ftrace: Use hash argument for tmp_ops in update_ftrace_direct_mod

The modify logic registers temporary ftrace_ops object (tmp_ops) to trigger
the slow path for all direct callers to be able to safely modify attached
addresses.

At the moment we use ops->func_hash for tmp_ops filter, which represents all
the systems attachments. It's faster to use just the passed hash filter, which
contains only the modified sites and is always a subset of the ops->func_hash.

Cc: Alexei Starovoitov <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Menglong Dong <[email protected]>
Cc: Song Liu <[email protected]>
Link: https://patch.msgid.link/[email protected]
Fixes: e93672f ("ftrace: Add update_ftrace_direct_mod function")
Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: olsajiri

kernel/trace/ftrace.c

@@ -6606,9 +6606,9 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
 	if (!orig_hash)
 		goto unlock;
 
-	/* Enable the tmp_ops to have the same functions as the direct ops */
+	/* Enable the tmp_ops to have the same functions as the hash object. */
 	ftrace_ops_init(&tmp_ops);
-	tmp_ops.func_hash = ops->func_hash;
+	tmp_ops.func_hash->filter_hash = hash;
 
 	err = register_ftrace_function_nolock(&tmp_ops);
 	if (err)