Date:   Mon, 27 Jan 2020 22:44:48 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Tom Zanussi <zanussi@...nel.org>
Cc:     rostedt@...dmis.org, artem.bityutskiy@...ux.intel.com,
        mhiramat@...nel.org, linux-kernel@...r.kernel.org,
        linux-rt-users@...r.kernel.org, ndesaulniers@...gle.com
Subject: Re: [PATCH v3 04/12] tracing: Add dynamic event command creation
 interface

Hi Tom,

On Fri, 24 Jan 2020 16:56:15 -0600
Tom Zanussi <zanussi@...nel.org> wrote:

> Add an interface used to build up dynamic event creation commands,
> such as synthetic and kprobe events.  Interfaces specific to those
> particular types of events and others can be built on top of this
> interface.
> 
> Command creation is started by first using the dynevent_cmd_init()
> function to initialize the dynevent_cmd object.  Following that, args
> are appended and optionally checked by the dynevent_arg_add() and
> dynevent_arg_pair_add() functions, which use objects representing
> arguments and pairs of arguments, initialized respectively by
> dynevent_arg_init() and dynevent_arg_pair_init().  Finally, once all
> args have been successfully added, the command is finalized and
> actually created using dynevent_create().
> 
> The code here for actually printing into the dyn_event->cmd buffer
> using snprintf() etc was adapted from v4 of Masami's 'tracing/boot:
> Add synthetic event support' patch.

OK, these code are only for dyn_event. Then, it should be implemented
in kernel/trace/trace_dynevent.{c,h}. Of course some exported functions
should be in include/linux/trace_events.h.
Or, would you have any reason to put them in trace_events.c ?

