Commit 6edb2a8a authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

tracing: Clean up tracing_mark_write() 



On gcc 4.5 the function tracing_mark_write() would give a warning
of page2 being uninitialized. This is due to a bug in gcc because
the logic prevents page2 from being used uninitialized, and
gcc 4.6+ does not complain (correctly).

Instead of adding a "unitialized" around page2, which could show
a bug later on, I combined page1 and page2 into an array map_pages[].
This binds the two and the two are modified according to nr_pages
(what gcc 4.5 seems to ignore). This no longer gives a warning with
gcc 4.5 nor with gcc 4.6.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 978da300

kernel/trace/trace.c

+11 −13
Original line number Diff line number Diff line
@@ -3875,14 +3875,14 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 
	struct print_entry *entry;

	unsigned long irq_flags;

	struct page *pages[2];

	void *map_page[2];

	int nr_pages = 1;

	ssize_t written;

	void *page1;

	void *page2;

	int offset;

	int size;

	int len;

	int ret;

	int i;



	if (tracing_disabled)

		return -EINVAL;
@@ -3921,9 +3921,8 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 
		goto out;

	}



	page1 = kmap_atomic(pages[0]);

	if (nr_pages == 2)

		page2 = kmap_atomic(pages[1]);

	for (i = 0; i < nr_pages; i++)

		map_page[i] = kmap_atomic(pages[i]);



	local_save_flags(irq_flags);

	size = sizeof(*entry) + cnt + 2; /* possible \n added */
@@ -3941,10 +3940,10 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 


	if (nr_pages == 2) {

		len = PAGE_SIZE - offset;

		memcpy(&entry->buf, page1 + offset, len);

		memcpy(&entry->buf[len], page2, cnt - len);

		memcpy(&entry->buf, map_page[0] + offset, len);

		memcpy(&entry->buf[len], map_page[1], cnt - len);

	} else

		memcpy(&entry->buf, page1 + offset, cnt);

		memcpy(&entry->buf, map_page[0] + offset, cnt);



	if (entry->buf[cnt - 1] != '\n') {

		entry->buf[cnt] = '\n';
@@ -3959,11 +3958,10 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 
	*fpos += written;



 out_unlock:

	if (nr_pages == 2)

		kunmap_atomic(page2);

	kunmap_atomic(page1);

	while (nr_pages > 0)

		put_page(pages[--nr_pages]);

	for (i = 0; i < nr_pages; i++){

		kunmap_atomic(map_page[i]);

		put_page(pages[i]);

	}

 out:

	return written;

}

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