Linux 6.13

[linux.git] / drivers / net / netconsole.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  linux/drivers/net/netconsole.c
 *
 *  Copyright (C) 2001  Ingo Molnar <mingo@redhat.com>
 *
 *  This file contains the implementation of an IRQ-safe, crash-safe
 *  kernel console implementation that outputs kernel messages to the
 *  network.
 *
 * Modification history:
 *
 * 2001-09-17    started by Ingo Molnar.
 * 2003-08-11    2.6 port by Matt Mackall
 *               simplified options
 *               generic card hooks
 *               works non-modular
 * 2003-09-07    rewritten with netpoll api
 */

/****************************************************************
 *
 ****************************************************************/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/mm.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/console.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/netpoll.h>
#include <linux/inet.h>
#include <linux/configfs.h>
#include <linux/etherdevice.h>
#include <linux/utsname.h>
#include <linux/rtnetlink.h>

MODULE_AUTHOR("Matt Mackall <mpm@selenic.com>");
MODULE_DESCRIPTION("Console driver for network interfaces");
MODULE_LICENSE("GPL");

#define MAX_PARAM_LENGTH                256
#define MAX_USERDATA_ENTRY_LENGTH       256
#define MAX_USERDATA_VALUE_LENGTH       200
/* The number 3 comes from userdata entry format characters (' ', '=', '\n') */
#define MAX_USERDATA_NAME_LENGTH        (MAX_USERDATA_ENTRY_LENGTH - \
                                        MAX_USERDATA_VALUE_LENGTH - 3)
#define MAX_USERDATA_ITEMS              16
#define MAX_PRINT_CHUNK                 1000

static char config[MAX_PARAM_LENGTH];
module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0);
MODULE_PARM_DESC(netconsole, " netconsole=[src-port]@[src-ip]/[dev],[tgt-port]@<tgt-ip>/[tgt-macaddr]");

static bool oops_only;
module_param(oops_only, bool, 0600);
MODULE_PARM_DESC(oops_only, "Only log oops messages");

#define NETCONSOLE_PARAM_TARGET_PREFIX "cmdline"

#ifndef MODULE
static int __init option_setup(char *opt)
{
        strscpy(config, opt, MAX_PARAM_LENGTH);
        return 1;
}
__setup("netconsole=", option_setup);
#endif  /* MODULE */

/* Linked list of all configured targets */
static LIST_HEAD(target_list);
/* target_cleanup_list is used to track targets that need to be cleaned outside
 * of target_list_lock. It should be cleaned in the same function it is
 * populated.
 */
static LIST_HEAD(target_cleanup_list);

/* This needs to be a spinlock because write_msg() cannot sleep */
static DEFINE_SPINLOCK(target_list_lock);
/* This needs to be a mutex because netpoll_cleanup might sleep */
static DEFINE_MUTEX(target_cleanup_list_lock);

/*
 * Console driver for extended netconsoles.  Registered on the first use to
 * avoid unnecessarily enabling ext message formatting.
 */
static struct console netconsole_ext;

/**
 * struct netconsole_target - Represents a configured netconsole target.
 * @list:       Links this target into the target_list.
 * @group:      Links us into the configfs subsystem hierarchy.
 * @userdata_group:     Links to the userdata configfs hierarchy
 * @userdata_complete:  Cached, formatted string of append
 * @userdata_length:    String length of userdata_complete
 * @enabled:    On / off knob to enable / disable target.
 *              Visible from userspace (read-write).
 *              We maintain a strict 1:1 correspondence between this and
 *              whether the corresponding netpoll is active or inactive.
 *              Also, other parameters of a target may be modified at
 *              runtime only when it is disabled (enabled == 0).
 * @extended:   Denotes whether console is extended or not.
 * @release:    Denotes whether kernel release version should be prepended
 *              to the message. Depends on extended console.
 * @np:         The netpoll structure for this target.
 *              Contains the other userspace visible parameters:
 *              dev_name        (read-write)
 *              local_port      (read-write)
 *              remote_port     (read-write)
 *              local_ip        (read-write)
 *              remote_ip       (read-write)
 *              local_mac       (read-only)
 *              remote_mac      (read-write)
 */
struct netconsole_target {
        struct list_head        list;
#ifdef  CONFIG_NETCONSOLE_DYNAMIC
        struct config_group     group;
        struct config_group     userdata_group;
        char userdata_complete[MAX_USERDATA_ENTRY_LENGTH * MAX_USERDATA_ITEMS];
        size_t                  userdata_length;
#endif
        bool                    enabled;
        bool                    extended;
        bool                    release;
        struct netpoll          np;
};

#ifdef  CONFIG_NETCONSOLE_DYNAMIC

static struct configfs_subsystem netconsole_subsys;
static DEFINE_MUTEX(dynamic_netconsole_mutex);

static int __init dynamic_netconsole_init(void)
{
        config_group_init(&netconsole_subsys.su_group);
        mutex_init(&netconsole_subsys.su_mutex);
        return configfs_register_subsystem(&netconsole_subsys);
}

static void __exit dynamic_netconsole_exit(void)
{
        configfs_unregister_subsystem(&netconsole_subsys);
}

