linux-kernel - Re: [PATCH v2 4/7] tracing: Add synthetic event error logging

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Date:   Mon, 12 Oct 2020 18:04:39 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Tom Zanussi <zanussi@...nel.org>
Cc:     axelrasmussen@...gle.com, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/7] tracing: Add synthetic event error logging

On Mon, 12 Oct 2020 15:18:06 -0500
Tom Zanussi <zanussi@...nel.org> wrote:

> +static int cmdstr_append(char *buf, const char *str, int *remaining)
> +{
> +	int len = strlen(str);
> +
> +	if (len + 1 >= *remaining) {
> +		synth_err(SYNTH_ERR_CMD_TOO_LONG, 0);
> +		return -EINVAL;
> +	}
> +
> +	strcat(buf, str);
> +	strcat(buf, " ");
> +	*remaining -= len + 1;
> +
> +	return 0;
> +}
> +
> +static int save_cmdstr(int argc, const char *name, const char **argv)
> +{
> +	int i, ret, remaining = MAX_DYNEVENT_CMD_LEN;
> +	char *buf;
> +
> +	synth_err_clear();
> +
> +	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	ret = cmdstr_append(buf, name, &remaining);
> +	if (ret) {
> +		kfree(buf);
> +		return ret;
> +	}
> +
> +	for (i = 0; i < argc; i++) {
> +		ret = cmdstr_append(buf, argv[i], &remaining);
> +		if (ret) {
> +			kfree(buf);
> +			return ret;
> +		}
> +	}
> +
> +	last_cmd_set(buf);
> +
> +	kfree(buf);
> +
> +	return ret;
> +}
> +

Hmm, the above could easily be replaced with:

	struct seq_buf s;

	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;


-- Steve