kernel/module: add __dyndbg_classes section

Add __dyndbg_classes section, using __dyndbg as a model. Use it:

vmlinux.lds.h:

KEEP the new section, which also silences orphan section warning on
loadable modules.  Add (__start_/__stop_)__dyndbg_classes linker
symbols for the c externs (below).

kernel/module/main.c:
- fill new fields in find_module_sections(), using section_objs()
- extend callchain prototypes
  to pass classes, length
  load_module(): pass new info to dynamic_debug_setup()
  dynamic_debug_setup(): new params, pass through to ddebug_add_module()

dynamic_debug.c:
- add externs to the linker symbols.

ddebug_add_module():
- It currently builds a debug_table, and *will* find and attach classes.

dynamic_debug_init():
- add class fields to the _ddebug_info cursor var: di.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-16-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 14 insertions, 0 deletions

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 7515a465ec03..9b8bd5504ad9 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -345,6 +345,9 @@
 	*(__tracepoints)						\
 	/* implement dynamic printk debug */				\
 	. = ALIGN(8);							\
+	__start___dyndbg_classes = .;					\
+	KEEP(*(__dyndbg_classes))					\
+	__stop___dyndbg_classes = .;					\
 	__start___dyndbg = .;						\
 	KEEP(*(__dyndbg))						\
 	__stop___dyndbg = .;						\
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 98dbf1d49984..9073a43a2039 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -114,7 +114,9 @@ struct ddebug_class_map {
 /* encapsulate linker provided built-in (or module) dyndbg data */
 struct _ddebug_info {
 	struct _ddebug *descs;
+	struct ddebug_class_map *classes;
 	unsigned int num_descs;
+	unsigned int num_classes;
 };
 
 #if defined(CONFIG_DYNAMIC_DEBUG_CORE)
diff --git a/kernel/module/main.c b/kernel/module/main.c
index a26b436ad992..00641d1022a5 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2113,6 +2113,8 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 
 	info->dyndbg.descs = section_objs(info, "__dyndbg",
 					sizeof(*info->dyndbg.descs), &info->dyndbg.num_descs);
+	info->dyndbg.classes = section_objs(info, "__dyndbg_classes",
+					sizeof(*info->dyndbg.classes), &info->dyndbg.num_classes);
 
 	return 0;
 }
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index c358ccdf4a39..fb31a1a2fc3f 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -41,6 +41,8 @@
 
 extern struct _ddebug __start___dyndbg[];
 extern struct _ddebug __stop___dyndbg[];
+extern struct ddebug_class_map __start___dyndbg_classes[];
+extern struct ddebug_class_map __stop___dyndbg_classes[];
 
 struct ddebug_table {
 	struct list_head link;
@@ -1079,7 +1081,9 @@ static int __init dynamic_debug_init(void)
 
 	struct _ddebug_info di = {
 		.descs = __start___dyndbg,
+		.classes = __start___dyndbg_classes,
 		.num_descs = __stop___dyndbg - __start___dyndbg,
+		.num_classes = __stop___dyndbg_classes - __start___dyndbg_classes,
 	};
 
 	if (&__start___dyndbg == &__stop___dyndbg) {
@@ -1122,6 +1126,9 @@ static int __init dynamic_debug_init(void)
 		 i, mod_ct, (int)((mod_ct * sizeof(struct ddebug_table)) >> 10),
 		 (int)((i * sizeof(struct _ddebug)) >> 10));
 
+	if (di.num_classes)
+		v2pr_info("  %d builtin ddebug class-maps\n", di.num_classes);
+
 	/* now that ddebug tables are loaded, process all boot args
 	 * again to find and activate queries given in dyndbg params.
 	 * While this has already been done for known boot params, it