/*
 * Targets that were created by parsing the boot/module option string
 * do not exist in the configfs hierarchy (and have NULL names) and will
 * never go away, so make these a no-op for them.
 */
static void netconsole_target_get(struct netconsole_target *nt)
{
        if (config_item_name(&nt->group.cg_item))
                config_group_get(&nt->group);
}

static void netconsole_target_put(struct netconsole_target *nt)
{
        if (config_item_name(&nt->group.cg_item))
                config_group_put(&nt->group);
}

#else   /* !CONFIG_NETCONSOLE_DYNAMIC */

static int __init dynamic_netconsole_init(void)
{
        return 0;
}

static void __exit dynamic_netconsole_exit(void)
{
}

/*
 * No danger of targets going away from under us when dynamic
 * reconfigurability is off.
 */
static void netconsole_target_get(struct netconsole_target *nt)
{
}

static void netconsole_target_put(struct netconsole_target *nt)
{
}

static void populate_configfs_item(struct netconsole_target *nt,
                                   int cmdline_count)
{
}
#endif  /* CONFIG_NETCONSOLE_DYNAMIC */

/* Allocate and initialize with defaults.
 * Note that these targets get their config_item fields zeroed-out.
 */
static struct netconsole_target *alloc_and_init(void)
{
        struct netconsole_target *nt;

        nt = kzalloc(sizeof(*nt), GFP_KERNEL);
        if (!nt)
                return nt;

        if (IS_ENABLED(CONFIG_NETCONSOLE_EXTENDED_LOG))
                nt->extended = true;
        if (IS_ENABLED(CONFIG_NETCONSOLE_PREPEND_RELEASE))
                nt->release = true;

        nt->np.name = "netconsole";
        strscpy(nt->np.dev_name, "eth0", IFNAMSIZ);
        nt->np.local_port = 6665;
        nt->np.remote_port = 6666;
        eth_broadcast_addr(nt->np.remote_mac);

        return nt;
}

/* Clean up every target in the cleanup_list and move the clean targets back to
 * the main target_list.
 */
static void netconsole_process_cleanups_core(void)
{
        struct netconsole_target *nt, *tmp;
        unsigned long flags;

        /* The cleanup needs RTNL locked */
        ASSERT_RTNL();

        mutex_lock(&target_cleanup_list_lock);
        list_for_each_entry_safe(nt, tmp, &target_cleanup_list, list) {
                /* all entries in the cleanup_list needs to be disabled */
                WARN_ON_ONCE(nt->enabled);
                do_netpoll_cleanup(&nt->np);
                /* moved the cleaned target to target_list. Need to hold both
                 * locks
                 */
                spin_lock_irqsave(&target_list_lock, flags);
                list_move(&nt->list, &target_list);
                spin_unlock_irqrestore(&target_list_lock, flags);
        }
        WARN_ON_ONCE(!list_empty(&target_cleanup_list));
        mutex_unlock(&target_cleanup_list_lock);
}

#ifdef  CONFIG_NETCONSOLE_DYNAMIC

/*
 * Our subsystem hierarchy is:
 *
 * /sys/kernel/config/netconsole/
 *                              |
 *                              <target>/
 *                              |       enabled
 *                              |       release
 *                              |       dev_name
 *                              |       local_port
 *                              |       remote_port
 *                              |       local_ip
 *                              |       remote_ip
 *                              |       local_mac
 *                              |       remote_mac
 *                              |       userdata/
 *                              |               <key>/
 *                              |                       value
 *                              |               ...
 *                              |
 *                              <target>/...
 */

static struct netconsole_target *to_target(struct config_item *item)
{
        struct config_group *cfg_group;

        cfg_group = to_config_group(item);
        if (!cfg_group)
                return NULL;
        return container_of(to_config_group(item),
                            struct netconsole_target, group);
}

/* Do the list cleanup with the rtnl lock hold.  rtnl lock is necessary because
 * netdev might be cleaned-up by calling __netpoll_cleanup(),
 */
static void netconsole_process_cleanups(void)
{
        /* rtnl lock is called here, because it has precedence over
         * target_cleanup_list_lock mutex and target_cleanup_list
         */
        rtnl_lock();
        netconsole_process_cleanups_core();
        rtnl_unlock();
}

/* Get rid of possible trailing newline, returning the new length */
static void trim_newline(char *s, size_t maxlen)
{
        size_t len;

        len = strnlen(s, maxlen);
        if (s[len - 1] == '\n')
                s[len - 1] = '\0';
}

