Commit df03f830 authored by Matthew Wood's avatar Matthew Wood Committed by David S. Miller
Browse files

net: netconsole: cache userdata formatted string in netconsole_target 



Store a formatted string for userdata that will be appended to netconsole
messages. The string has a capacity of 4KB, as calculated by the userdatum
entry length of 256 bytes and a max of 16 userdata entries.

Update the stored netconsole_target->userdata_complete string with the new
formatted userdata values when a userdatum is created, edited, or
removed. Each userdata entry contains a trailing newline, which will be
formatted as such in netconsole messages::

    6.7.0-rc8-virtme,12,500,1646292204,-;test
    release=foo
    something=bar
    6.7.0-rc8-virtme,12,500,1646292204,-;another test
    release=foo
    something=bar

Enforcement of MAX_USERDATA_ITEMS is done in userdatum_make_item;
update_userdata will not check for this case but will skip any userdata
children over the limit of MAX_USERDATA_ITEMs.

If a userdata entry/dir is created but no value is provided, that entry
will be skipped. This is in part because update_userdata() can't be
called in userdatum_make_item() since the item will not have been added
to the userdata config_group children yet. To preserve the experience of
adding an empty userdata that doesn't show up in the netconsole
messages, purposefully skip empty userdata items even when
update_userdata() can be called.

Co-developed-by: default avatarBreno Leitao <leitao@debian.org>
Signed-off-by: default avatarBreno Leitao <leitao@debian.org>
Signed-off-by: default avatarMatthew Wood <thepacketgeek@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8a6d5fec

drivers/net/netconsole.c

+61 −0
Original line number Diff line number Diff line
@@ -85,6 +85,8 @@ static struct console netconsole_ext; 
 * @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
@@ -109,6 +111,8 @@ struct netconsole_target { 
#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;
@@ -638,10 +642,48 @@ 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;

	int ret;



	if (count > MAX_USERDATA_VALUE_LENGTH)
@@ -654,6 +696,10 @@ static ssize_t userdatum_value_store(struct config_item *item, const char *buf, 
		goto out_unlock;

	trim_newline(udm->value, sizeof(udm->value));



	ud = to_userdata(item->ci_parent);

	nt = userdata_to_target(ud);

	update_userdata(nt);



	mutex_unlock(&dynamic_netconsole_mutex);

	return count;

out_unlock:
@@ -708,12 +754,27 @@ static struct config_item *userdatum_make_item(struct config_group *group, 
	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 struct config_item_type userdata_type = {