perf_event: remove redundant zero fill

From: Márton Németh <[email protected]>

The buffer is first zeroed out by memset(). Then strncpy() is used to fill the content. The strncpy() function also pads the string till the end of the specified length, which is redundant. The strncpy() does not ensures that the string will be properly closed with 0. Use strlcpy() instead.

The semantic match that finds this kind of pattern is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression buffer;
expression size;
expression str;
@@

	memset(buffer, 0, size);
	...
-	strncpy(
+	strlcpy(
	buffer, str, sizeof(buffer)
	);

@@
expression buffer;
expression size;
expression str;
@@

	memset(&buffer, 0, size);
	...
-	strncpy(
+	strlcpy(
	&buffer, str, sizeof(buffer));

@@
expression buffer;
identifier field;
expression size;
expression str;
@@

	memset(buffer, 0, size);
	...
-	strncpy(
+	strlcpy(
	buffer->field, str, sizeof(buffer->field)
	);

@@
expression buffer;
identifier field;
expression size;
expression str;
@@

	memset(&buffer, 0, size);
	...
-	strncpy(
+	strlcpy(
	buffer.field, str, sizeof(buffer.field));

// </smpl>

On strncpy() vs strlcpy() see http://www.gratisoft.us/todd/papers/strlcpy.html .

---

diff -u -p a/kernel/perf_event.c b/kernel/perf_event.c
@@ -3367,7 +3367,7 @@ static void perf_event_comm_event(struct
 	char comm[TASK_COMM_LEN];
 
 	memset(comm, 0, sizeof(comm));
-	strncpy(comm, comm_event->task->comm, sizeof(comm));
+	strlcpy(comm, comm_event->task->comm, sizeof(comm));
 	size = ALIGN(strlen(comm)+1, sizeof(u64));
 
 	comm_event->comm = comm;