On Mon, 5 Oct 2020 12:55:14 +0200 SeongJae Park [off-list ref] wrote:

From: SeongJae Park <redacted>

DAMON is designed to be used by kernel space code such as the memory
management subsystems, and therefore it provides only kernel space API.
That said, letting the user space control DAMON could provide some
benefits to them.  For example, it will allow user space to analyze
their specific workloads and make their own special optimizations.

For such cases, this commit implements a simple DAMON application kernel
module, namely 'damon-dbgfs', which merely wraps the DAMON api and
exports those to the user space via the debugfs.

[...]

+
+static ssize_t dbgfs_monitor_on_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	ssize_t ret = count;
+	char *kbuf;
+	int err;
+
+	kbuf = user_input_str(buf, count, ppos);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	/* Remove white space */
+	if (sscanf(kbuf, "%s", kbuf) != 1)
+		return -EINVAL;
+	if (!strncmp(kbuf, "on", count))
+		err = dbgfs_start_ctxs(dbgfs_ctxs, dbgfs_nr_ctxs);
+	else if (!strncmp(kbuf, "off", count))
+		err = damon_stop(dbgfs_ctxs, dbgfs_nr_ctxs);
+	else
+		return -EINVAL;
+
+	if (err)
+		ret = err;
+	return ret;

'kbuf' should be freed before returning from this function.  I will fix it in
the next version.  To find more potential memory leaks, I ran 'kmemleak' after
a set of correctness tests[1], but it didn't find more leaks.

[1] https://github.com/awslabs/damon-tests/tree/master/corr


Thanks,
SeongJae Park