Add METADATA ioctl

[deliverable/lttng-modules.git] / ltt-debugfs-abi.c

diff --git a/ltt-debugfs-abi.c b/ltt-debugfs-abi.c
index 41774e4356a70cbede41747b5067ffd67c64d262..340f7ddc1d685cdace58f4357eece818398e587b 100644 (file)
--- a/ltt-debugfs-abi.c
+++ b/ltt-debugfs-abi.c
@@ -41,8 +41,15 @@ static struct dentry *lttng_dentry;
 static const struct file_operations lttng_fops;
 static const struct file_operations lttng_session_fops;
 static const struct file_operations lttng_channel_fops;
+static const struct file_operations lttng_metadata_fops;
 static const struct file_operations lttng_event_fops;
 
+enum channel_type {
+       PER_CPU_CHANNEL,
+       GLOBAL_CHANNEL,
+       METADATA_CHANNEL,
+};
+
 static
 int lttng_abi_create_session(void)
 {
@@ -107,10 +114,52 @@ static const struct file_operations lttng_fops = {
 #endif
 };
 
+/*
+ * We tolerate no failure in this function (if one happens, we print a dmesg
+ * error, but cannot return any error, because the channel information is
+ * invariant.
+ */
+static
+void lttng_metadata_create_events(struct file *channel_file)
+{
+       struct ltt_channel *channel = channel_file->private_data;
+       char *event_name = "lttng-metadata";
+       struct ltt_event *event;
+       int ret;
+       void *probe;
+
+       probe = ltt_probe_get(event_name);
+       if (!probe) {
+               ret = -ENOENT;
+               goto probe_error;
+       }
+       /*
+        * We tolerate no failure path after event creation. It will stay
+        * invariant for the rest of the session.
+        */
+       event = ltt_event_create(channel, event_name, INSTRUM_TRACEPOINTS,
+                                probe, NULL);
+       if (!event) {
+               goto event_error;
+               ret = -EEXIST;
+       }
+       return;
+
+event_error:
+       ltt_probe_put(probe);
+probe_error:
+       WARN_ON(1);
+       return;         /* not allowed to return error */
+}
+
+static
 int lttng_abi_create_channel(struct file *session_file,
-                            struct lttng_channel __user *uchan_param)
+                            struct lttng_channel __user *uchan_param,
+                            enum channel_type channel_type)
 {
        struct ltt_session *session = session_file->private_data;
+       const struct file_operations *fops;
+       const char *transport_name;
        struct ltt_channel *chan;
        struct file *chan_file;
        struct lttng_channel chan_param;
@@ -131,11 +180,30 @@ int lttng_abi_create_channel(struct file *session_file,
                ret = PTR_ERR(chan_file);
                goto file_error;
        }
+       switch (channel_type) {
+       case PER_CPU_CHANNEL:
+               transport_name = chan_param.overwrite ?
+                       "relay-overwrite" : "relay-discard";
+               fops = &lttng_channel_fops;
+               break;
+       case GLOBAL_CHANNEL:
+               transport_name = chan_param.overwrite ?
+                       "global-relay-overwrite" : "global-relay-discard";
+               fops = &lttng_channel_fops;
+               break;
+       case METADATA_CHANNEL:
+               transport_name = "global-relay-discard";
+               fops = &lttng_metadata_fops;
+               break;
+       default:
+               transport_name = "<unknown>";
+               break;
+       }
        /*
         * We tolerate no failure path after channel creation. It will stay
         * invariant for the rest of the session.
         */
-       chan = ltt_channel_create(session, chan_param.overwrite, NULL,
+       chan = ltt_channel_create(session, transport_name, NULL,
                                  chan_param.subbuf_size,
                                  chan_param.num_subbuf,
                                  chan_param.switch_timer_interval,
@@ -147,6 +215,9 @@ int lttng_abi_create_channel(struct file *session_file,
        chan->file = chan_file;
        chan_file->private_data = chan;
        fd_install(chan_fd, chan_file);
+       if (channel_type == METADATA_CHANNEL)
+               lttng_metadata_create_events(chan_file);
+
        /* The channel created holds a reference on the session */
        atomic_long_inc(&session_file->f_count);
 
@@ -180,11 +251,17 @@ long lttng_session_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
        switch (cmd) {
        case LTTNG_CHANNEL:
-               return lttng_abi_create_channel(file, (struct lttng_channel __user *)arg);
+               return lttng_abi_create_channel(file,
+                               (struct lttng_channel __user *)arg,
+                               PER_CPU_CHANNEL);
        case LTTNG_SESSION_START:
                return ltt_session_start(session);
        case LTTNG_SESSION_STOP:
                return ltt_session_stop(session);
+       case LTTNG_METADATA:
+               return lttng_abi_create_channel(file,
+                               (struct lttng_channel __user *)arg,
+                               METADATA_CHANNEL);
        default:
                return -ENOIOCTLCMD;
        }
@@ -344,7 +421,6 @@ name_error:
  *     LTTNG_EVENT
  *             Returns an event file descriptor or failure.
  *
- * The returned session will be deleted when its file descriptor is closed.
  * Channel and event file descriptors also hold a reference on the session.
  */
 static
@@ -360,6 +436,30 @@ long lttng_channel_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
        }
 }
 
+/**
+ *     lttng_metadata_ioctl - lttng syscall through ioctl
+ *
+ *     @file: the file
+ *     @cmd: the command
+ *     @arg: command arg
+ *
+ *     This ioctl implements lttng commands:
+ *      LTTNG_STREAM
+ *              Returns an event stream file descriptor or failure.
+ *
+ * Channel and event file descriptors also hold a reference on the session.
+ */
+static
+long lttng_metadata_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+       switch (cmd) {
+       case LTTNG_STREAM:
+               return lttng_abi_open_stream(file);
+       default:
+               return -ENOIOCTLCMD;
+       }
+}
+
 /* TODO: poll */
 #if 0
 /**
@@ -410,6 +510,14 @@ static const struct file_operations lttng_channel_fops = {
 #endif
 };
 
+static const struct file_operations lttng_metadata_fops = {
+       .release = lttng_channel_release,
+       .unlocked_ioctl = lttng_metadata_ioctl,
+#ifdef CONFIG_COMPAT
+       .compat_ioctl = lttng_metadata_ioctl,
+#endif
+};
+
 static
 int lttng_event_release(struct inode *inode, struct file *file)
 {