linux-kernel - Re: [PATCH v2 1/4] tracing/dynevent: Delegate parsing to create function

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Date:   Sat, 24 Oct 2020 17:50:40 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Tom Zanussi <zanussi@...nel.org>
Cc:     rostedt@...dmis.org, axelrasmussen@...gle.com, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] tracing/dynevent: Delegate parsing to create
 function

Hi Tom,

Thanks for the update!

On Fri, 23 Oct 2020 15:33:52 -0500
Tom Zanussi <zanussi@...nel.org> wrote:

> From: Masami Hiramatsu <mhiramat@...nel.org>
> 
> Delegate command parsing to each create function so that the
> command syntax can be customized.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> [ zanussi@...nel.org: added synthetic event modifications ]

Since you've customized the synth_event parser, could you update
the patch description? (Or split this into 2 patches)

> Signed-off-by: Tom Zanussi <zanussi@...nel.org>
> ---
>  kernel/trace/trace.c              |  23 +---
>  kernel/trace/trace.h              |   3 +-
>  kernel/trace/trace_dynevent.c     |  35 +++---
>  kernel/trace/trace_dynevent.h     |   4 +-
>  kernel/trace/trace_events_synth.c | 186 ++++++++++++++++--------------
>  kernel/trace/trace_kprobe.c       |  33 +++---
>  kernel/trace/trace_probe.c        |  17 +++
>  kernel/trace/trace_probe.h        |   1 +
>  kernel/trace/trace_uprobe.c       |  17 ++-
>  9 files changed, 174 insertions(+), 145 deletions(-)

[..]
> @@ -1223,26 +1176,43 @@ static int __create_synth_event(int argc, const char *name, const char **argv)
>  		goto out;
>  	}
>  
> -	for (i = 0; i < argc - 1; i++) {
> -		if (strcmp(argv[i], ";") == 0)
> -			continue;
> +	tmp_fields = saved_fields = kstrdup(raw_fields, GFP_KERNEL);
> +	if (!tmp_fields) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	while ((field_str = strsep(&tmp_fields, ";")) != NULL) {
>  		if (n_fields == SYNTH_FIELDS_MAX) {
>  			synth_err(SYNTH_ERR_TOO_MANY_FIELDS, 0);
>  			ret = -EINVAL;
>  			goto err;
>  		}
>  
> -		field = parse_synth_field(argc - i, &argv[i], &consumed);
> +		argv = argv_split(GFP_KERNEL, field_str, &argc);
> +		if (!argv) {
> +			ret = -ENOMEM;
> +			goto err;
> +		}
> +
> +		if (!argc)
> +			continue;
> +
> +		field = parse_synth_field(argc, argv);
>  		if (IS_ERR(field)) {
> +			argv_free(argv);
>  			ret = PTR_ERR(field);
>  			goto err;
>  		}
> +
> +		argv_free(argv);
> +
>  		fields[n_fields++] = field;
>  		i += consumed - 1;

You may not need this line (and "consumed") anymore?

>  	}
>  
> -	if (i < argc && strcmp(argv[i], ";") != 0) {
> -		synth_err(SYNTH_ERR_INVALID_FIELD, errpos(argv[i]));
> +	if (n_fields == 0) {
> +		synth_err(SYNTH_ERR_CMD_INCOMPLETE, 0);
>  		ret = -EINVAL;
>  		goto err;
>  	}
> @@ -1261,6 +1231,8 @@ static int __create_synth_event(int argc, const char *name, const char **argv)
>   out:
>  	mutex_unlock(&event_mutex);
>  
> +	kfree(saved_fields);
> +
>  	return ret;
>   err:
>  	for (i = 0; i < n_fields; i++)
> @@ -1378,18 +1350,35 @@ int synth_event_delete(const char *event_name)
>  }
>  EXPORT_SYMBOL_GPL(synth_event_delete);
>  
> -static int create_or_delete_synth_event(int argc, char **argv)
> +static int create_or_delete_synth_event(const char *raw_command)
>  {
> -	const char *name = argv[0];
> -	int ret;
> +	char **argv, *name = NULL, *fields;
> +	int argc = 0, ret = 0;
> +
> +	last_cmd_set(raw_command);
> +
> +	argv = argv_split(GFP_KERNEL, raw_command, &argc);
> +	if (!argv)
> +		return -ENOMEM;

If you are sure the first argument is the name, you don't need
to use argv_split, but just strpbrk(raw_command, " \t"), something
like this.

	raw_command = skip_spaces(raw_command);
	p = strpbrk(raw_command, " \t");
	if (!p)
		return -EINVAL;

	name = kmemdup_nul(raw_command, p - raw_command, GFP_KERNEL);
	field = skip_spaces(p);

...

	ret = __create_synth_event(name, fields);
free:
	kfree(name);

(BTW, we should have find_spaces() instead of slow strpbrk().)


Thank you,


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