 	} while (task && !ret);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 01fc2a93f3ef..4cac29d5c1b5 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -59,6 +59,7 @@
 #include <linux/nstree.h>
 #include <linux/irq_work.h>
 #include <net/sock.h>
+#include <linux/cn_proc.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/cgroup.h>
@@ -3040,8 +3041,10 @@ int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
 
 	cgroup_migrate_finish(&mgctx);
 
-	if (!ret)
+	if (!ret) {
+		proc_cgroup_migrate_connector(leader, dst_cgrp);
 		TRACE_CGROUP_PATH(attach_task, dst_cgrp, leader, threadgroup);
+	}
 
 	return ret;
 }
-- 
2.43.7