> Index: linux-2.6.12-rc3-mm3/drivers/connector/cn_fork.c
> ===================================================================
> --- linux-2.6.12-rc3-mm3.orig/drivers/connector/cn_fork.c 2003-01-30 11:24:37.000000000 +0100
> +++ linux-2.6.12-rc3-mm3/drivers/connector/cn_fork.c 2005-05-09 14:36:22.000000000 +0200
> @@ -0,0 +1,132 @@
> +/*
> + * cn_fork.c - Fork connector
> + *
> + * Copyright (C) 2005 BULL SA.
> + * Written by Guillaume Thouvenin <[email protected]>
> + *
> + * This module implements the fork connector. It allows to send a
> + * netlink datagram, when enabled, from the do_fork() routine. The
> + * message can be read by a user space application. By this way,
> + * the user space application is alerted when a fork occurs.
> + *
> + * It uses the userspace <-> kernelspace connector that works on top of
> + * the netlink protocol. The fork connector is enabled or disabled by
> + * sending a message to the connector. The unique sequence number of
> + * messages can be used to check if a message is lost.
> + *
> + * 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, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +
> +#include <linux/cn_fork.h>
> +
> +#define CN_FORK_INFO_SIZE sizeof(struct cn_fork_msg)
> +#define CN_FORK_MSG_SIZE (sizeof(struct cn_msg) + CN_FORK_INFO_SIZE)
> +
> +static int cn_fork_enable = 0;
> +struct cb_id cb_fork_id = { CN_IDX_FORK, CN_VAL_FORK };
> +
> +/* fork_counts is used as the sequence number of the netlink message */
> +static DEFINE_PER_CPU(unsigned long, fork_counts);
> +
> +void fork_connector(pid_t thread, pid_t parent, pid_t child)
> +{
> + if (cn_fork_enable) {
> + struct cn_msg *msg;
> + struct cn_fork_msg *forkmsg;
> + __u8 buffer[CN_FORK_MSG_SIZE];
> +
> + msg = (struct cn_msg *)buffer;
> +
> + memcpy(&msg->id, &cb_fork_id, sizeof(msg->id));
> +
> + msg->ack = 0; /* not used */
> + msg->seq = get_cpu_var(fork_counts)++;
> +
> + msg->len = CN_FORK_INFO_SIZE;
> + forkmsg = (struct cn_fork_msg *)msg->data;
> + forkmsg->cpu = smp_processor_id();
> + forkmsg->tgid = thread;
> + forkmsg->ppid = parent;
> + forkmsg->cpid = child;
> +
> + put_cpu_var(fork_counts);
> +
> + cn_netlink_send(msg, CN_IDX_FORK, GFP_KERNEL|__GFP_NOFAIL);
> + }
> +}
> +EXPORT_SYMBOL_GPL(fork_connector);
the export symbol police will get you for this, any intended users?
> +
> +static inline void cn_fork_send_status(void)
> +{
> + /* TODO: An informational line in log is maybe not enough... */
> + printk(KERN_INFO "cn_fork_enable == %d\n", cn_fork_enable);
> +}
> +
> +/**
> + * cn_fork_callback - enable or disable the fork connector
> + * @data: message send by the connector
> + *
> + * The callback allows to enable or disable the sending of information
> + * about fork in the do_fork() routine. To enable the fork, the user
> + * space application must send the integer 1 in the data part of the
> + * message. To disable the fork connector, it must send the integer 0.
> + */
> +static void cn_fork_callback(void *data)
> +{
> + struct cn_msg *msg = data;
> + int action;
> +
> + if (cn_already_initialized && (msg->len == sizeof(cn_fork_enable))) {
> + memcpy(&action, msg->data, sizeof(cn_fork_enable));
> + switch(action) {
> + case FORK_CN_START:
> + cn_fork_enable = 1;
> + break;
> + case FORK_CN_STOP:
> + cn_fork_enable = 0;
> + break;
> + case FORK_CN_STATUS:
> + cn_fork_send_status();
Why does this not pass down the status to the app asking about it
instead?
> + break;
> + }
> + }
> +}
> +
> +/**
> + * cn_fork_init - initialization entry point
> + *
> + * This routine will be run at kernel boot time because this driver is
> + * built in the kernel. It adds the connector callback to the connector
> + * driver.
