Re: [PATCH v3 04/12] tracing: Add dynamic event command creation interface

[Tom Zanussi <zanussi@kernel.org>]

Hi Masami,

On Mon, 2020-01-27 at 22:44 +0900, Masami Hiramatsu wrote:
> Hi Tom,
> 
> On Fri, 24 Jan 2020 16:56:15 -0600
> Tom Zanussi <zanussi@kernel.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 ?
> 

I put this code in trace_events.c since it's about dynamic trace
events, but I agree it would be nicer to have it in separate files. 
I'll move them there in the next version.

Thanks,

Tom

> Thank you,
> 
> > 
> > Signed-off-by: Tom Zanussi <zanussi@kernel.org>
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.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
> > 
> 
>