Messages in this thread | | | Date | Mon, 13 Dec 2021 22:46:41 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH v4 3/4] tracing: Add helper functions to simplify event_command.parse() callback handling |
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Hi Tom,
On Fri, 10 Dec 2021 15:16:24 -0600 Tom Zanussi <zanussi@kernel.org> wrote:
> +/* > + * Event trigger parsing helper functions. > + * > + * These functions help make it easier to write an event trigger > + * parsing function i.e. the struct event_command.parse() callback > + * function responsible for parsing and registering a trigger command > + * written to the 'trigger' file. > + * > + * A trigger command (or just 'trigger' for short) takes the form: > + * [trigger] [if filter] > + * > + * The struct event_command.parse() callback (and other struct > + * event_command functions) refer to several components of a trigger > + * command. Those same components are referenced by the event trigger > + * parsing helper functions defined below. These components are: > + * > + * cmd - the trigger command name > + * glob - the trigger command name optionally prefaced with '!' > + * param - text remaining after the command is stripped of cmd and ':' > + * filter - the optional filter text following (and including) 'if' > + * > + * To illustrate the use of these componenents, here are some concrete > + * examples. For the following triggers: > + * > + * echo 'traceon:5 if pid == 0' > trigger > + * - 'traceon' is both cmd and glob > + * - '5 if pid == 0' is the param > + * - 'if pid == 0' is the filter
I would like to know why both 'param' and 'filter' has "if pid == 0". I thought that part is (generic) filter and not a parameter.
If I missed any discussion on this point, sorry about that.
> + * > + * echo 'enable_event:sys:event:n' > trigger > + * - 'enable_event' is both cmd and glob > + * - 'sys:event:n' is the param > + * - there is no filter > + * > + * echo 'hist:keys=pid if prio > 50' > trigger > + * - 'hist' is both cmd and glob > + * - 'keys=pid if prio > 50' is the param > + * - 'if prio > 50' is the filter > + * > + * echo '!enable_event:sys:event:n' > trigger > + * - 'enable_event' the cmd > + * - '!enable_event' is the glob > + * - 'sys:event:n' is the param > + * - there is no filter > + * > + * echo 'traceoff' > trigger > + * - 'traceoff' is both cmd and glob > + * - there is no param > + * - there is no filter > + * > + * There are a few different categories of event trigger covered by > + * these helpers: > + * > + * - triggers that don't require a parameter e.g. traceon > + * - triggers that do require a parameter e.g. enable_event and hist > + * - triggers that though they may not require a param may support an > + * optional 'n' param (n = number of times the trigger should fire) > + * e.g.: traceon:5 or enable_event:sys:event:n > + * - triggers that do not support an 'n' param e.g. hist > + * > + * These functions can be used or ignored as necessary - it all > + * depends on the complexity of the trigger, and the granularity of > + * the functions supported reflects the fact that some implementations > + * may need to customize certain aspects of their implementations and > + * won't need certain functions. For instance, the hist trigger > + * implementation doesn't use event_trigger_separate_filter() because > + * it has special requirements for handling the filter. > + */ > + > +/** > + * event_trigger_check_remove - check whether an event trigger specifies remove > + * @glob: The trigger command string, with optional remove(!) operator > + * > + * The event trigger callback implementations pass in 'glob' as a > + * parameter. This is the command name either with or without a > + * remove(!) operator. This function simply parses the glob and > + * determines whether the command corresponds to a trigger removal or > + * a trigger addition. > + * > + * Return: true if this is a remove command, false otherwise > + */ > +bool event_trigger_check_remove(const char *glob) > +{ > + return (glob && glob[0] == '!') ? true : false; > +} > + > +/** > + * event_trigger_empty_param - check whether the param is empty > + * @param: The trigger param string > + * > + * The event trigger callback implementations pass in 'param' as a > + * parameter. This corresponds to the string following the command > + * name minus the command name. This function can be called by a > + * callback implementation for any command that requires a param; a > + * callback that doesn't require a param can ignore it. > + * > + * Return: true if this is an empty param, false otherwise > + */ > +bool event_trigger_empty_param(const char *param) > +{ > + return !param; > +} > + > +/** > + * event_trigger_separate_filter - separate an event trigger from a filter > + * @param: The param string containing trigger and possibly filter > + * @trigger: outparam, will be filled with a pointer to the