ftrace: Allow subops filtering to be modified

The subops filters use a "manager" ops to enable and disable its filters.
The manager ops can handle more than one subops, and its filter is what
controls what functions get set. Add a ftrace_hash_move_and_update_subops()
function that will update the manager ops when the subops filters change.

Link: https://lore.kernel.org/linux-trace-kernel/20240603190822.673932251@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Guo Ren <guoren@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

include/linux/ftrace.h

@@ -227,6 +227,7 @@ ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops);
  *             ftrace_enabled.
  * DIRECT - Used by the direct ftrace_ops helper for direct functions
  *            (internal ftrace only, should not be used by others)
+ * SUBOP  - Is controlled by another op in field managed.
  */
 enum {
 	FTRACE_OPS_FL_ENABLED			= BIT(0),
@@ -247,6 +248,7 @@ enum {
 	FTRACE_OPS_FL_TRACE_ARRAY		= BIT(15),
 	FTRACE_OPS_FL_PERMANENT                 = BIT(16),
 	FTRACE_OPS_FL_DIRECT			= BIT(17),
+	FTRACE_OPS_FL_SUBOP			= BIT(18),
 };
 
 #ifndef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
@@ -336,6 +338,7 @@ struct ftrace_ops {
 	struct list_head		list;
 	struct list_head		subop_list;
 	ftrace_ops_func_t		ops_func;
+	struct ftrace_ops		*managed;
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 	unsigned long			direct_call;
 #endif

kernel/trace/ftrace.c

@@ -3343,10 +3343,28 @@ static bool ops_equal(struct ftrace_hash *A, struct ftrace_hash *B)
 	return true;
 }
 
-static int ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
-					   struct ftrace_hash **orig_hash,
-					   struct ftrace_hash *hash,
-					   int enable);
+static void ftrace_ops_update_code(struct ftrace_ops *ops,
+				   struct ftrace_ops_hash *old_hash);
+
+static int __ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
+					     struct ftrace_hash **orig_hash,
+					     struct ftrace_hash *hash,
+					     int enable)
+{
+	struct ftrace_ops_hash old_hash_ops;
+	struct ftrace_hash *old_hash;
+	int ret;
+
+	old_hash = *orig_hash;
+	old_hash_ops.filter_hash = ops->func_hash->filter_hash;
+	old_hash_ops.notrace_hash = ops->func_hash->notrace_hash;
+	ret = ftrace_hash_move(ops, enable, orig_hash, hash);
+	if (!ret) {
+		ftrace_ops_update_code(ops, &old_hash_ops);
+		free_ftrace_hash_rcu(old_hash);
+	}
+	return ret;
+}
 
 static int ftrace_update_ops(struct ftrace_ops *ops, struct ftrace_hash *filter_hash,
 			     struct ftrace_hash *notrace_hash)
@@ -3354,15 +3372,15 @@ static int ftrace_update_ops(struct ftrace_ops *ops, struct ftrace_hash *filter_
 	int ret;
 
 	if (!ops_equal(filter_hash, ops->func_hash->filter_hash)) {
-		ret = ftrace_hash_move_and_update_ops(ops, &ops->func_hash->filter_hash,
-						      filter_hash, 1);
+		ret = __ftrace_hash_move_and_update_ops(ops, &ops->func_hash->filter_hash,
+							filter_hash, 1);
 		if (ret < 0)
 			return ret;
 	}
 
 	if (!ops_equal(notrace_hash, ops->func_hash->notrace_hash)) {
-		ret = ftrace_hash_move_and_update_ops(ops, &ops->func_hash->notrace_hash,
-						      notrace_hash, 0);
+		ret = __ftrace_hash_move_and_update_ops(ops, &ops->func_hash->notrace_hash,
+							notrace_hash, 0);
 		if (ret < 0)
 			return ret;
 	}
@@ -3435,7 +3453,8 @@ int ftrace_startup_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, int
 		} else {
 			free_ftrace_hash(save_filter_hash);
 			free_ftrace_hash(save_notrace_hash);
-			subops->flags |= FTRACE_OPS_FL_ENABLED;
+			subops->flags |= FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_SUBOP;
+			subops->managed = ops;
 		}
 		return ret;
 	}
@@ -3489,11 +3508,12 @@ int ftrace_startup_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, int
 	ret = ftrace_update_ops(ops, filter_hash, notrace_hash);
 	free_ftrace_hash(filter_hash);
 	free_ftrace_hash(notrace_hash);
-	if (ret < 0)
+	if (ret < 0) {
 		list_del(&subops->list);
-	else
-		subops->flags |= FTRACE_OPS_FL_ENABLED;
-
+	} else {
+		subops->flags |= FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_SUBOP;
+		subops->managed = ops;
+	}
 	return ret;
 }
 