Thank you,

> 
> Signed-off-by: Tom Zanussi <zanussi@...nel.org>
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  include/linux/trace_events.h |  23 +++++
>  kernel/trace/trace.h         |  34 ++++++
>  kernel/trace/trace_events.c  | 240 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 297 insertions(+)
> 
> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
> index 25fe743bcbaf..651b03d5e272 100644
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -354,6 +354,29 @@ extern struct trace_event_file *trace_get_event_file(const char *instance,
>  						     const char *event);
>  extern void trace_put_event_file(struct trace_event_file *file);
>  
> +#define MAX_DYNEVENT_CMD_LEN	(2048)
> +
> +enum dynevent_type {
> +	DYNEVENT_TYPE_NONE,
> +};
> +
> +struct dynevent_cmd;
> +
> +typedef int (*dynevent_create_fn_t)(struct dynevent_cmd *cmd);
> +
> +struct dynevent_cmd {
> +	char			*buf;
> +	const char		*event_name;
> +	int			maxlen;
> +	int			remaining;
> +	unsigned int		n_fields;
> +	enum dynevent_type	type;
> +	dynevent_create_fn_t	run_command;
> +	void			*private_data;
> +};
> +
> +extern int dynevent_create(struct dynevent_cmd *cmd);
> +
>  extern int synth_event_delete(const char *name);
>  
>  /*
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 8fe3b16c8cec..0e8afc32d972 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -1877,6 +1877,40 @@ static inline bool event_command_needs_rec(struct event_command *cmd_ops)
>  
>  extern int trace_event_enable_disable(struct trace_event_file *file,
>  				      int enable, int soft_disable);
> +
> +extern void dynevent_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen,
> +			      enum dynevent_type type,
> +			      dynevent_create_fn_t run_command);
> +
> +typedef int (*dynevent_check_arg_fn_t)(void *data);
> +
> +struct dynevent_arg {
> +	const char		*str;
> +	char			separator; /* e.g. ';', ',', or nothing */
> +	dynevent_check_arg_fn_t	check_arg;
> +};
> +
> +extern void dynevent_arg_init(struct dynevent_arg *arg,
> +			      dynevent_check_arg_fn_t check_arg,
> +			      char separator);
> +extern int dynevent_arg_add(struct dynevent_cmd *cmd,
> +			    struct dynevent_arg *arg);
> +
> +struct dynevent_arg_pair {
> +	const char		*lhs;
> +	const char		*rhs;
> +	char			operator; /* e.g. '=' or nothing */
> +	char			separator; /* e.g. ';', ',', or nothing */
> +	dynevent_check_arg_fn_t	check_arg;
> +};
> +
> +extern void dynevent_arg_pair_init(struct dynevent_arg_pair *arg_pair,
> +				   dynevent_check_arg_fn_t check_arg,
> +				   char operator, char separator);
> +extern int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
> +				 struct dynevent_arg_pair *arg_pair);
> +extern int dynevent_str_add(struct dynevent_cmd *cmd, const char *str);
> +
>  extern int tracing_alloc_snapshot(void);
>  extern void tracing_snapshot_cond(struct trace_array *tr, void *cond_data);
>  extern int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data, cond_update_fn_t update);
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 402426a82cfb..aa56bb6ff6ca 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -3300,6 +3300,246 @@ void __init trace_event_init(void)
>  	event_trace_enable();
>  }
>  
> +/**
> + * dynevent_arg_add - Add an arg to a dynevent_cmd
> + * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
> + * @arg: The argument to append to the current cmd
> + *
> + * Append an argument to a dynevent_cmd.  The argument string will be
> + * appended to the current cmd string, followed by a separator, if
> + * applicable.  Before the argument is added, the check_arg()
> + * function, if defined, is called.
> + *
> + * The cmd string, separator, and check_arg() function should be set
> + * using the dynevent_arg_init() before any arguments are added using
> + * this function.
> + *
> + * Return: 0 if successful, error otherwise.
> + */
> +int dynevent_arg_add(struct dynevent_cmd *cmd,
> +		     struct dynevent_arg *arg)
> +{
> +	int ret = 0;
> +	int delta;
> +	char *q;
> +
> +	if (arg->check_arg) {
> +		ret = arg->check_arg(arg);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	q = cmd->buf + (cmd->maxlen - cmd->remaining);
> +
> +	delta = snprintf(q, cmd->remaining, " %s%c", arg->str, arg->separator);
> +	if (delta >= cmd->remaining) {
> +		pr_err("String is too long: %s\n", arg->str);
> +		return -E2BIG;
> +	}
> +	cmd->remaining -= delta;
> +
> +	return ret;
> +}
> +
> +/**
> + * dynevent_arg_pair_add - Add an arg pair to a dynevent_cmd
> + * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
> + * @arg_pair: The argument pair to append to the current cmd
> + *
> + * Append an argument pair to a dynevent_cmd.  An argument pair
> + * consists of a left-hand-side argument and a right-hand-side
> + * argument separated by an operator, which can be whitespace, all
> + * followed by a separator, if applicable.  This can be used to add
> + * arguments of the form 'type variable_name;' or 'x+y'.
> + *
> + * The lhs argument string will be appended to the current cmd string,
> + * followed by an operator, if applicable, followd by the rhs string,
> + * followed finally by a separator, if applicable.  Before anything is
> + * added, the check_arg() function, if defined, is called.
> + *
> + * The cmd strings, operator, separator, and check_arg() function
> + * should be set using the dynevent_arg_pair_init() before any arguments
> + * are added using this function.
> + *
> + * Return: 0 if successful, error otherwise.
> + */
> +int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
> +			  struct dynevent_arg_pair *arg_pair)
> +{
> +	int ret = 0;
> +	int delta;
> +	char *q;
> +
> +	if (arg_pair->check_arg) {
> +		ret = arg_pair->check_arg(arg_pair);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	q = cmd->buf + (cmd->maxlen - cmd->remaining);
> +
> +	delta = snprintf(q, cmd->remaining, " %s%c", arg_pair->lhs,
> +			 arg_pair->operator);
> +	if (delta >= cmd->remaining) {
> +		pr_err("field string is too long: %s\n", arg_pair->lhs);
> +		return -E2BIG;
> +	}
> +	cmd->remaining -= delta; q += delta;
> +