trigger > + * @filter: outparam, will be filled with a pointer to the filter > + * @param_required: Specifies whether or not the param string is required > + * > + * Given a param string of the form '[trigger] [if filter]', this > + * function separates the filter from the trigger and returns the > + * trigger in *trigger and the filter in *filter. Either the *trigger > + * or the *filter may be set to NULL by this function - if not set to > + * NULL, they will contain strings corresponding to the trigger and > + * filter. > + * > + * There are two cases that need to be handled with respect to the > + * passed-in param: either the param is required, or it is not > + * required. If @param_required is set, and there's no param, it will > + * return -EINVAL. If @param_required is not set and there's a param > + * that starts with a number, that corresponds to the case of a > + * trigger with :n (n = number of times the trigger should fire) and > + * the parsing continues normally; otherwise the function just returns > + * and assumes param just contains a filter and there's nothing else > + * to do. > + * > + * Return: 0 on success, errno otherwise > + */ > +int event_trigger_separate_filter(char *param_and_filter, char **param, > + char **filter, bool param_required) > +{ > + int ret = 0; > + > + *param = *filter = NULL; > + > + if (!param_and_filter) { > + if (param_required) > + ret = -EINVAL; > + goto out; > + } > + > + /* > + * Here we check for an optional param. The only legal > + * optional param is :n, and if that's the case, continue > + * below. Otherwise we assume what's left is a filter and > + * return it as the filter string for the caller to deal with. > + */ > + if (!param_required && param_and_filter && !isdigit(param_and_filter[0])) { > + *filter = param_and_filter; > + goto out; > + } > + > + /* > + * Separate the param from the filter (param [if filter]). > + * Here we have either an optional :n param or a required > + * param and an optional filter. > + */ > + *param = strsep(¶m_and_filter, " \t"); > + if (!*param) { > + ret = -EINVAL;
This seems not happen because this means "!param_and_filter" and that is already checked at the entry of this function.
> + goto out; > + } > + > + /* > + * Here we have a filter, though it may be empty. > + */ > + if (param_and_filter) { > + *filter = skip_spaces(param_and_filter); > + if (!**filter) > + *filter = NULL; > + } > +out: > + return ret; > +} > + > +/** > + * event_trigger_alloc - allocate and init event_trigger_data for a trigger > + * @cmd_ops: The event_command operations for the trigger > + * @cmd: The cmd string > + * @param: The param string > + * @private_data: User data to associate with the event trigger > + * > + * Allocate an event_trigger_data instance and initialize it. The > + * @cmd_ops are used along with the @cmd and @param to get the > + * trigger_ops to assign to the event_trigger_data. @private_data can > + * also be passed in and associated with the event_trigger_data. > + * > + * Use event_trigger_free() to free an event_trigger_data object. > + * > + * Return: The trigger_data object success, NULL otherwise > + */ > +struct event_trigger_data *event_trigger_alloc(struct event_command *cmd_ops, > + char *cmd, > + char *param, > + void *private_data) > +{ > + struct event_trigger_data *trigger_data; > + struct event_trigger_ops *trigger_ops; > + > + trigger_ops = cmd_ops->get_trigger_ops(cmd, param); > + > + trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL); > + if (!trigger_data) > + return NULL; > + > + trigger_data->count = -1; > + trigger_data->ops = trigger_ops; > + trigger_data->cmd_ops = cmd_ops; > + trigger_data->private_data = private_data; > + > + INIT_LIST_HEAD(&trigger_data->list); > + INIT_LIST_HEAD(&trigger_data->named_list); > + RCU_INIT_POINTER(trigger_data->filter, NULL); > + > + return trigger_data; > +} > + > +/** > + * event_trigger_parse_num - parse and return the number param for a trigger > + * @trigger: The trigger string
Does this mean trigger parameter?
> + * @trigger_data: The trigger_data for the trigger > + * > + * Parse the :n (n = number of times the trigger should fire) param > + * and set the count variable in the trigger_data to the parsed count. > + * > + * Return: 0 on success, errno otherwise > + */ > +int event_trigger_parse_num(char *trigger, > + struct event_trigger_data *trigger_data) > +{ > + char *number; > + int ret = 0; > + > + if (trigger) { > + number = strsep(&trigger, ":"); > + > + if (!strlen(number)) > + return -EINVAL; > + > + /* > + * We use the callback data field (which is a pointer) > + * as our counter. > + */ > + ret = kstrtoul(number, 0, &trigger_data->count); > + } > + > + return ret; > +}
Does this work with '!enable_event:sys:event:n' case? (we need to find the last parameter.)
Thank you,
-- Masami Hiramatsu <mhiramat@kernel.org>
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