Re: [PATCH v6 2/6] tracing: Rework synthetic event command parsing

[Masami Hiramatsu]

On Thu, 21 Jan 2021 11:01:05 -0600
Tom Zanussi <zanussi@xxxxxxxxxx> wrote:

> Now that command parsing has been delegated to the create functions
> and we're no longer constrained by argv_split(), we can modify the
> synthetic event command parser to better match the higher-level
> structure of the synthetic event commands, which is basically an event
> name followed by a set of semicolon-separated fields.
> 
> Since we're also now passed the raw command, we can also save it
> directly and can get rid of save_cmdstr().
> 

This looks good to me.

Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

Thank you,

> Signed-off-by: Tom Zanussi <zanussi@xxxxxxxxxx>
> ---
>  kernel/trace/trace_events_synth.c | 198 +++++++++++++++---------------
>  1 file changed, 98 insertions(+), 100 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
> index b2588a5650c9..a79c17b97add 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -48,7 +48,7 @@ static int errpos(const char *str)
>  	return err_pos(last_cmd, str);
>  }
>  
> -static void last_cmd_set(char *str)
> +static void last_cmd_set(const char *str)
>  {
>  	if (!str)
>  		return;
> @@ -579,18 +579,14 @@ static void free_synth_field(struct synth_field *field)
>  	kfree(field);
>  }
>  
> -static struct synth_field *parse_synth_field(int argc, const char **argv,
> -					     int *consumed)
> +static struct synth_field *parse_synth_field(int argc, char **argv)
>  {
> -	struct synth_field *field;
>  	const char *prefix = NULL, *field_type = argv[0], *field_name, *array;
> -	int len, ret = -ENOMEM;
> +	int len, consumed, ret = -ENOMEM;
> +	struct synth_field *field;
>  	struct seq_buf s;
>  	ssize_t size;
>  
> -	if (field_type[0] == ';')
> -		field_type++;
> -
>  	if (!strcmp(field_type, "unsigned")) {
>  		if (argc < 3) {
>  			synth_err(SYNTH_ERR_INCOMPLETE_TYPE, errpos(field_type));
> @@ -599,10 +595,20 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
>  		prefix = "unsigned ";
>  		field_type = argv[1];
>  		field_name = argv[2];
> -		*consumed = 3;
> +		consumed = 3;
>  	} else {
>  		field_name = argv[1];
> -		*consumed = 2;
> +		consumed = 2;
> +	}
> +
> +	if (consumed < argc) {
> +		synth_err(SYNTH_ERR_INVALID_FIELD, errpos(field_type));
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	if (!field_name) {
> +		synth_err(SYNTH_ERR_INVALID_FIELD, errpos(field_type));
> +		return ERR_PTR(-EINVAL);
>  	}
>  
>  	field = kzalloc(sizeof(*field), GFP_KERNEL);
> @@ -613,8 +619,6 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
>  	array = strchr(field_name, '[');
>  	if (array)
>  		len -= strlen(array);
> -	else if (field_name[len - 1] == ';')
> -		len--;
>  
>  	field->name = kmemdup_nul(field_name, len, GFP_KERNEL);
>  	if (!field->name)
> @@ -626,8 +630,6 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
>  		goto free;
>  	}
>  
> -	if (field_type[0] == ';')
> -		field_type++;
>  	len = strlen(field_type) + 1;
>  
>  	if (array)
> @@ -644,11 +646,8 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
>  	if (prefix)
>  		seq_buf_puts(&s, prefix);
>  	seq_buf_puts(&s, field_type);
> -	if (array) {
> +	if (array)
>  		seq_buf_puts(&s, array);
> -		if (s.buffer[s.len - 1] == ';')
> -			s.len--;
> -	}
>  	if (WARN_ON_ONCE(!seq_buf_buffer_left(&s)))
>  		goto free;
>  
> @@ -1160,46 +1159,12 @@ int synth_event_gen_cmd_array_start(struct dynevent_cmd *cmd, const char *name,
>  }
>  EXPORT_SYMBOL_GPL(synth_event_gen_cmd_array_start);
>  
> -static int save_cmdstr(int argc, const char *name, const char **argv)
> -{
> -	struct seq_buf s;
> -	char *buf;
> -	int i;
> -
> -	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
> -	if (!buf)
> -		return -ENOMEM;
> -
> -	seq_buf_init(&s, buf, MAX_DYNEVENT_CMD_LEN);
> -
> -	seq_buf_puts(&s, name);
> -
> -	for (i = 0; i < argc; i++) {
> -		seq_buf_putc(&s, ' ');
> -		seq_buf_puts(&s, argv[i]);
> -	}
> -
> -	if (!seq_buf_buffer_left(&s)) {
> -		synth_err(SYNTH_ERR_CMD_TOO_LONG, 0);
> -		kfree(buf);
> -		return -EINVAL;
> -	}
> -	buf[s.len] = 0;
> -	last_cmd_set(buf);
> -
> -	kfree(buf);
> -	return 0;
> -}
> -
> -static int __create_synth_event(int argc, const char *name, const char **argv)
> +static int __create_synth_event(const char *name, const char *raw_fields)
>  {
> +	char **argv, *field_str, *tmp_fields, *saved_fields = NULL;
>  	struct synth_field *field, *fields[SYNTH_FIELDS_MAX];
> +	int i, argc, n_fields = 0, ret = 0;
