connector: add comm change event report to proc connector

Add an event to monitor comm value changes of tasks.  Such an event
becomes vital, if someone desires to control threads of a process in
different manner.

A natural characteristic of threads is its comm value, and helpfully
application developers have an opportunity to change it in runtime.
Reporting about such events via proc connector allows to fine-grain
monitoring and control potentials, for instance a process control daemon
listening to proc connector and following comm value policies can place
specific threads to assigned cgroup partitions.

It might be possible to achieve a pale partial one-shot likeness without
this update, if an application changes comm value of a thread generator
task beforehand, then a new thread is cloned, and after that proc
connector listener gets the fork event and reads new thread's comm value
from procfs stat file, but this change visibly simplifies and extends the
matter.

Signed-off-by: Vladimir Zapolskiy <vzapolskiy@gmail.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index e55814bc0d06..77e1e6cd66ce 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -205,6 +205,32 @@ void proc_ptrace_connector(struct task_struct *task, int ptrace_id)
         cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
 }
 
+void proc_comm_connector(struct task_struct *task)
+{
+        struct cn_msg *msg;
+        struct proc_event *ev;
+        struct timespec ts;
+        __u8 buffer[CN_PROC_MSG_SIZE];
+
+        if (atomic_read(&proc_event_num_listeners) < 1)
+                return;
+
+        msg = (struct cn_msg *)buffer;
+        ev = (struct proc_event *)msg->data;
+        get_seq(&msg->seq, &ev->cpu);
+        ktime_get_ts(&ts); /* get high res monotonic timestamp */
+        put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);
+        ev->what = PROC_EVENT_COMM;
+        ev->event_data.comm.process_pid  = task->pid;
+        ev->event_data.comm.process_tgid = task->tgid;
+        get_task_comm(ev->event_data.comm.comm, task);
+
+        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
+        msg->ack = 0; /* not used */
+        msg->len = sizeof(*ev);
+        cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
+}
+
 void proc_exit_connector(struct task_struct *task)
 {
         struct cn_msg *msg;