From df03f830d099f0811281a222aefdd9d400fa0b72 Mon Sep 17 00:00:00 2001 From: Matthew Wood Date: Sun, 4 Feb 2024 15:27:37 -0800 Subject: [PATCH] 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: Breno Leitao Signed-off-by: Breno Leitao Signed-off-by: Matthew Wood Signed-off-by: David S. Miller --- drivers/net/netconsole.c | 61 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index 3618b9ebcce4..e4d6ba0b50ef 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -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 = {