> + */
> +int __init cn_fork_init(void)
> +{
> + int err;
> +
> + err = cn_add_callback(&cb_fork_id, "cn_fork", &cn_fork_callback);
> + if (err) {
> + printk(KERN_WARNING "Failed to register cn_fork\n");
> + return -EINVAL;
> + }
> +
> + printk(KERN_NOTICE "cn_fork is registered\n");
> + return 0;
> +}
> +
> +__initcall(cn_fork_init);
> Index: linux-2.6.12-rc3-mm3/include/linux/cn_fork.h
> ===================================================================
> --- linux-2.6.12-rc3-mm3.orig/include/linux/cn_fork.h 2003-01-30 11:24:37.000000000 +0100
> +++ linux-2.6.12-rc3-mm3/include/linux/cn_fork.h 2005-05-09 14:34:36.000000000 +0200
> @@ -0,0 +1,54 @@
> +/*
> + * cn_fork.h - Fork connector
> + *
> + * Copyright (C) 2005 Nguyen Anh Quynh <[email protected]>
> + * Copyright (C) 2005 Guillaume Thouvenin <[email protected]>
> + *
> + * 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, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> + */
> +
> +#ifndef CN_FORK_H
> +#define CN_FORK_H
> +
> +#include <linux/connector.h>
> +
> +#define FORK_CN_STOP 0
> +#define FORK_CN_START 1
> +#define FORK_CN_STATUS 2
> +
> +struct cn_fork_msg
> +{
> + int cpu; /* ID of the cpu where the fork occured */
> + pid_t tgid; /* thread leader PID */
> + pid_t ppid; /* the parent PID */
> + pid_t cpid; /* the child PID */
> +};
> +
What I meant here was something like:
struct cn_fork_msg {
int cpu;
pid_t ppid; /* parent process id */
pid_t ptid; /* parent thread id */
pid_t cpid; /* child process id */
pid_t ctid; /* child thread id */
};
Now if cpid == ctid it is a group leader but you cannot know this
otherwise. I don't know if you specifically need this but there may be
other users, and this is more complete. If not you may receive multiple
messages with the same child pid. Again I don't know how much you care.
As this is shared with user-space the fields need to switched like this:
ppid = current->tgid,
ptid = current->pid,
cpid = p->tgid,
ctid = current->pid
and perhaps a comment to explain why we assign the fields like this.
Please think through what you need to pass down to user-space, it's
important.
> +/* Code above is only inside the kernel */
> +#ifdef __KERNEL__
> +
> +extern int cn_already_initialized;
this should go into linux/connector.h
> +#ifdef CONFIG_FORK_CONNECTOR
> +extern void fork_connector(pid_t, pid_t, pid_t);
> +#else
> +static inline void fork_connector(pid_t thread, pid_t parent, pid_t child)
> +{
> + return;
> +}
> +#endif /* CONFIG_FORK_CONNECTOR */
> +
> +#endif /* __KERNEL__ */
> +#endif /* CN_FORK_H */
> Index: linux-2.6.12-rc3-mm3/include/linux/connector.h
> ===================================================================
> --- linux-2.6.12-rc3-mm3.orig/include/linux/connector.h 2005-05-09 07:45:56.000000000 +0200
> +++ linux-2.6.12-rc3-mm3/include/linux/connector.h 2005-05-09 09:50:01.000000000 +0200
> @@ -26,6 +26,8 @@
>
> #define CN_IDX_CONNECTOR 0xffffffff
> #define CN_VAL_CONNECTOR 0xffffffff
> +#define CN_IDX_FORK 0xfeed /* fork events */
> +#define CN_VAL_FORK 0xbeef
>
> /*
> * Maximum connector's message size.
> Index: linux-2.6.12-rc3-mm3/kernel/fork.c
> ===================================================================
> --- linux-2.6.12-rc3-mm3.orig/kernel/fork.c 2005-05-09 07:45:56.000000000 +0200
> +++ linux-2.6.12-rc3-mm3/kernel/fork.c 2005-05-09 14:23:04.000000000 +0200
> @@ -41,6 +41,7 @@
> #include <linux/profile.h>
> #include <linux/rmap.h>
> #include <linux/acct.h>
> +#include <linux/cn_fork.h>
>
> #include <asm/pgtable.h>
> #include <asm/pgalloc.h>
> @@ -1252,6 +1253,8 @@ 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->tgid, current->pid, p->pid);
With your current implementation this is wrong, first two args should
switched, third arg should be p->tgid. The differences between kernel
and user pid must be hidden as you share struct cn_fork_msg with
user-space.
> } else {
> free_pidmap(pid);
> pid = PTR_ERR(p);
>
>
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