/*
 * Attribute operations for netconsole_target.
 */

static ssize_t enabled_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->enabled);
}

static ssize_t extended_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->extended);
}

static ssize_t release_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->release);
}

static ssize_t dev_name_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%s\n", to_target(item)->np.dev_name);
}

static ssize_t local_port_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->np.local_port);
}

static ssize_t remote_port_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->np.remote_port);
}

static ssize_t local_ip_show(struct config_item *item, char *buf)
{
        struct netconsole_target *nt = to_target(item);

        if (nt->np.ipv6)
                return sysfs_emit(buf, "%pI6c\n", &nt->np.local_ip.in6);
        else
                return sysfs_emit(buf, "%pI4\n", &nt->np.local_ip);
}

static ssize_t remote_ip_show(struct config_item *item, char *buf)
{
        struct netconsole_target *nt = to_target(item);

        if (nt->np.ipv6)
                return sysfs_emit(buf, "%pI6c\n", &nt->np.remote_ip.in6);
        else
                return sysfs_emit(buf, "%pI4\n", &nt->np.remote_ip);
}

static ssize_t local_mac_show(struct config_item *item, char *buf)
{
        struct net_device *dev = to_target(item)->np.dev;
        static const u8 bcast[ETH_ALEN] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };

        return sysfs_emit(buf, "%pM\n", dev ? dev->dev_addr : bcast);
}

static ssize_t remote_mac_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%pM\n", to_target(item)->np.remote_mac);
}

/*
 * This one is special -- targets created through the configfs interface
 * are not enabled (and the corresponding netpoll activated) by default.
 * The user is expected to set the desired parameters first (which
 * would enable him to dynamically add new netpoll targets for new
 * network interfaces as and when they come up).
 */
static ssize_t enabled_store(struct config_item *item,
                const char *buf, size_t count)
{
        struct netconsole_target *nt = to_target(item);
        unsigned long flags;
        bool enabled;
        ssize_t ret;

        mutex_lock(&dynamic_netconsole_mutex);
        ret = kstrtobool(buf, &enabled);
        if (ret)
                goto out_unlock;

        ret = -EINVAL;
        if (enabled == nt->enabled) {
                pr_info("network logging has already %s\n",
                        nt->enabled ? "started" : "stopped");
                goto out_unlock;
        }

        if (enabled) {  /* true */
                if (nt->release && !nt->extended) {
                        pr_err("Not enabling netconsole. Release feature requires extended log message");
                        goto out_unlock;
                }

                if (nt->extended && !console_is_registered(&netconsole_ext))
                        register_console(&netconsole_ext);

                /*
                 * Skip netpoll_parse_options() -- all the attributes are
                 * already configured via configfs. Just print them out.
                 */
                netpoll_print_options(&nt->np);

                ret = netpoll_setup(&nt->np);
                if (ret)
                        goto out_unlock;

                nt->enabled = true;
                pr_info("network logging started\n");
        } else {        /* false */
                /* We need to disable the netconsole before cleaning it up
                 * otherwise we might end up in write_msg() with
                 * nt->np.dev == NULL and nt->enabled == true
                 */
                mutex_lock(&target_cleanup_list_lock);
                spin_lock_irqsave(&target_list_lock, flags);
                nt->enabled = false;
                /* Remove the target from the list, while holding
                 * target_list_lock
                 */
                list_move(&nt->list, &target_cleanup_list);
                spin_unlock_irqrestore(&target_list_lock, flags);
                mutex_unlock(&target_cleanup_list_lock);
        }

        ret = strnlen(buf, count);
        /* Deferred cleanup */
        netconsole_process_cleanups();
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

static ssize_t release_store(struct config_item *item, const char *buf,
                             size_t count)
{
        struct netconsole_target *nt = to_target(item);
        bool release;
        ssize_t ret;

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                ret = -EINVAL;
                goto out_unlock;
        }

        ret = kstrtobool(buf, &release);
        if (ret)
                goto out_unlock;

        nt->release = release;

        ret = strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

static ssize_t extended_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);
        bool extended;
        ssize_t ret;

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                ret = -EINVAL;
                goto out_unlock;
        }

        ret = kstrtobool(buf, &extended);
        if (ret)
                goto out_unlock;

        nt->extended = extended;
        ret = strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

static ssize_t dev_name_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                mutex_unlock(&dynamic_netconsole_mutex);
                return -EINVAL;
        }

        strscpy(nt->np.dev_name, buf, IFNAMSIZ);
        trim_newline(nt->np.dev_name, IFNAMSIZ);

        mutex_unlock(&dynamic_netconsole_mutex);
        return strnlen(buf, count);
}

static ssize_t local_port_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);
        ssize_t ret = -EINVAL;

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        ret = kstrtou16(buf, 10, &nt->np.local_port);
        if (ret < 0)
                goto out_unlock;
        ret = strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

static ssize_t remote_port_store(struct config_item *item,
                const char *buf, size_t count)
{
        struct netconsole_target *nt = to_target(item);
        ssize_t ret = -EINVAL;

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        ret = kstrtou16(buf, 10, &nt->np.remote_port);
        if (ret < 0)
                goto out_unlock;
        ret = strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

static ssize_t local_ip_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);
        ssize_t ret = -EINVAL;

