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net: netconsole: cache userdata formatted string in netconsole_target

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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: Breno Leitao <leitao@debian.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Matthew Wood <thepacketgeek@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Matthew Wood 2024-02-04 15:27:37 -08:00 committed by David S. Miller
parent 8a6d5fec6c
commit df03f830d0
1 changed files with 61 additions and 0 deletions
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61
drivers/net/netconsole.c
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@ -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 = {