ANDROID: fix ABI breakage for trace_array extensions

To avoid breaking the ABI, we change trace_array_get_by_name() back to
original API and introduce the new extension API
trace_array_get_by_name_ext() and a wrapper struct trace_array_ext to
support creating instances with specified system events.

Bug: 418940629
Change-Id: I197b52af15d41b3ab56a5d94172cfa532d24ee4b
Signed-off-by: Richard Chang <richardycc@google.com>

drivers/scsi/qla2xxx/qla_os.c

@@ -2883,7 +2883,7 @@ static void qla2x00_iocb_work_fn(struct work_struct *work)
 static void
 qla_trace_init(void)
 {
-	qla_trc_array = trace_array_get_by_name("qla2xxx", NULL);
+	qla_trc_array = trace_array_get_by_name("qla2xxx");
 	if (!qla_trc_array) {
 		ql_log(ql_log_fatal, NULL, 0x0001,
 		       "Unable to create qla2xxx trace instance, instance logging will be disabled.\n");

include/linux/trace.h

@@ -51,7 +51,9 @@ int trace_array_printk(struct trace_array *tr, unsigned long ip,
 		       const char *fmt, ...);
 int trace_array_init_printk(struct trace_array *tr);
 void trace_array_put(struct trace_array *tr);
-struct trace_array *trace_array_get_by_name(const char *name, const char *systems);
+struct trace_array *trace_array_get_by_name(const char *name);
+struct trace_array *trace_array_get_by_name_ext(const char *name,
+						const char *systems);
 int trace_array_destroy(struct trace_array *tr);
 
 /* For osnoise tracer */
@@ -84,7 +86,12 @@ static inline int trace_array_init_printk(struct trace_array *tr)
 static inline void trace_array_put(struct trace_array *tr)
 {
 }
-static inline struct trace_array *trace_array_get_by_name(const char *name, const char *systems)
+static inline struct trace_array *trace_array_get_by_name(const char *name)
+{
+	return NULL;
+}
+static inline struct trace_array *trace_array_get_by_name_ext(
+	const char *name, const char *systems)
 {
 	return NULL;
 }

kernel/trace/trace.c

@@ -9545,14 +9545,16 @@ static int trace_array_create_dir(struct trace_array *tr)
 static struct trace_array *
 trace_array_create_systems(const char *name, const char *systems)
 {
+	struct trace_array_ext *tr_ext;
 	struct trace_array *tr;
 	int ret;
 
 	ret = -ENOMEM;
-	tr = kzalloc(sizeof(*tr), GFP_KERNEL);
-	if (!tr)
+	tr_ext = kzalloc(sizeof(*tr_ext), GFP_KERNEL);
+	if (!tr_ext)
 		return ERR_PTR(ret);
 
+	tr = &tr_ext->trace_array;
 	tr->name = kstrdup(name, GFP_KERNEL);
 	if (!tr->name)
 		goto out_free_tr;
@@ -9564,8 +9566,8 @@ trace_array_create_systems(const char *name, const char *systems)
 		goto out_free_tr;
 
 	if (systems) {
-		tr->system_names = kstrdup_const(systems, GFP_KERNEL);
-		if (!tr->system_names)
+		tr_ext->system_names = kstrdup_const(systems, GFP_KERNEL);
+		if (!tr_ext->system_names)
 			goto out_free_tr;
 	}
 
@@ -9612,9 +9614,9 @@ trace_array_create_systems(const char *name, const char *systems)
 	free_trace_buffers(tr);
 	free_cpumask_var(tr->pipe_cpumask);
 	free_cpumask_var(tr->tracing_cpumask);
-	kfree_const(tr->system_names);
+	kfree_const(tr_ext->system_names);
 	kfree(tr->name);
-	kfree(tr);
+	kfree(tr_ext);
 
 	return ERR_PTR(ret);
 }
@@ -9646,8 +9648,14 @@ out_unlock:
 	return ret;
 }
 
+struct trace_array *trace_array_get_by_name(const char *name)
+{
+	return trace_array_get_by_name_ext(name, NULL);
+}
+EXPORT_SYMBOL_GPL(trace_array_get_by_name);
+
 /**
- * trace_array_get_by_name - Create/Lookup a trace array, given its name.
+ * trace_array_get_by_name_ext - Create/Lookup a trace array, given its name.
  * @name: The name of the trace array to be looked up/created.
  * @systems: A list of systems to create event directories for (NULL for all)
  *
@@ -9663,7 +9671,8 @@ out_unlock:
  * trace_array_put() is called, user space can not delete it.
  *
  */
-struct trace_array *trace_array_get_by_name(const char *name, const char *systems)
+struct trace_array *trace_array_get_by_name_ext(const char *name,
+						const char *systems)
 {
 	struct trace_array *tr;
 
