dynamic_debug: add an option to enable dynamic debug for modules only

Instead of enabling dynamic debug globally with CONFIG_DYNAMIC_DEBUG,
CONFIG_DYNAMIC_DEBUG_CORE will only enable core function of dynamic
debug.  With the DYNAMIC_DEBUG_MODULE defined for any modules, dynamic
debug will be tied to them.

This is useful for people who only want to enable dynamic debug for
kernel modules without worrying about kernel image size and memory
consumption is increasing too much.

[[email protected]: v2]
  Link: http://lkml.kernel.org/r/[email protected]

Signed-off-by: Orson Zhai <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Acked-by: Petr Mladek <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Jason Baron <[email protected]>
Cc: Randy Dunlap <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 8f199f403ab5..321437bbf87d 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1032,8 +1032,13 @@ static int __init dynamic_debug_init(void)
 	int verbose_bytes = 0;
 
 	if (&__start___verbose == &__stop___verbose) {
-		pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
-		return 1;
+		if (IS_ENABLED(CONFIG_DYNAMIC_DEBUG)) {
+			pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
+			return 1;
+		}
+		pr_info("Ignore empty _ddebug table in a CONFIG_DYNAMIC_DEBUG_CORE build\n");
+		ddebug_init_success = 1;
+		return 0;
 	}
 	iter = __start___verbose;
 	modname = iter->modname;