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        if (strnchr(buf, count, ':')) {
                const char *end;

                if (in6_pton(buf, count, nt->np.local_ip.in6.s6_addr, -1, &end) > 0) {
                        if (*end && *end != '\n') {
                                pr_err("invalid IPv6 address at: <%c>\n", *end);
                                goto out_unlock;
                        }
                        nt->np.ipv6 = true;
                } else
                        goto out_unlock;
        } else {
                if (!nt->np.ipv6)
                        nt->np.local_ip.ip = in_aton(buf);
                else
                        goto out_unlock;
        }

        ret = strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

static ssize_t remote_ip_store(struct config_item *item, const char *buf,
               size_t count)
{
        struct netconsole_target *nt = to_target(item);
        ssize_t ret = -EINVAL;

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        if (strnchr(buf, count, ':')) {
                const char *end;

                if (in6_pton(buf, count, nt->np.remote_ip.in6.s6_addr, -1, &end) > 0) {
                        if (*end && *end != '\n') {
                                pr_err("invalid IPv6 address at: <%c>\n", *end);
                                goto out_unlock;
                        }
                        nt->np.ipv6 = true;
                } else
                        goto out_unlock;
        } else {
                if (!nt->np.ipv6)
                        nt->np.remote_ip.ip = in_aton(buf);
                else
                        goto out_unlock;
        }

        ret = strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

static ssize_t remote_mac_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);
        u8 remote_mac[ETH_ALEN];
        ssize_t ret = -EINVAL;

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        if (!mac_pton(buf, remote_mac))
                goto out_unlock;
        if (buf[3 * ETH_ALEN - 1] && buf[3 * ETH_ALEN - 1] != '\n')
                goto out_unlock;
        memcpy(nt->np.remote_mac, remote_mac, ETH_ALEN);

        ret = strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

struct userdatum {
        struct config_item item;
        char value[MAX_USERDATA_VALUE_LENGTH];
};

static struct userdatum *to_userdatum(struct config_item *item)
{
        return container_of(item, struct userdatum, item);
}

struct userdata {
        struct config_group group;
};

static struct userdata *to_userdata(struct config_item *item)
{
        return container_of(to_config_group(item), struct userdata, group);
}

static struct netconsole_target *userdata_to_target(struct userdata *ud)
{
        struct config_group *netconsole_group;

        netconsole_group = to_config_group(ud->group.cg_item.ci_parent);
        return to_target(&netconsole_group->cg_item);
}

static ssize_t userdatum_value_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%s\n", &(to_userdatum(item)->value[0]));
}

static void update_userdata(struct netconsole_target *nt)
{
        int complete_idx = 0, child_count = 0;
        struct list_head *entry;

        /* Clear the current string in case the last userdatum was deleted */
        nt->userdata_length = 0;
        nt->userdata_complete[0] = 0;

        list_for_each(entry, &nt->userdata_group.cg_children) {
                struct userdatum *udm_item;
                struct config_item *item;

                if (child_count >= MAX_USERDATA_ITEMS)
                        break;
                child_count++;

                item = container_of(entry, struct config_item, ci_entry);
                udm_item = to_userdatum(item);

                /* Skip userdata with no value set */
                if (strnlen(udm_item->value, MAX_USERDATA_VALUE_LENGTH) == 0)
                        continue;

                /* This doesn't overflow userdata_complete since it will write
                 * one entry length (1/MAX_USERDATA_ITEMS long), entry count is
                 * checked to not exceed MAX items with child_count above
                 */
                complete_idx += scnprintf(&nt->userdata_complete[complete_idx],
                                          MAX_USERDATA_ENTRY_LENGTH, " %s=%s\n",
                                          item->ci_name, udm_item->value);
        }
        nt->userdata_length = strnlen(nt->userdata_complete,
                                      sizeof(nt->userdata_complete));
}

static ssize_t userdatum_value_store(struct config_item *item, const char *buf,
                                     size_t count)
{
        struct userdatum *udm = to_userdatum(item);
        struct netconsole_target *nt;
        struct userdata *ud;
        ssize_t ret;

        if (count > MAX_USERDATA_VALUE_LENGTH)
                return -EMSGSIZE;

        mutex_lock(&dynamic_netconsole_mutex);

        ret = strscpy(udm->value, buf, sizeof(udm->value));
        if (ret < 0)
                goto out_unlock;
        trim_newline(udm->value, sizeof(udm->value));

        ud = to_userdata(item->ci_parent);
        nt = userdata_to_target(ud);
        update_userdata(nt);
        ret = count;
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return ret;
}

CONFIGFS_ATTR(userdatum_, value);

static struct configfs_attribute *userdatum_attrs[] = {
        &userdatum_attr_value,
        NULL,
};

static void userdatum_release(struct config_item *item)
{
        kfree(to_userdatum(item));
}

static struct configfs_item_operations userdatum_ops = {
        .release = userdatum_release,
};

static const struct config_item_type userdatum_type = {
        .ct_item_ops    = &userdatum_ops,
        .ct_attrs       = userdatum_attrs,
        .ct_owner       = THIS_MODULE,
};

static struct config_item *userdatum_make_item(struct config_group *group,
                                               const char *name)
{
        struct netconsole_target *nt;
        struct userdatum *udm;
        struct userdata *ud;
        size_t child_count;

        if (strlen(name) > MAX_USERDATA_NAME_LENGTH)
                return ERR_PTR(-ENAMETOOLONG);

