tracing: make event directory structure

This patch adds the directory /debug/tracing/events/ that will contain
all the registered trace points.

 # ls /debug/tracing/events/
sched_kthread_stop      sched_process_fork  sched_switch
sched_kthread_stop_ret  sched_process_free  sched_wait_task
sched_migrate_task      sched_process_wait  sched_wakeup
sched_process_exit      sched_signal_send   sched_wakeup_new

 # ls /debug/tracing/events/sched_switch/
enable

 # cat /debug/tracing/events/sched_switch/enable
1

 # cat /debug/tracing/set_event
sched_switch

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 132 insertions, 5 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 05bc80ec8d2c..3bcb9df93342 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -12,6 +12,11 @@
 
 #include "trace_events.h"
 
+#define events_for_each(event)                                          \
+        for (event = __start_ftrace_events;                             \
+             (unsigned long)event < (unsigned long)__stop_ftrace_events; \
+             event++)
+
 void event_trace_printk(unsigned long ip, const char *fmt, ...)
 {
         va_list ap;
@@ -39,15 +44,16 @@ static void ftrace_clear_events(void)
 
 static int ftrace_set_clr_event(char *buf, int set)
 {
-        struct ftrace_event_call *call = (void *)__start_ftrace_events;
+        struct ftrace_event_call *call = __start_ftrace_events;
 
 
-        while ((unsigned long)call < (unsigned long)__stop_ftrace_events) {
+        events_for_each(call) {
 
-                if (strcmp(buf, call->name) != 0) {
-                        call++;
+                if (!call->name)
+                        continue;
+
+                if (strcmp(buf, call->name) != 0)
                         continue;
-                }
 
                 if (set) {
                         /* Already set? */
@@ -223,6 +229,67 @@ ftrace_event_seq_open(struct inode *inode, struct file *file)
         return ret;
 }
 
+static ssize_t
+event_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
+                  loff_t *ppos)
+{
+        struct ftrace_event_call *call = filp->private_data;
+        char *buf;
+
+        if (call->enabled)
+                buf = "1\n";
+        else
+                buf = "0\n";
+
+        return simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);
+}
+
+static ssize_t
+event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
+                   loff_t *ppos)
+{
+        struct ftrace_event_call *call = filp->private_data;
+        char buf[64];
+        unsigned long val;
+        int ret;
+
+        if (cnt >= sizeof(buf))
+                return -EINVAL;
+
+        if (copy_from_user(&buf, ubuf, cnt))
+                return -EFAULT;
+
+        buf[cnt] = 0;
+
+        ret = strict_strtoul(buf, 10, &val);
+        if (ret < 0)
+                return ret;
+
+        switch (val) {
+        case 0:
+                if (!call->enabled)
+                        break;
+
+                call->enabled = 0;
+                call->unregfunc();
+                break;
+        case 1:
+                if (call->enabled)
+                        break;
+
+                call->enabled = 1;
+                call->regfunc();
+                break;
+
+        default:
+                return -EINVAL;
+        }
+
+        *ppos += cnt;
+
+        return cnt;
+}
+
 static const struct seq_operations show_event_seq_ops = {
         .start = t_start,
         .next = t_next,
@@ -252,10 +319,59 @@ static const struct file_operations ftrace_set_event_fops = {
         .release = seq_release,
 };
 
+static const struct file_operations ftrace_enable_fops = {
+        .open = tracing_open_generic,
+        .read = event_enable_read,
+        .write = event_enable_write,
+};
+
+static struct dentry *event_trace_events_dir(void)
+{
+        static struct dentry *d_tracer;
+        static struct dentry *d_events;
+
+        if (d_events)
+                return d_events;
+
+        d_tracer = tracing_init_dentry();
+        if (!d_tracer)
+                return NULL;
+
+        d_events = debugfs_create_dir("events", d_tracer);
+        if (!d_events)
+                pr_warning("Could not create debugfs "
+                           "'events' directory\n");
+
+        return d_events;
+}
+
+static int
+event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
+{
+        struct dentry *entry;
+
+        call->dir = debugfs_create_dir(call->name, d_events);
+        if (!call->dir) {
+                pr_warning("Could not create debugfs "
+                           "'%s' directory\n", call->name);
+                return -1;
+        }
+
+        entry = debugfs_create_file("enable", 0644, call->dir, call,
+                                    &ftrace_enable_fops);
+        if (!entry)
+                pr_warning("Could not create debugfs "
+                           "'%s/enable' entry\n", call->name);
+
+        return 0;
+}
+
 static __init int event_trace_init(void)
 {
+        struct ftrace_event_call *call = __start_ftrace_events;
         struct dentry *d_tracer;
         struct dentry *entry;
+        struct dentry *d_events;
 
         d_tracer = tracing_init_dentry();
         if (!d_tracer)
@@ -275,6 +391,17 @@ static __init int event_trace_init(void)
                 pr_warning("Could not create debugfs "
                            "'set_event' entry\n");
 
+        d_events = event_trace_events_dir();
+        if (!d_events)
+                return 0;
+
+        events_for_each(call) {
+                /* The linker may leave blanks */
+                if (!call->name)
+                        continue;
+                event_create_dir(call, d_events);
+        }
+
         return 0;
 }
 fs_initcall(event_trace_init);