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Date: Mon, 15 Jun 2009 13:03:08 +0100
From: Scott James Remnant <scott@...ntu.com>
To: linux-kernel@...r.kernel.org
Subject: [PATCH] proc connector: add event for process becoming session leader
The act of a process becoming a session leader is a useful signal to a
supervising init daemon such as Upstart.
While a daemon will normally do this as part of the process of becoming
a daemon, it is rare for its children to do so. When the children do,
it is nearly always a sign that the child should be considered detached
from the parent and not supervised along with it.
The poster-child example is OpenSSH; the per-login children call setsid()
so that they may control the pty connected to them. If the primary daemon
dies or is restarted, we do not want to consider the per-login children
and want to respawn the primary daemon without killing the children.
This patch adds a new PROC_SID_EVENT and associated structure to the
proc_event event_data union, it arranges for this to be emitted when
the special PIDTYPE_SID pid is set.
Signed-off-by: Scott James Remnant <scott@...ntu.com>
---
drivers/connector/cn_proc.c | 25 +++++++++++++++++++++++++
include/linux/cn_proc.h | 10 ++++++++++
kernel/exit.c | 4 +++-
3 files changed, 38 insertions(+), 1 deletions(-)
diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index c5afc98..7d48cd9 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -139,6 +139,31 @@ void proc_id_connector(struct task_struct *task, int which_id)
cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
}
+void proc_sid_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_SID;
+ ev->event_data.sid.process_pid = task->pid;
+ ev->event_data.sid.process_tgid = task->tgid;
+
+ 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;
diff --git a/include/linux/cn_proc.h b/include/linux/cn_proc.h
index b8125b2..47dac5e 100644
--- a/include/linux/cn_proc.h
+++ b/include/linux/cn_proc.h
@@ -52,6 +52,7 @@ struct proc_event {
PROC_EVENT_EXEC = 0x00000002,
PROC_EVENT_UID = 0x00000004,
PROC_EVENT_GID = 0x00000040,
+ PROC_EVENT_SID = 0x00000080,
/* "next" should be 0x00000400 */
/* "last" is the last process event: exit */
PROC_EVENT_EXIT = 0x80000000
@@ -89,6 +90,11 @@ struct proc_event {
} e;
} id;
+ struct sid_proc_event {
+ __kernel_pid_t process_pid;
+ __kernel_pid_t process_tgid;
+ } sid;
+
struct exit_proc_event {
__kernel_pid_t process_pid;
__kernel_pid_t process_tgid;
@@ -102,6 +108,7 @@ struct proc_event {
void proc_fork_connector(struct task_struct *task);
void proc_exec_connector(struct task_struct *task);
void proc_id_connector(struct task_struct *task, int which_id);
+void proc_sid_connector(struct task_struct *task);
void proc_exit_connector(struct task_struct *task);
#else
static inline void proc_fork_connector(struct task_struct *task)
@@ -114,6 +121,9 @@ static inline void proc_id_connector(struct task_struct *task,
int which_id)
{}
+static inline void proc_sid_connector(struct task_struct *task)
+{}
+
static inline void proc_exit_connector(struct task_struct *task)
{}
#endif /* CONFIG_PROC_EVENTS */
diff --git a/kernel/exit.c b/kernel/exit.c
index b6c90b5..5162589 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -360,8 +360,10 @@ void __set_special_pids(struct pid *pid)
{
struct task_struct *curr = current->group_leader;
- if (task_session(curr) != pid)
+ if (task_session(curr) != pid) {
change_pid(curr, PIDTYPE_SID, pid);
+ proc_sid_connector(curr);
+ }
if (task_pgrp(curr) != pid)
change_pid(curr, PIDTYPE_PGID, pid);
--
1.6.0.5
--
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