From 5ca173974888368fecfb17ae6fe455df5fd2a9d2 Mon Sep 17 00:00:00 2001
From: Andrew Halaney <ahalaney@redhat.com>
Date: Wed, 13 Oct 2021 11:40:20 -0400
Subject: [PATCH] dyndbg: make dyndbg a known cli param
Git-commit: 5ca173974888368fecfb17ae6fe455df5fd2a9d2
Patch-mainline: v5.16-rc1
References: git-fixes stable-5.14.19

Right now dyndbg shows up as an unknown parameter if used on boot:

    Unknown command line parameters: dyndbg=+p

That's because it is unknown, it doesn't sit in the __param
section, so the processing done to warn users supplying an unknown
parameter doesn't think it is legitimate.

Install a dummy handler to register it. dynamic debug needs to search
the whole command line for modules listed that are currently builtin,
so there's no real work to be done in this callback.

Fixes: 86d1919a4fb0 ("init: print out unknown kernel parameters")
Tested-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Link: https://lore.kernel.org/r/1634139622-20667-2-git-send-email-jbaron@akamai.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 lib/dynamic_debug.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index dfe1e6a857bc..cd222a1c1238 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -761,6 +761,18 @@ static __init int ddebug_setup_query(char *str)
 
 __setup("ddebug_query=", ddebug_setup_query);
 
+/*
+ * Install a noop handler to make dyndbg look like a normal kernel cli param.
+ * This avoids warnings about dyndbg being an unknown cli param when supplied
+ * by a user.
+ */
+static __init int dyndbg_setup(char *str)
+{
+	return 1;
+}
+
+__setup("dyndbg=", dyndbg_setup);
+
 /*
  * File_ops->write method for <debugfs>/dynamic_debug/control.  Gathers the
  * command text from userspace, parses and executes it.
-- 
2.26.2