>  	struct synth_event *event = NULL;
> -	int i, consumed = 0, n_fields = 0, ret = 0;
> -
> -	ret = save_cmdstr(argc, name, argv);
> -	if (ret)
> -		return ret;
>  
>  	/*
>  	 * Argument syntax:
> @@ -1208,13 +1173,14 @@ static int __create_synth_event(int argc, const char *name, const char **argv)
>  	 *      where 'field' = type field_name
>  	 */
>  
> -	if (name[0] == '\0' || argc < 1) {
> +	mutex_lock(&event_mutex);
> +
> +	if (name[0] == '\0') {
>  		synth_err(SYNTH_ERR_CMD_INCOMPLETE, 0);
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto out;
>  	}
>  
> -	mutex_lock(&event_mutex);
> -
>  	if (!is_good_name(name)) {
>  		synth_err(SYNTH_ERR_BAD_NAME, errpos(name));
>  		ret = -EINVAL;
> @@ -1228,26 +1194,41 @@ 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;
> -		if (n_fields == SYNTH_FIELDS_MAX) {
> -			synth_err(SYNTH_ERR_TOO_MANY_FIELDS, 0);
> -			ret = -EINVAL;
> +	tmp_fields = saved_fields = kstrdup(raw_fields, GFP_KERNEL);
> +	if (!tmp_fields) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	while ((field_str = strsep(&tmp_fields, ";")) != NULL) {
> +		argv = argv_split(GFP_KERNEL, field_str, &argc);
> +		if (!argv) {
> +			ret = -ENOMEM;
>  			goto err;
>  		}
>  
> -		field = parse_synth_field(argc - i, &argv[i], &consumed);
> +		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;
> +		if (n_fields == SYNTH_FIELDS_MAX) {
> +			synth_err(SYNTH_ERR_TOO_MANY_FIELDS, 0);
> +			ret = -EINVAL;
> +			goto err;
> +		}
>  	}
>  
> -	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;
>  	}
> @@ -1266,6 +1247,8 @@ 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++)
> @@ -1385,29 +1368,38 @@ EXPORT_SYMBOL_GPL(synth_event_delete);
>  
>  static int create_or_delete_synth_event(const char *raw_command)
>  {
> -	char **argv, *name = NULL;
> -	int argc = 0, ret = 0;
> +	char *name = NULL, *fields, *p;
> +	int ret = 0;
>  
> -	argv = argv_split(GFP_KERNEL, raw_command, &argc);
> -	if (!argv)
> -		return -ENOMEM;
> +	raw_command = skip_spaces(raw_command);
> +	if (raw_command[0] == '\0')
> +		return ret;
> +
> +	last_cmd_set(raw_command);
>  
> -	if (!argc)
> +	p = strpbrk(raw_command, " \t");
> +	if (!p && raw_command[0] != '!') {
> +		synth_err(SYNTH_ERR_CMD_INCOMPLETE, 0);
> +		ret = -EINVAL;
>  		goto free;
> +	}
>  
> -	name = argv[0];
> +	name = kmemdup_nul(raw_command, p ? p - raw_command : strlen(raw_command), GFP_KERNEL);
> +	if (!name)
> +		return -ENOMEM;
>  
> -	/* trace_run_command() ensures argc != 0 */
>  	if (name[0] == '!') {
>  		ret = synth_event_delete(name + 1);
>  		goto free;
>  	}
>  
> -	ret = __create_synth_event(argc - 1, name, (const char **)argv + 1);
> +	fields = skip_spaces(p);
> +
> +	ret = __create_synth_event(name, fields);
>  free:
> -	argv_free(argv);
> +	kfree(name);
>  
> -	return ret == -ECANCELED ? -EINVAL : ret;
> +	return ret;
>  }
>  
>  static int synth_event_run_command(struct dynevent_cmd *cmd)
> @@ -1953,39 +1945,45 @@ EXPORT_SYMBOL_GPL(synth_event_trace_end);
>  
>  static int create_synth_event(const char *raw_command)
>  {
> -	char **argv, *name;
> -	int len, argc = 0, ret = 0;
> +	char *fields, *p;
> +	const char *name;
> +	int len, ret = 0;
>  
> -	argv = argv_split(GFP_KERNEL, raw_command, &argc);
> -	if (!argv) {
> -		ret = -ENOMEM;
> +	raw_command = skip_spaces(raw_command);
> +	if (raw_command[0] == '\0')
>  		return ret;
> -	}
>  
> -	if (!argc)
> -		goto free;
> +	last_cmd_set(raw_command);
>  
> -	name = argv[0];
> +	p = strpbrk(raw_command, " \t");
> +	if (!p)
> +		return -EINVAL;
>  
> -	if (name[0] != 's' || name[1] != ':') {
> -		ret = -ECANCELED;
> -		goto free;
> -	}
> +	fields = skip_spaces(p);
> +
> +	name = raw_command;
> +
> +	if (name[0] != 's' || name[1] != ':')
> +		return -ECANCELED;
>  	name += 2;
>  
>  	/* This interface accepts group name prefix */
>  	if (strchr(name, '/')) {
>  		len = str_has_prefix(name, SYNTH_SYSTEM "/");
> -		if (len == 0) {
> -			ret = -EINVAL;
> -			goto free;
> -		}
> +		if (len == 0)
> +			return -EINVAL;
>  		name += len;
>  	}
>  
> -	ret = __create_synth_event(argc - 1, name, (const char **)argv + 1);
> -free:
> -	argv_free(argv);
> +	len = name - raw_command;
> +
> +	name = kmemdup_nul(raw_command + len, p - raw_command - len, GFP_KERNEL);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	ret = __create_synth_event(name, fields);
> +
> +	kfree(name);
>  
>  	return ret;
>  }
> -- 
> 2.17.1
> 


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>