[PATCH 2.6.11-rc3-mm2] connector: Add a fork connector

[Guillaume Thouvenin]

Hello,

    It's a new patch that implements a fork connector in the
kernel/fork.c:do_fork() routine. The connector sends information about
parent PID and child PID over a netlink interface. It allows to several
user space applications to be alerted when a fork occurs in the kernel.
The main drawback is that even if nobody listens, a message is send. I
don't know how to avoid that. I added an option (FORK_CONNECTOR) to
enable the fork connector (or disable) when compiling the kernel. To
work, connector must be compiled as built-in (CONFIG_CONNECTOR=y). It
has been tested on a 2.6.11-rc3-mm2 kernel with two user space
applications connected. 

    It is used by ELSA to manage group of processes in user space. In
conjunction with a per-process accounting information, like BSD or CSA,
ELSA provides a per-group of processes accounting.


    Every comments are welcome,

Guillaume

Signed-off-by: Guillaume Thouvenin <guillaume.thouvenin@xxxxxxxx>
--- 

 drivers/connector/Kconfig |   10 ++++++++++
 include/linux/connector.h |    2 ++
 kernel/fork.c             |   41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff -uprN -X dontdiff linux-2.6.11-rc3-mm2/drivers/connector/Kconfig linux-2.6.11-rc3-mm2-cnfork/drivers/connector/Kconfig
--- linux-2.6.11-rc3-mm2/drivers/connector/Kconfig	2005-02-11 11:00:16.000000000 +0100
+++ linux-2.6.11-rc3-mm2-cnfork/drivers/connector/Kconfig	2005-02-17 15:48:41.000000000 +0100
@@ -10,4 +10,14 @@ config CONNECTOR
 	  Connector support can also be built as a module.  If so, the module
 	  will be called cn.ko.
 
+config FORK_CONNECTOR
+	bool "Enable fork connector"
+	depends on CONNECTOR
+	---help---
+	  It adds a connector in kernel/fork.c:do_fork() function. When a fork
+	  occurs, netlink is used to transfer information about the parent and 
+	  its child. This information can be used by a user space application. 
+	  
+	  Note: it only works if connector is built in the kernel.
+	  
 endmenu
diff -uprN -X dontdiff linux-2.6.11-rc3-mm2/include/linux/connector.h linux-2.6.11-rc3-mm2-cnfork/include/linux/connector.h
--- linux-2.6.11-rc3-mm2/include/linux/connector.h	2005-02-11 11:00:18.000000000 +0100
+++ linux-2.6.11-rc3-mm2-cnfork/include/linux/connector.h	2005-02-16 15:07:46.000000000 +0100
@@ -28,6 +28,8 @@
 #define CN_VAL_KOBJECT_UEVENT		0x0000
 #define CN_IDX_SUPERIO			0xaabb  /* SuperIO subsystem */
 #define CN_VAL_SUPERIO			0xccdd
+#define CN_IDX_FORK			0xfeed  /* fork events */
+#define CN_VAL_FORK			0xbeef
 
 
 #define CONNECTOR_MAX_MSG_SIZE 	1024
diff -uprN -X dontdiff linux-2.6.11-rc3-mm2/kernel/fork.c linux-2.6.11-rc3-mm2-cnfork/kernel/fork.c
--- linux-2.6.11-rc3-mm2/kernel/fork.c	2005-02-11 11:00:18.000000000 +0100
+++ linux-2.6.11-rc3-mm2-cnfork/kernel/fork.c	2005-02-17 13:43:48.000000000 +0100
@@ -41,6 +41,7 @@
 #include <linux/profile.h>
 #include <linux/rmap.h>
 #include <linux/acct.h>
+#include <linux/connector.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -63,6 +64,44 @@ DEFINE_PER_CPU(unsigned long, process_co
 
 EXPORT_SYMBOL(tasklist_lock);
 
+#if defined(CONFIG_CONNECTOR) && defined(CONFIG_FORK_CONNECTOR)
+#define FORK_CN_INFO_SIZE	64 
+static inline void fork_connector(pid_t parent, pid_t child)
+{
+	struct cb_id fork_id = {CN_IDX_FORK, CN_VAL_FORK};
+	static __u32 seq; /* used to test if we lost message */
+	
+	if (cn_already_initialized) {
+		struct cn_msg *msg;
+		size_t size;
+
+		size = sizeof(*msg) + FORK_CN_INFO_SIZE;
+		msg = kmalloc(size, GFP_KERNEL);
+		if (msg) {
+			memset(msg, '\0', size);
+			memcpy(&msg->id, &fork_id, sizeof(msg->id));
+			msg->seq = seq++;
+			msg->ack = 0; /* not used */
+			/* 
+			 * size of data is the number of characters 
+			 * printed plus one for the trailing '\0'
+			 */
+			msg->len = snprintf(msg->data, FORK_CN_INFO_SIZE-1, 
+					    "%i %i", parent, child) + 1;
+
+			cn_netlink_send(msg, 1);
+
+			kfree(msg);
+		}
+	}
+}
+#else
+static inline void fork_connector(pid_t parent, pid_t child) 
+{
+	return; 
+}
+#endif
+
 int nr_processes(void)
 {
 	int cpu;
@@ -1238,6 +1277,8 @@ long do_fork(unsigned long clone_flags,
 			if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
 				ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
 		}
+
+		fork_connector(current->pid, p->pid);
 	} else {
 		free_pidmap(pid);
 		pid = PTR_ERR(p);


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/