--- /dev/null
+/**
+ * @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/capability.h>
+#include <linux/dcookies.h>
+#include <linux/fs.h>
+#include <asm/uaccess.h>
+
+#include "oprof.h"
+#include "event_buffer.h"
+#include "oprofile_stats.h"
+
+DEFINE_MUTEX(buffer_mutex);
+
+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_mutex */
+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. To protect
+ * the event_buffer this function may only be called when buffer_mutex
+ * is set.
+ */
+void add_event_entry(unsigned long value)
+{
+ /*
+ * This shouldn't happen since all workqueues or handlers are
+ * canceled or flushed before the event buffer is freed.
+ */
+ if (!event_buffer) {
+ WARN_ON_ONCE(1);
+ return;
+ }
+
+ 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)
+{
+ mutex_lock(&buffer_mutex);
+ atomic_set(&buffer_ready, 1);
+ wake_up(&buffer_wait);
+ mutex_unlock(&buffer_mutex);
+}
+
+
+int alloc_event_buffer(void)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&oprofilefs_lock, flags);
+ buffer_size = oprofile_buffer_size;
+ buffer_watershed = oprofile_buffer_watershed;
+ raw_spin_unlock_irqrestore(&oprofilefs_lock, flags);
+
+ if (buffer_watershed >= buffer_size)
+ return -EINVAL;
+
+ buffer_pos = 0;
+ event_buffer = vmalloc(sizeof(unsigned long) * buffer_size);
+ if (!event_buffer)
+ return -ENOMEM;
+
+ return 0;
+}
+
+
+void free_event_buffer(void)
+{
+ mutex_lock(&buffer_mutex);
+ vfree(event_buffer);
+ buffer_pos = 0;
+ event_buffer = NULL;
+ mutex_unlock(&buffer_mutex);
+}
+
+
+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_lock(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 nonseekable_open(inode, file);
+
+fail:
+ dcookie_unregister(file->private_data);
+out:
+ __clear_bit_unlock(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_unlock(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;
+
+ mutex_lock(&buffer_mutex);
+
+ /* May happen if the buffer is freed during pending reads. */
+ if (!event_buffer) {
+ retval = -EINTR;
+ goto out;
+ }
+
+ 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:
+ mutex_unlock(&buffer_mutex);
+ return retval;
+}
+
+const struct file_operations event_buffer_fops = {
+ .open = event_buffer_open,
+ .release = event_buffer_release,
+ .read = event_buffer_read,
+ .llseek = no_llseek,
+};
Code Review / kvmfornfv.git / blobdiff