1 files changed, 187 insertions, 0 deletions

diff --git a/drivers/oprofile/event_buffer.c b/drivers/oprofile/event_buffer.c
new file mode 100644
index 000000000000..166bca790133
--- /dev/null
+++ b/drivers/oprofile/event_buffer.c
@@ -0,0 +1,187 @@
+/**
+ * @file event_buffer.c
+ *
+ * @remark Copyright 2002 OProfile authors
+ * @remark Read the file COPYING
+ *
+ * @author John Levon <levon@movementarian.org>
+ *
+ * This is the global event buffer that the user-space
+ * daemon reads from. The event buffer is an untyped array
+ * of unsigned longs. Entries are prefixed by the
+ * escape value ESCAPE_CODE followed by an identifying code.
+ */
+
+#include <linux/vmalloc.h>
+#include <linux/oprofile.h>
+#include <linux/sched.h>
+#include <linux/dcookies.h>
+#include <linux/fs.h>
+#include <asm/uaccess.h>
+ 
+#include "oprof.h"
+#include "event_buffer.h"
+#include "oprofile_stats.h"
+
+DECLARE_MUTEX(buffer_sem);
+ 
+static unsigned long buffer_opened;
+static DECLARE_WAIT_QUEUE_HEAD(buffer_wait);
+static unsigned long * event_buffer;
+static unsigned long buffer_size;
+static unsigned long buffer_watershed;
+static size_t buffer_pos;
+/* atomic_t because wait_event checks it outside of buffer_sem */
+static atomic_t buffer_ready = ATOMIC_INIT(0);
+
+/* Add an entry to the event buffer. When we
+ * get near to the end we wake up the process
+ * sleeping on the read() of the file.
+ */
+void add_event_entry(unsigned long value)
+{
+	if (buffer_pos == buffer_size) {
+		atomic_inc(&oprofile_stats.event_lost_overflow);
+		return;
+	}
+
+	event_buffer[buffer_pos] = value;
+	if (++buffer_pos == buffer_size - buffer_watershed) {
+		atomic_set(&buffer_ready, 1);
+		wake_up(&buffer_wait);
+	}
+}
+
+
+/* Wake up the waiting process if any. This happens
+ * on "echo 0 >/dev/oprofile/enable" so the daemon
+ * processes the data remaining in the event buffer.
+ */
+void wake_up_buffer_waiter(void)
+{
+	down(&buffer_sem);
+	atomic_set(&buffer_ready, 1);
+	wake_up(&buffer_wait);
+	up(&buffer_sem);
+}
+
+ 
+int alloc_event_buffer(void)
+{
+	int err = -ENOMEM;
+
+	spin_lock(&oprofilefs_lock);
+	buffer_size = fs_buffer_size;
+	buffer_watershed = fs_buffer_watershed;
+	spin_unlock(&oprofilefs_lock);
+ 
+	if (buffer_watershed >= buffer_size)
+		return -EINVAL;
+ 
+	event_buffer = vmalloc(sizeof(unsigned long) * buffer_size);
+	if (!event_buffer)
+		goto out; 
+
+	err = 0;
+out:
+	return err;
+}
+
+
+void free_event_buffer(void)
+{
+	vfree(event_buffer);
+}
+
+ 
+static int event_buffer_open(struct inode * inode, struct file * file)
+{
+	int err = -EPERM;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (test_and_set_bit(0, &buffer_opened))
+		return -EBUSY;
+
+	/* Register as a user of dcookies
+	 * to ensure they persist for the lifetime of
+	 * the open event file
+	 */
+	err = -EINVAL;
+	file->private_data = dcookie_register();
+	if (!file->private_data)
+		goto out;
+		 
+	if ((err = oprofile_setup()))
+		goto fail;
+
+	/* NB: the actual start happens from userspace
+	 * echo 1 >/dev/oprofile/enable
+	 */
+ 
+	return 0;
+
+fail:
+	dcookie_unregister(file->private_data);
+out:
+	clear_bit(0, &buffer_opened);
+	return err;
+}
+
+
+static int event_buffer_release(struct inode * inode, struct file * file)
+{
+	oprofile_stop();
+	oprofile_shutdown();
+	dcookie_unregister(file->private_data);
+	buffer_pos = 0;
+	atomic_set(&buffer_ready, 0);
+	clear_bit(0, &buffer_opened);
+	return 0;
+}
+
+
+static ssize_t event_buffer_read(struct file * file, char __user * buf,
+				 size_t count, loff_t * offset)
+{
+	int retval = -EINVAL;
+	size_t const max = buffer_size * sizeof(unsigned long);
+
+	/* handling partial reads is more trouble than it's worth */
+	if (count != max || *offset)
+		return -EINVAL;
+
+	wait_event_interruptible(buffer_wait, atomic_read(&buffer_ready));
+
+	if (signal_pending(current))
+		return -EINTR;
+
+	/* can't currently happen */
+	if (!atomic_read(&buffer_ready))
+		return -EAGAIN;
+
+	down(&buffer_sem);
+
+	atomic_set(&buffer_ready, 0);
+
+	retval = -EFAULT;
+
+	count = buffer_pos * sizeof(unsigned long);
+ 
+	if (copy_to_user(buf, event_buffer, count))
+		goto out;
+
+	retval = count;
+	buffer_pos = 0;
+ 
+out:
+	up(&buffer_sem);
+	return retval;
+}
+ 
+struct file_operations event_buffer_fops = {
+	.open		= event_buffer_open,
+	.release	= event_buffer_release,
+	.read		= event_buffer_read,
+};