@@ -3538,6 +3558,8 @@ int ftrace_shutdown_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, in
 		free_ftrace_hash(ops->func_hash->notrace_hash);
 		ops->func_hash->filter_hash = EMPTY_HASH;
 		ops->func_hash->notrace_hash = EMPTY_HASH;
+		subops->flags &= ~(FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_SUBOP);
+		subops->managed = NULL;
 
 		return 0;
 	}
@@ -3553,16 +3575,65 @@ int ftrace_shutdown_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, in
 	}
 
 	ret = ftrace_update_ops(ops, filter_hash, notrace_hash);
-	if (ret < 0)
+	if (ret < 0) {
 		list_add(&subops->list, &ops->subop_list);
-	else
-		subops->flags &= ~FTRACE_OPS_FL_ENABLED;
-
+	} else {
+		subops->flags &= ~(FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_SUBOP);
+		subops->managed = NULL;
+	}
 	free_ftrace_hash(filter_hash);
 	free_ftrace_hash(notrace_hash);
 	return ret;
 }
 
+static int ftrace_hash_move_and_update_subops(struct ftrace_ops *subops,
+					      struct ftrace_hash **orig_subhash,
+					      struct ftrace_hash *hash,
+					      int enable)
+{
+	struct ftrace_ops *ops = subops->managed;
+	struct ftrace_hash **orig_hash;
+	struct ftrace_hash *save_hash;
+	struct ftrace_hash *new_hash;
+	int ret;
+
+	/* Manager ops can not be subops (yet) */
+	if (WARN_ON_ONCE(!ops || ops->flags & FTRACE_OPS_FL_SUBOP))
+		return -EINVAL;
+
+	/* Move the new hash over to the subops hash */
+	save_hash = *orig_subhash;
+	*orig_subhash = __ftrace_hash_move(hash);
+	if (!*orig_subhash) {
+		*orig_subhash = save_hash;
+		return -ENOMEM;
+	}
+
+	/* Create a new_hash to hold the ops new functions */
+	if (enable) {
+		orig_hash = &ops->func_hash->filter_hash;
+		new_hash = append_hashes(ops);
+	} else {
+		orig_hash = &ops->func_hash->notrace_hash;
+		new_hash = intersect_hashes(ops);
+	}
+
+	/* Move the hash over to the new hash */
+	ret = __ftrace_hash_move_and_update_ops(ops, orig_hash, new_hash, enable);
+
+	free_ftrace_hash(new_hash);
+
+	if (ret) {
+		/* Put back the original hash */
+		free_ftrace_hash_rcu(*orig_subhash);
+		*orig_subhash = save_hash;
+	} else {
+		free_ftrace_hash_rcu(save_hash);
+	}
+	return ret;
+}
+
+
 static u64		ftrace_update_time;
 unsigned long		ftrace_update_tot_cnt;
 unsigned long		ftrace_number_of_pages;
@@ -4779,19 +4850,33 @@ static int ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
 					   struct ftrace_hash *hash,
 					   int enable)
 {
-	struct ftrace_ops_hash old_hash_ops;
-	struct ftrace_hash *old_hash;
-	int ret;
+	if (ops->flags & FTRACE_OPS_FL_SUBOP)
+		return ftrace_hash_move_and_update_subops(ops, orig_hash, hash, enable);
 
-	old_hash = *orig_hash;
-	old_hash_ops.filter_hash = ops->func_hash->filter_hash;
-	old_hash_ops.notrace_hash = ops->func_hash->notrace_hash;
-	ret = ftrace_hash_move(ops, enable, orig_hash, hash);
-	if (!ret) {
-		ftrace_ops_update_code(ops, &old_hash_ops);
-		free_ftrace_hash_rcu(old_hash);
+	/*
+	 * If this ops is not enabled, it could be sharing its filters
+	 * with a subop. If that's the case, update the subop instead of
+	 * this ops. Shared filters are only allowed to have one ops set
+	 * at a time, and if we update the ops that is not enabled,
+	 * it will not affect subops that share it.
+	 */
+	if (!(ops->flags & FTRACE_OPS_FL_ENABLED)) {
+		struct ftrace_ops *op;
+
+		/* Check if any other manager subops maps to this hash */
+		do_for_each_ftrace_op(op, ftrace_ops_list) {
+			struct ftrace_ops *subops;
+
+			list_for_each_entry(subops, &op->subop_list, list) {
+				if ((subops->flags & FTRACE_OPS_FL_ENABLED) &&
+				     subops->func_hash == ops->func_hash) {
+					return ftrace_hash_move_and_update_subops(subops, orig_hash, hash, enable);
+				}
+			}
+		} while_for_each_ftrace_op(op);
 	}
-	return ret;
+
+	return __ftrace_hash_move_and_update_ops(ops, orig_hash, hash, enable);
 }
 
 static bool module_exists(const char *module)