        ud = to_userdata(&group->cg_item);
        nt = userdata_to_target(ud);
        child_count = list_count_nodes(&nt->userdata_group.cg_children);
        if (child_count >= MAX_USERDATA_ITEMS)
                return ERR_PTR(-ENOSPC);

        udm = kzalloc(sizeof(*udm), GFP_KERNEL);
        if (!udm)
                return ERR_PTR(-ENOMEM);

        config_item_init_type_name(&udm->item, name, &userdatum_type);
        return &udm->item;
}

static void userdatum_drop(struct config_group *group, struct config_item *item)
{
        struct netconsole_target *nt;
        struct userdata *ud;

        ud = to_userdata(&group->cg_item);
        nt = userdata_to_target(ud);

        mutex_lock(&dynamic_netconsole_mutex);
        update_userdata(nt);
        config_item_put(item);
        mutex_unlock(&dynamic_netconsole_mutex);
}

static struct configfs_attribute *userdata_attrs[] = {
        NULL,
};

static struct configfs_group_operations userdata_ops = {
        .make_item              = userdatum_make_item,
        .drop_item              = userdatum_drop,
};

static const struct config_item_type userdata_type = {
        .ct_item_ops    = &userdatum_ops,
        .ct_group_ops   = &userdata_ops,
        .ct_attrs       = userdata_attrs,
        .ct_owner       = THIS_MODULE,
};

CONFIGFS_ATTR(, enabled);
CONFIGFS_ATTR(, extended);
CONFIGFS_ATTR(, dev_name);
CONFIGFS_ATTR(, local_port);
CONFIGFS_ATTR(, remote_port);
CONFIGFS_ATTR(, local_ip);
CONFIGFS_ATTR(, remote_ip);
CONFIGFS_ATTR_RO(, local_mac);
CONFIGFS_ATTR(, remote_mac);
CONFIGFS_ATTR(, release);

static struct configfs_attribute *netconsole_target_attrs[] = {
        &attr_enabled,
        &attr_extended,
        &attr_release,
        &attr_dev_name,
        &attr_local_port,
        &attr_remote_port,
        &attr_local_ip,
        &attr_remote_ip,
        &attr_local_mac,
        &attr_remote_mac,
        NULL,
};

/*
 * Item operations and type for netconsole_target.
 */

static void netconsole_target_release(struct config_item *item)
{
        kfree(to_target(item));
}

static struct configfs_item_operations netconsole_target_item_ops = {
        .release                = netconsole_target_release,
};

static const struct config_item_type netconsole_target_type = {
        .ct_attrs               = netconsole_target_attrs,
        .ct_item_ops            = &netconsole_target_item_ops,
        .ct_owner               = THIS_MODULE,
};

static void init_target_config_group(struct netconsole_target *nt,
                                     const char *name)
{
        config_group_init_type_name(&nt->group, name, &netconsole_target_type);
        config_group_init_type_name(&nt->userdata_group, "userdata",
                                    &userdata_type);
        configfs_add_default_group(&nt->userdata_group, &nt->group);
}

static struct netconsole_target *find_cmdline_target(const char *name)
{
        struct netconsole_target *nt, *ret = NULL;
        unsigned long flags;

        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry(nt, &target_list, list) {
                if (!strcmp(nt->group.cg_item.ci_name, name)) {
                        ret = nt;
                        break;
                }
        }
        spin_unlock_irqrestore(&target_list_lock, flags);

        return ret;
}

/*
 * Group operations and type for netconsole_subsys.
 */

static struct config_group *make_netconsole_target(struct config_group *group,
                                                   const char *name)
{
        struct netconsole_target *nt;
        unsigned long flags;

        /* Checking if a target by this name was created at boot time.  If so,
         * attach a configfs entry to that target.  This enables dynamic
         * control.
         */
        if (!strncmp(name, NETCONSOLE_PARAM_TARGET_PREFIX,
                     strlen(NETCONSOLE_PARAM_TARGET_PREFIX))) {
                nt = find_cmdline_target(name);
                if (nt) {
                        init_target_config_group(nt, name);
                        return &nt->group;
                }
        }

        nt = alloc_and_init();
        if (!nt)
                return ERR_PTR(-ENOMEM);

        /* Initialize the config_group member */
        init_target_config_group(nt, name);

        /* Adding, but it is disabled */
        spin_lock_irqsave(&target_list_lock, flags);
        list_add(&nt->list, &target_list);
        spin_unlock_irqrestore(&target_list_lock, flags);

        return &nt->group;
}

static void drop_netconsole_target(struct config_group *group,
                                   struct config_item *item)
{
        unsigned long flags;
        struct netconsole_target *nt = to_target(item);

        spin_lock_irqsave(&target_list_lock, flags);
        list_del(&nt->list);
        spin_unlock_irqrestore(&target_list_lock, flags);

