1 files changed, 107 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 10d5503f0d04..f3c13d63d064 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -352,6 +352,59 @@ static void wakeup_work_handler(struct work_struct *work)
 static DECLARE_DELAYED_WORK(wakeup_work, wakeup_work_handler);
 
 /**
+ * tracing_on - enable tracing buffers
+ *
+ * This function enables tracing buffers that may have been
+ * disabled with tracing_off.
+ */
+void tracing_on(void)
+{
+        if (global_trace.buffer)
+                ring_buffer_record_on(global_trace.buffer);
+        /*
+         * This flag is only looked at when buffers haven't been
+         * allocated yet. We don't really care about the race
+         * between setting this flag and actually turning
+         * on the buffer.
+         */
+        global_trace.buffer_disabled = 0;
+}
+EXPORT_SYMBOL_GPL(tracing_on);
+
+/**
+ * tracing_off - turn off tracing buffers
+ *
+ * This function stops the tracing buffers from recording data.
+ * It does not disable any overhead the tracers themselves may
+ * be causing. This function simply causes all recording to
+ * the ring buffers to fail.
+ */
+void tracing_off(void)
+{
+        if (global_trace.buffer)
+                ring_buffer_record_on(global_trace.buffer);
+        /*
+         * This flag is only looked at when buffers haven't been
+         * allocated yet. We don't really care about the race
+         * between setting this flag and actually turning
+         * on the buffer.
+         */
+        global_trace.buffer_disabled = 1;
+}
+EXPORT_SYMBOL_GPL(tracing_off);
+
+/**
+ * tracing_is_on - show state of ring buffers enabled
+ */
+int tracing_is_on(void)
+{
+        if (global_trace.buffer)
+                return ring_buffer_record_is_on(global_trace.buffer);
+        return !global_trace.buffer_disabled;
+}
+EXPORT_SYMBOL_GPL(tracing_is_on);
+
+/**
  * trace_wake_up - wake up tasks waiting for trace input
  *
  * Schedules a delayed work to wake up any task that is blocked on the
@@ -4567,6 +4620,55 @@ static __init void create_trace_options_dir(void)
                 create_trace_option_core_file(trace_options[i], i);
 }
 
+static ssize_t
+rb_simple_read(struct file *filp, char __user *ubuf,
+               size_t cnt, loff_t *ppos)
+{
+        struct ring_buffer *buffer = filp->private_data;
+        char buf[64];
+        int r;
+
+        if (buffer)
+                r = ring_buffer_record_is_on(buffer);
+        else
+                r = 0;
+
+        r = sprintf(buf, "%d\n", r);
+
+        return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+rb_simple_write(struct file *filp, const char __user *ubuf,
+                size_t cnt, loff_t *ppos)
+{
+        struct ring_buffer *buffer = filp->private_data;
+        unsigned long val;
+        int ret;
+
+        ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
+        if (ret)
+                return ret;
+
+        if (buffer) {
+                if (val)
+                        ring_buffer_record_on(buffer);
+                else
+                        ring_buffer_record_off(buffer);
+        }
+
+        (*ppos)++;
+
+        return cnt;
+}
+
+static const struct file_operations rb_simple_fops = {
+        .open           = tracing_open_generic,
+        .read           = rb_simple_read,
+        .write          = rb_simple_write,
+        .llseek         = default_llseek,
+};
+
 static __init int tracer_init_debugfs(void)
 {
         struct dentry *d_tracer;
@@ -4626,6 +4728,9 @@ static __init int tracer_init_debugfs(void)
         trace_create_file("trace_clock", 0644, d_tracer, NULL,
                           &trace_clock_fops);
 
+        trace_create_file("tracing_on", 0644, d_tracer,
+                            global_trace.buffer, &rb_simple_fops);
+
 #ifdef CONFIG_DYNAMIC_FTRACE
         trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
                         &ftrace_update_tot_cnt, &tracing_dyn_info_fops);
@@ -4863,6 +4968,8 @@ __init static int tracer_alloc_buffers(void)
                 goto out_free_cpumask;
         }
         global_trace.entries = ring_buffer_size(global_trace.buffer);
+        if (global_trace.buffer_disabled)
+                tracing_off();
 
 
 #ifdef CONFIG_TRACER_MAX_TRACE