> +	delta = snprintf(q, cmd->remaining, "%s%c", arg_pair->rhs,
> +			 arg_pair->separator);
> +	if (delta >= cmd->remaining) {
> +		pr_err("field string is too long: %s\n", arg_pair->rhs);
> +		return -E2BIG;
> +	}
> +	cmd->remaining -= delta; q += delta;
> +
> +	return ret;
> +}
> +
> +/**
> + * dynevent_str_add - Add a string to a dynevent_cmd
> + * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
> + * @str: The string to append to the current cmd
> + *
> + * Append a string to a dynevent_cmd.  The string will be appended to
> + * the current cmd string as-is, with nothing prepended or appended.
> + *
> + * Return: 0 if successful, error otherwise.
> + */
> +int dynevent_str_add(struct dynevent_cmd *cmd, const char *str)
> +{
> +	int ret = 0;
> +	int delta;
> +	char *q;
> +
> +	q = cmd->buf + (cmd->maxlen - cmd->remaining);
> +
> +	delta = snprintf(q, cmd->remaining, "%s", str);
> +	if (delta >= cmd->remaining) {
> +		pr_err("String is too long: %s\n", str);
> +		return -E2BIG;
> +	}
> +	cmd->remaining -= delta;
> +
> +	return ret;
> +}
> +
> +/**
> + * dynevent_cmd_init - Initialize a dynevent_cmd object
> + * @cmd: A pointer to the dynevent_cmd struct representing the cmd
> + * @buf: A pointer to the buffer to generate the command into
> + * @maxlen: The length of the buffer the command will be generated into
> + * @type: The type of the cmd, checked against further operations
> + * @run_command: The type-specific function that will actually run the command
> + *
> + * Initialize a dynevent_cmd.  A dynevent_cmd is used to build up and
> + * run dynamic event creation commands, such as commands for creating
> + * synthetic and kprobe events.  Before calling any of the functions
> + * used to build the command, a dynevent_cmd object should be
> + * instantiated and initialized using this function.
> + *
> + * The initialization sets things up by saving a pointer to the
> + * user-supplied buffer and its length via the @buf and @maxlen
> + * params, and by saving the cmd-specific @type and @run_command
> + * params which are used to check subsequent dynevent_cmd operations
> + * and actually run the command when complete.
> + */
> +void dynevent_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen,
> +		       enum dynevent_type type,
> +		       dynevent_create_fn_t run_command)
> +{
> +	memset(cmd, '\0', sizeof(*cmd));
> +
> +	cmd->buf = buf;
> +	cmd->maxlen = maxlen;
> +	cmd->remaining = cmd->maxlen;
> +	cmd->type = type;
> +	cmd->run_command = run_command;
> +}
> +
> +/**
> + * dynevent_arg_init - Initialize a dynevent_arg object
> + * @arg: A pointer to the dynevent_arg struct representing the arg
> + * @check_arg: An (optional) pointer to a function checking arg sanity
> + * @separator: An (optional) separator, appended after adding the arg
> + *
> + * Initialize a dynevent_arg object.  A dynevent_arg represents an
> + * object used to append single arguments to the current command
> + * string.  The @check_arg function, if present, will be used to check
> + * the sanity of the current arg string (which is directly set by the
> + * caller).  After the arg string is successfully appended to the
> + * command string, the optional @separator is appended.  If no
> + * separator was specified when initializing the arg, a space will be
> + * appended.
> + */
> +void dynevent_arg_init(struct dynevent_arg *arg,
> +		       dynevent_check_arg_fn_t check_arg,
> +		       char separator)
> +{
> +	memset(arg, '\0', sizeof(*arg));
> +
> +	if (!separator)
> +		separator = ' ';
> +	arg->separator = separator;
> +
> +	arg->check_arg = check_arg;
> +}
> +
> +/**
> + * dynevent_arg_pair_init - Initialize a dynevent_arg_pair object
> + * @arg_pair: A pointer to the dynevent_arg_pair struct representing the arg
> + * @check_arg: An (optional) pointer to a function checking arg sanity
> + * @operator: An (optional) operator, appended after adding the first arg
> + * @separator: An (optional) separator, appended after adding the second arg
> + *
> + * Initialize a dynevent_arg_pair object.  A dynevent_arg_pair
> + * represents an object used to append argument pairs such as 'type
> + * variable_name;' or 'x+y' to the current command string.  An
> + * argument pair consists of a left-hand-side argument and a
> + * right-hand-side argument separated by an operator, which can be
> + * whitespace, all followed by a separator, if applicable. The
> + * @check_arg function, if present, will be used to check the sanity
> + * of the current arg strings (which is directly set by the caller).
> + * After the first arg string is successfully appended to the command
> + * string, the optional @operator is appended, followed by the second
> + * arg and and optional @separator.  If no separator was specified
> + * when initializing the arg, a space will be appended.
> + */
> +void dynevent_arg_pair_init(struct dynevent_arg_pair *arg_pair,
> +			    dynevent_check_arg_fn_t check_arg,
> +			    char operator, char separator)
> +{
> +	memset(arg_pair, '\0', sizeof(*arg_pair));
> +
> +	if (!operator)
> +		operator = ' ';
> +	arg_pair->operator = operator;
> +
> +	if (!separator)
> +		separator = ' ';
> +	arg_pair->separator = separator;
> +
> +	arg_pair->check_arg = check_arg;
> +}
> +
> +/**
> + * dynevent_create - Create the dynamic event contained in dynevent_cmd
> + * @cmd: The dynevent_cmd object containing the dynamic event creation command
> + *
> + * Once a dynevent_cmd object has been successfully built up via the
> + * dynevent_cmd_init(), dynevent_arg_add() and dynevent_arg_pair_add()
> + * functions, this function runs the final command to actually create
> + * the event.
> + *
> + * Return: 0 if the event was successfully created, error otherwise.
> + */
> +int dynevent_create(struct dynevent_cmd *cmd)
> +{
> +	return cmd->run_command(cmd);
> +}
> +EXPORT_SYMBOL_GPL(dynevent_create);
> +
>  #ifdef CONFIG_EVENT_TRACE_STARTUP_TEST
>  
>  static DEFINE_SPINLOCK(test_spinlock);
> -- 
> 2.14.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>

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