        /*
         * The target may have never been enabled, or was manually disabled
         * before being removed so netpoll may have already been cleaned up.
         */
        if (nt->enabled)
                netpoll_cleanup(&nt->np);

        config_item_put(&nt->group.cg_item);
}

static struct configfs_group_operations netconsole_subsys_group_ops = {
        .make_group     = make_netconsole_target,
        .drop_item      = drop_netconsole_target,
};

static const struct config_item_type netconsole_subsys_type = {
        .ct_group_ops   = &netconsole_subsys_group_ops,
        .ct_owner       = THIS_MODULE,
};

/* The netconsole configfs subsystem */
static struct configfs_subsystem netconsole_subsys = {
        .su_group       = {
                .cg_item        = {
                        .ci_namebuf     = "netconsole",
                        .ci_type        = &netconsole_subsys_type,
                },
        },
};

static void populate_configfs_item(struct netconsole_target *nt,
                                   int cmdline_count)
{
        char target_name[16];

        snprintf(target_name, sizeof(target_name), "%s%d",
                 NETCONSOLE_PARAM_TARGET_PREFIX, cmdline_count);
        init_target_config_group(nt, target_name);
}

#endif  /* CONFIG_NETCONSOLE_DYNAMIC */

/* Handle network interface device notifications */
static int netconsole_netdev_event(struct notifier_block *this,
                                   unsigned long event, void *ptr)
{
        unsigned long flags;
        struct netconsole_target *nt, *tmp;
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        bool stopped = false;

        if (!(event == NETDEV_CHANGENAME || event == NETDEV_UNREGISTER ||
              event == NETDEV_RELEASE || event == NETDEV_JOIN))
                goto done;

        mutex_lock(&target_cleanup_list_lock);
        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry_safe(nt, tmp, &target_list, list) {
                netconsole_target_get(nt);
                if (nt->np.dev == dev) {
                        switch (event) {
                        case NETDEV_CHANGENAME:
                                strscpy(nt->np.dev_name, dev->name, IFNAMSIZ);
                                break;
                        case NETDEV_RELEASE:
                        case NETDEV_JOIN:
                        case NETDEV_UNREGISTER:
                                nt->enabled = false;
                                list_move(&nt->list, &target_cleanup_list);
                                stopped = true;
                        }
                }
                netconsole_target_put(nt);
        }
        spin_unlock_irqrestore(&target_list_lock, flags);
        mutex_unlock(&target_cleanup_list_lock);

        if (stopped) {
                const char *msg = "had an event";

                switch (event) {
                case NETDEV_UNREGISTER:
                        msg = "unregistered";
                        break;
                case NETDEV_RELEASE:
                        msg = "released slaves";
                        break;
                case NETDEV_JOIN:
                        msg = "is joining a master device";
                        break;
                }
                pr_info("network logging stopped on interface %s as it %s\n",
                        dev->name, msg);
        }

        /* Process target_cleanup_list entries. By the end, target_cleanup_list
         * should be empty
         */
        netconsole_process_cleanups_core();

done:
        return NOTIFY_DONE;
}

static struct notifier_block netconsole_netdev_notifier = {
        .notifier_call  = netconsole_netdev_event,
};

static void send_msg_no_fragmentation(struct netconsole_target *nt,
                                      const char *msg,
                                      int msg_len,
                                      int release_len)
{
        static char buf[MAX_PRINT_CHUNK]; /* protected by target_list_lock */
        const char *userdata = NULL;
        const char *release;

#ifdef CONFIG_NETCONSOLE_DYNAMIC
        userdata = nt->userdata_complete;
#endif

        if (release_len) {
                release = init_utsname()->release;

                scnprintf(buf, MAX_PRINT_CHUNK, "%s,%s", release, msg);
                msg_len += release_len;
        } else {
                memcpy(buf, msg, msg_len);
        }

        if (userdata)
                msg_len += scnprintf(&buf[msg_len],
                                     MAX_PRINT_CHUNK - msg_len,
                                     "%s", userdata);

        netpoll_send_udp(&nt->np, buf, msg_len);
}

static void append_release(char *buf)
{
        const char *release;

        release = init_utsname()->release;
        scnprintf(buf, MAX_PRINT_CHUNK, "%s,", release);
}

static void send_fragmented_body(struct netconsole_target *nt, char *buf,
                                 const char *msgbody, int header_len,
                                 int msgbody_len)
{
        const char *userdata = NULL;
        int body_len, offset = 0;
        int userdata_len = 0;

#ifdef CONFIG_NETCONSOLE_DYNAMIC
        userdata = nt->userdata_complete;
        userdata_len = nt->userdata_length;
#endif

        /* body_len represents the number of bytes that will be sent. This is
         * bigger than MAX_PRINT_CHUNK, thus, it will be split in multiple
         * packets
         */
        body_len = msgbody_len + userdata_len;

        /* In each iteration of the while loop below, we send a packet
         * containing the header and a portion of the body. The body is
         * composed of two parts: msgbody and userdata. We keep track of how
         * many bytes have been sent so far using the offset variable, which
         * ranges from 0 to the total length of the body.
         */
        while (offset < body_len) {
                int this_header = header_len;
                bool msgbody_written = false;
                int this_offset = 0;
                int this_chunk = 0;

                this_header += scnprintf(buf + this_header,
                                         MAX_PRINT_CHUNK - this_header,
                                         ",ncfrag=%d/%d;", offset,
                                         body_len);