@@ -9687,11 +9696,14 @@ out_unlock:
 	mutex_unlock(&event_mutex);
 	return tr;
 }
-EXPORT_SYMBOL_GPL(trace_array_get_by_name);
+EXPORT_SYMBOL_GPL(trace_array_get_by_name_ext);
 
 static int __remove_instance(struct trace_array *tr)
 {
 	int i;
+	struct trace_array_ext *tr_ext = container_of(tr,
+						      struct trace_array_ext,
+						      trace_array);
 
 	/* Reference counter for a newly created trace array = 1. */
 	if (tr->ref > 1 || (tr->current_trace && tr->trace_ref))
@@ -9722,9 +9734,9 @@ static int __remove_instance(struct trace_array *tr)
 
 	free_cpumask_var(tr->pipe_cpumask);
 	free_cpumask_var(tr->tracing_cpumask);
-	kfree_const(tr->system_names);
+	kfree_const(tr_ext->system_names);
 	kfree(tr->name);
-	kfree(tr);
+	kfree(tr_ext);
 
 	return 0;
 }
@@ -10527,7 +10539,7 @@ __init static void enable_instances(void)
 		if (IS_ENABLED(CONFIG_TRACER_MAX_TRACE))
 			do_allocate_snapshot(tok);
 
-		tr = trace_array_get_by_name(tok, NULL);
+		tr = trace_array_get_by_name(tok);
 		if (!tr) {
 			pr_warn("Failed to create instance buffer %s\n", curr_str);
 			continue;

kernel/trace/trace.h

@@ -377,7 +377,6 @@ struct trace_array {
 	unsigned char		trace_flags_index[TRACE_FLAGS_MAX_SIZE];
 	unsigned int		flags;
 	raw_spinlock_t		start_lock;
-	const char		*system_names;
 	struct list_head	err_log;
 	struct dentry		*dir;
 	struct dentry		*options;
@@ -413,6 +412,11 @@ struct trace_array {
 	struct trace_func_repeats	__percpu *last_func_repeats;
 };
 
+struct trace_array_ext {
+	const char		*system_names;
+	struct trace_array	trace_array;
+};
+
 enum {
 	TRACE_ARRAY_FL_GLOBAL	= (1 << 0)
 };

kernel/trace/trace_boot.c

@@ -633,7 +633,7 @@ trace_boot_init_instances(struct xbc_node *node)
 		if (!p || *p == '\0')
 			continue;
 
-		tr = trace_array_get_by_name(p, NULL);
+		tr = trace_array_get_by_name(p);
 		if (!tr) {
 			pr_err("Failed to get trace instance %s\n", p);
 			continue;

kernel/trace/trace_events.c

@@ -3070,8 +3070,11 @@ trace_create_new_event(struct trace_event_call *call,
 	struct trace_pid_list *pid_list;
 	struct trace_event_file *file;
 	unsigned int first;
+	struct trace_array_ext *tr_ext = container_of(tr,
+						      struct trace_array_ext,
+						      trace_array);
 
-	if (!event_in_systems(call, tr->system_names))
+	if (!event_in_systems(call, tr_ext->system_names))
 		return NULL;
 
 	file = kmem_cache_alloc(file_cachep, GFP_TRACE);

samples/ftrace/sample-trace-array.c

@@ -105,7 +105,8 @@ static int __init sample_trace_array_init(void)
 	 * NOTE: This function increments the reference counter
 	 * associated with the trace array - "tr".
 	 */
-	tr = trace_array_get_by_name("sample-instance", "sched,timer,kprobes");
+	tr = trace_array_get_by_name_ext("sample-instance",
+					 "sched,timer,kprobes");
 
 	if (!tr)
 		return -1;