/*
 * cn_proc.c - process events connector
 *
 * Copyright (C) Matt Helsley, IBM Corp. 2005
 * Based on cn_fork.c by Guillaume Thouvenin <guillaume.thouvenin@bull.net>
 * Original copyright notice follows:
 * Copyright (C) 2005 BULL SA.
 *
 *
 * 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/ktime.h>
#include <linux/init.h>
#include <linux/connector.h>
#include <linux/gfp.h>
#include <asm/atomic.h>
#include <asm/unaligned.h>

#include <linux/cn_proc.h>

#define CN_PROC_MSG_SIZE (sizeof(struct cn_msg) + sizeof(struct proc_event))

static atomic_t proc_event_num_listeners = ATOMIC_INIT(0);
static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC };

/* proc_event_counts is used as the sequence number of the netlink message */
static DEFINE_PER_CPU(__u32, proc_event_counts) = { 0 };

static inline void get_seq(__u32 *ts, int *cpu)
{
        preempt_disable();
        *ts = __this_cpu_inc_return(proc_event_counts) -1;
        *cpu = smp_processor_id();
        preempt_enable();
}

void proc_fork_connector(struct task_struct *task)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE];
        struct timespec ts;

        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_FORK;
        ev->event_data.fork.parent_pid = task->real_parent->pid;
        ev->event_data.fork.parent_tgid = task->real_parent->tgid;
        ev->event_data.fork.child_pid = task->pid;
        ev->event_data.fork.child_tgid = task->tgid;

        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = 0; /* not used */
        msg->len = sizeof(*ev);
        /*  If cn_netlink_send() failed, the data is not sent */
        cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
}

void proc_exec_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_EXEC;
        ev->event_data.exec.process_pid = task->pid;
        ev->event_data.exec.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_id_connector(struct task_struct *task, int which_id)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE];
        struct timespec ts;
        const struct cred *cred;

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = (struct cn_msg*)buffer;
        ev = (struct proc_event*)msg->data;
        ev->what = which_id;
        ev->event_data.id.process_pid = task->pid;
        ev->event_data.id.process_tgid = task->tgid;
        rcu_read_lock();
        cred = __task_cred(task);
        if (which_id == PROC_EVENT_UID) {
                ev->event_data.id.r.ruid = cred->uid;
                ev->event_data.id.e.euid = cred->euid;
        } else if (which_id == PROC_EVENT_GID) {
                ev->event_data.id.r.rgid = cred->gid;
                ev->event_data.id.e.egid = cred->egid;
        } else {
                rcu_read_unlock();
                return;
        }
        rcu_read_unlock();
        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);

        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_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;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE];
        struct timespec ts;

        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_EXIT;
        ev->event_data.exit.process_pid = task->pid;
        ev->event_data.exit.process_tgid = task->tgid;
        ev->event_data.exit.exit_code = task->exit_code;
        ev->event_data.exit.exit_signal = task->exit_signal;

        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);
}

/*
 * Send an acknowledgement message to userspace
 *
 * Use 0 for success, EFOO otherwise.
 * Note: this is the negative of conventional kernel error
 * values because it's not being returned via syscall return
 * mechanisms.
 */
static void cn_proc_ack(int err, int rcvd_seq, int rcvd_ack)
{
        struct cn_msg *msg;
        struct proc_event *ev;
        __u8 buffer[CN_PROC_MSG_SIZE];
        struct timespec ts;

        if (atomic_read(&proc_event_num_listeners) < 1)
                return;

        msg = (struct cn_msg*)buffer;
        ev = (struct proc_event*)msg->data;
        msg->seq = rcvd_seq;
        ktime_get_ts(&ts); /* get high res monotonic timestamp */
        put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);
        ev->cpu = -1;
        ev->what = PROC_EVENT_NONE;
        ev->event_data.ack.err = err;
        memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
        msg->ack = rcvd_ack + 1;
        msg->len = sizeof(*ev);
        cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
}

/**
 * cn_proc_mcast_ctl
 * @data: message sent from userspace via the connector
 */
static void cn_proc_mcast_ctl(struct cn_msg *msg,
                              struct netlink_skb_parms *nsp)
{
        enum proc_cn_mcast_op *mc_op = NULL;
        int err = 0;

        if (msg->len != sizeof(*mc_op))
                return;

        mc_op = (enum proc_cn_mcast_op*)msg->data;
        switch (*mc_op) {
        case PROC_CN_MCAST_LISTEN:
                atomic_inc(&proc_event_num_listeners);
                break;
        case PROC_CN_MCAST_IGNORE:
                atomic_dec(&proc_event_num_listeners);
                break;
        default:
                err = EINVAL;
                break;
        }
        cn_proc_ack(err, msg->seq, msg->ack);
}

/*
 * cn_proc_init - initialization entry point
 *
 * Adds the connector callback to the connector driver.
 */
static int __init cn_proc_init(void)
{
        int err;

        if ((err = cn_add_callback(&cn_proc_event_id, "cn_proc",
                                   &cn_proc_mcast_ctl))) {
                printk(KERN_WARNING "cn_proc failed to register\n");
                return err;
        }
        return 0;
}

module_init(cn_proc_init);