                /* Not all msgbody data has been written yet */
                if (offset < msgbody_len) {
                        this_chunk = min(msgbody_len - offset,
                                         MAX_PRINT_CHUNK - this_header);
                        if (WARN_ON_ONCE(this_chunk <= 0))
                                return;
                        memcpy(buf + this_header, msgbody + offset, this_chunk);
                        this_offset += this_chunk;
                }

                /* msgbody was finally written, either in the previous
                 * messages and/or in the current buf. Time to write
                 * the userdata.
                 */
                msgbody_written |= offset + this_offset >= msgbody_len;

                /* Msg body is fully written and there is pending userdata to
                 * write, append userdata in this chunk
                 */
                if (msgbody_written && offset + this_offset < body_len) {
                        /* Track how much user data was already sent. First
                         * time here, sent_userdata is zero
                         */
                        int sent_userdata = (offset + this_offset) - msgbody_len;
                        /* offset of bytes used in current buf */
                        int preceding_bytes = this_chunk + this_header;

                        if (WARN_ON_ONCE(sent_userdata < 0))
                                return;

                        this_chunk = min(userdata_len - sent_userdata,
                                         MAX_PRINT_CHUNK - preceding_bytes);
                        if (WARN_ON_ONCE(this_chunk < 0))
                                /* this_chunk could be zero if all the previous
                                 * message used all the buffer. This is not a
                                 * problem, userdata will be sent in the next
                                 * iteration
                                 */
                                return;

                        memcpy(buf + this_header + this_offset,
                               userdata + sent_userdata,
                               this_chunk);
                        this_offset += this_chunk;
                }

                netpoll_send_udp(&nt->np, buf, this_header + this_offset);
                offset += this_offset;
        }
}

static void send_msg_fragmented(struct netconsole_target *nt,
                                const char *msg,
                                int msg_len,
                                int release_len)
{
        static char buf[MAX_PRINT_CHUNK]; /* protected by target_list_lock */
        int header_len, msgbody_len;
        const char *msgbody;

        /* need to insert extra header fields, detect header and msgbody */
        msgbody = memchr(msg, ';', msg_len);
        if (WARN_ON_ONCE(!msgbody))
                return;

        header_len = msgbody - msg;
        msgbody_len = msg_len - header_len - 1;
        msgbody++;

        /*
         * Transfer multiple chunks with the following extra header.
         * "ncfrag=<byte-offset>/<total-bytes>"
         */
        if (release_len)
                append_release(buf);

        /* Copy the header into the buffer */
        memcpy(buf + release_len, msg, header_len);
        header_len += release_len;

        /* for now on, the header will be persisted, and the msgbody
         * will be replaced
         */
        send_fragmented_body(nt, buf, msgbody, header_len, msgbody_len);
}

/**
 * send_ext_msg_udp - send extended log message to target
 * @nt: target to send message to
 * @msg: extended log message to send
 * @msg_len: length of message
 *
 * Transfer extended log @msg to @nt.  If @msg is longer than
 * MAX_PRINT_CHUNK, it'll be split and transmitted in multiple chunks with
 * ncfrag header field added to identify them.
 */
static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
                             int msg_len)
{
        int userdata_len = 0;
        int release_len = 0;

#ifdef CONFIG_NETCONSOLE_DYNAMIC
        userdata_len = nt->userdata_length;
#endif

        if (nt->release)
                release_len = strlen(init_utsname()->release) + 1;

        if (msg_len + release_len + userdata_len <= MAX_PRINT_CHUNK)
                return send_msg_no_fragmentation(nt, msg, msg_len, release_len);

        return send_msg_fragmented(nt, msg, msg_len, release_len);
}

static void write_ext_msg(struct console *con, const char *msg,
                          unsigned int len)
{
        struct netconsole_target *nt;
        unsigned long flags;

        if ((oops_only && !oops_in_progress) || list_empty(&target_list))
                return;

        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry(nt, &target_list, list)
                if (nt->extended && nt->enabled && netif_running(nt->np.dev))
                        send_ext_msg_udp(nt, msg, len);
        spin_unlock_irqrestore(&target_list_lock, flags);
}

static void write_msg(struct console *con, const char *msg, unsigned int len)
{
        int frag, left;
        unsigned long flags;
        struct netconsole_target *nt;
        const char *tmp;

        if (oops_only && !oops_in_progress)
                return;
        /* Avoid taking lock and disabling interrupts unnecessarily */
        if (list_empty(&target_list))
                return;

        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry(nt, &target_list, list) {
                if (!nt->extended && nt->enabled && netif_running(nt->np.dev)) {
                        /*
                         * We nest this inside the for-each-target loop above
                         * so that we're able to get as much logging out to
                         * at least one target if we die inside here, instead
                         * of unnecessarily keeping all targets in lock-step.
                         */
                        tmp = msg;
                        for (left = len; left;) {
                                frag = min(left, MAX_PRINT_CHUNK);
                                netpoll_send_udp(&nt->np, tmp, frag);
                                tmp += frag;
                                left -= frag;
                        }
                }
        }
        spin_unlock_irqrestore(&target_list_lock, flags);
}

