tracing/uprobe: Add multi-probe per uprobe event support

Allow user to define several probes on one uprobe event.
Note that this only support appending method. So deleting
event will delete all probes on the event.

Link: http://lkml.kernel.org/r/156095687876.28024.13840331032234992863.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

2 files changed, 43 insertions, 19 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a8505d84b76e..c7797a81a37e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4823,7 +4823,7 @@ static const char readme_msg[] =
 	"\t\t\t  Write into this file to define/undefine new trace events.\n"
 #endif
 #ifdef CONFIG_UPROBE_EVENTS
-	"  uprobe_events\t\t- Add/remove/show the userspace dynamic events\n"
+	"  uprobe_events\t\t- Create/append/remove/show the userspace dynamic events\n"
 	"\t\t\t  Write into this file to define/undefine new trace events.\n"
 #endif
 #if defined(CONFIG_KPROBE_EVENTS) || defined(CONFIG_UPROBE_EVENTS)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 2862e6829e48..d84e09abb8de 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -364,15 +364,32 @@ static int unregister_trace_uprobe(struct trace_uprobe *tu)
 {
 	int ret;
 
+	if (trace_probe_has_sibling(&tu->tp))
+		goto unreg;
+
 	ret = unregister_uprobe_event(tu);
 	if (ret)
 		return ret;
 
+unreg:
 	dyn_event_remove(&tu->devent);
+	trace_probe_unlink(&tu->tp);
 	free_trace_uprobe(tu);
 	return 0;
 }
 
+static int append_trace_uprobe(struct trace_uprobe *tu, struct trace_uprobe *to)
+{
+	int ret;
+
+	/* Append to existing event */
+	ret = trace_probe_append(&tu->tp, &to->tp);
+	if (!ret)
+		dyn_event_add(&tu->devent);
+
+	return ret;
+}
+
 /*
  * Uprobe with multiple reference counter is not allowed. i.e.
  * If inode and offset matches, reference counter offset *must*
@@ -382,25 +399,21 @@ static int unregister_trace_uprobe(struct trace_uprobe *tu)
  * as the new one does not conflict with any other existing
  * ones.
  */
-static struct trace_uprobe *find_old_trace_uprobe(struct trace_uprobe *new)
+static int validate_ref_ctr_offset(struct trace_uprobe *new)
 {
 	struct dyn_event *pos;
-	struct trace_uprobe *tmp, *old = NULL;
+	struct trace_uprobe *tmp;
 	struct inode *new_inode = d_real_inode(new->path.dentry);
 
-	old = find_probe_event(trace_probe_name(&new->tp),
-				trace_probe_group_name(&new->tp));
-
 	for_each_trace_uprobe(tmp, pos) {
-		if ((old ? old != tmp : true) &&
-		    new_inode == d_real_inode(tmp->path.dentry) &&
+		if (new_inode == d_real_inode(tmp->path.dentry) &&
 		    new->offset == tmp->offset &&
 		    new->ref_ctr_offset != tmp->ref_ctr_offset) {
 			pr_warn("Reference counter offset mismatch.");
-			return ERR_PTR(-EINVAL);
+			return -EINVAL;
 		}
 	}
-	return old;
+	return 0;
 }
 
 /* Register a trace_uprobe and probe_event */
@@ -411,18 +424,29 @@ static int register_trace_uprobe(struct trace_uprobe *tu)
 
 	mutex_lock(&event_mutex);
 
-	/* register as an event */
-	old_tu = find_old_trace_uprobe(tu);
-	if (IS_ERR(old_tu)) {
-		ret = PTR_ERR(old_tu);
+	ret = validate_ref_ctr_offset(tu);
+	if (ret)
 		goto end;
-	}
 
+	/* register as an event */
+	old_tu = find_probe_event(trace_probe_name(&tu->tp),
+				  trace_probe_group_name(&tu->tp));
 	if (old_tu) {
-		/* delete old event */
-		ret = unregister_trace_uprobe(old_tu);
-		if (ret)
-			goto end;
+		if (is_ret_probe(tu) != is_ret_probe(old_tu)) {
+			trace_probe_log_set_index(0);
+			trace_probe_log_err(0, DIFF_PROBE_TYPE);
+			ret = -EEXIST;
+		} else {
+			ret = trace_probe_compare_arg_type(&tu->tp, &old_tu->tp);
+			if (ret) {
+				/* Note that argument starts index = 2 */
+				trace_probe_log_set_index(ret + 1);
+				trace_probe_log_err(0, DIFF_ARG_TYPE);
+				ret = -EEXIST;
+			} else
+				ret = append_trace_uprobe(tu, old_tu);
+		}
+		goto end;
 	}
 
 	ret = register_uprobe_event(tu);