/* Allocate new target (from boot/module param) and setup netpoll for it */
static struct netconsole_target *alloc_param_target(char *target_config,
                                                    int cmdline_count)
{
        struct netconsole_target *nt;
        int err;

        nt = alloc_and_init();
        if (!nt) {
                err = -ENOMEM;
                goto fail;
        }

        if (*target_config == '+') {
                nt->extended = true;
                target_config++;
        }

        if (*target_config == 'r') {
                if (!nt->extended) {
                        pr_err("Netconsole configuration error. Release feature requires extended log message");
                        err = -EINVAL;
                        goto fail;
                }
                nt->release = true;
                target_config++;
        }

        /* Parse parameters and setup netpoll */
        err = netpoll_parse_options(&nt->np, target_config);
        if (err)
                goto fail;

        err = netpoll_setup(&nt->np);
        if (err) {
                pr_err("Not enabling netconsole for %s%d. Netpoll setup failed\n",
                       NETCONSOLE_PARAM_TARGET_PREFIX, cmdline_count);
                if (!IS_ENABLED(CONFIG_NETCONSOLE_DYNAMIC))
                        /* only fail if dynamic reconfiguration is set,
                         * otherwise, keep the target in the list, but disabled.
                         */
                        goto fail;
        } else {
                nt->enabled = true;
        }
        populate_configfs_item(nt, cmdline_count);

        return nt;

fail:
        kfree(nt);
        return ERR_PTR(err);
}

/* Cleanup netpoll for given target (from boot/module param) and free it */
static void free_param_target(struct netconsole_target *nt)
{
        netpoll_cleanup(&nt->np);
        kfree(nt);
}

static struct console netconsole_ext = {
        .name   = "netcon_ext",
        .flags  = CON_ENABLED | CON_EXTENDED,
        .write  = write_ext_msg,
};

static struct console netconsole = {
        .name   = "netcon",
        .flags  = CON_ENABLED,
        .write  = write_msg,
};

static int __init init_netconsole(void)
{
        int err;
        struct netconsole_target *nt, *tmp;
        unsigned int count = 0;
        bool extended = false;
        unsigned long flags;
        char *target_config;
        char *input = config;

        if (strnlen(input, MAX_PARAM_LENGTH)) {
                while ((target_config = strsep(&input, ";"))) {
                        nt = alloc_param_target(target_config, count);
                        if (IS_ERR(nt)) {
                                if (IS_ENABLED(CONFIG_NETCONSOLE_DYNAMIC))
                                        continue;
                                err = PTR_ERR(nt);
                                goto fail;
                        }
                        /* Dump existing printks when we register */
                        if (nt->extended) {
                                extended = true;
                                netconsole_ext.flags |= CON_PRINTBUFFER;
                        } else {
                                netconsole.flags |= CON_PRINTBUFFER;
                        }

                        spin_lock_irqsave(&target_list_lock, flags);
                        list_add(&nt->list, &target_list);
                        spin_unlock_irqrestore(&target_list_lock, flags);
                        count++;
                }
        }

        err = register_netdevice_notifier(&netconsole_netdev_notifier);
        if (err)
                goto fail;

        err = dynamic_netconsole_init();
        if (err)
                goto undonotifier;

        if (extended)
                register_console(&netconsole_ext);
        register_console(&netconsole);
        pr_info("network logging started\n");

        return err;

undonotifier:
        unregister_netdevice_notifier(&netconsole_netdev_notifier);

fail:
        pr_err("cleaning up\n");

        /*
         * Remove all targets and destroy them (only targets created
         * from the boot/module option exist here). Skipping the list
         * lock is safe here, and netpoll_cleanup() will sleep.
         */
        list_for_each_entry_safe(nt, tmp, &target_list, list) {
                list_del(&nt->list);
                free_param_target(nt);
        }

        return err;
}

static void __exit cleanup_netconsole(void)
{
        struct netconsole_target *nt, *tmp;

        if (console_is_registered(&netconsole_ext))
                unregister_console(&netconsole_ext);
        unregister_console(&netconsole);
        dynamic_netconsole_exit();
        unregister_netdevice_notifier(&netconsole_netdev_notifier);

        /*
         * Targets created via configfs pin references on our module
         * and would first be rmdir(2)'ed from userspace. We reach
         * here only when they are already destroyed, and only those
         * created from the boot/module option are left, so remove and
         * destroy them. Skipping the list lock is safe here, and
         * netpoll_cleanup() will sleep.
         */
        list_for_each_entry_safe(nt, tmp, &target_list, list) {
                list_del(&nt->list);
                free_param_target(nt);
        }
}

/*
 * Use late_initcall to ensure netconsole is
 * initialized after network device driver if built-in.
 *
 * late_initcall() and module_init() are identical if built as module.
 */
late_initcall(init_netconsole);
module_exit(cleanup_netconsole);