dyndbg: use the module notifier callbacks

Bring dynamic debug in line with other subsystems by using the module
notifier callbacks. This results in a net decrease in core module
code.

Additionally, Jim Cromie has a new dynamic debug classmap feature,
which requires that jump labels be initialized prior to dynamic debug.
Specifically, the new feature toggles a jump label from the existing
dynamic_debug_setup() function. However, this does not currently work
properly, because jump labels are initialized via the
'module_notify_list' notifier chain, which is invoked after the
current call to dynamic_debug_setup(). Thus, this patch ensures that
jump labels are initialized prior to dynamic debug by setting the
dynamic debug notifier priority to 0, while jump labels have the
higher priority of 1.

Tested by Jim using his new test case, and I've verfied the correct
printing via: # modprobe test_dynamic_debug dyndbg.

Link: https://lore.kernel.org/lkml/20230113193016.749791-21-jim.cromie@gmail.com/
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202302190427.9iIK2NfJ-lkp@intel.com/
Tested-by: Jim Cromie <jim.cromie@gmail.com>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
CC: Jim Cromie <jim.cromie@gmail.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

2 files changed, 8 insertions, 24 deletions

diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index c6c44ceca07a..e3883b7d4840 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -45,7 +45,6 @@ extern const struct kernel_symbol __stop___ksymtab_gpl[];
 extern const s32 __start___kcrctab[];
 extern const s32 __start___kcrctab_gpl[];
 
-#include <linux/dynamic_debug.h>
 struct load_info {
 	const char *name;
 	/* pointer to module in temporary copy, freed at end of load_module() */
@@ -55,7 +54,6 @@ struct load_info {
 	Elf_Shdr *sechdrs;
 	char *secstrings, *strtab;
 	unsigned long symoffs, stroffs, init_typeoffs, core_typeoffs;
-	struct _ddebug_info dyndbg;
 	bool sig_ok;
 #ifdef CONFIG_KALLSYMS
 	unsigned long mod_kallsyms_init_off;
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 1fa529668a45..b4759f1695b7 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1216,9 +1216,6 @@ static void free_module(struct module *mod)
 	mod->state = MODULE_STATE_UNFORMED;
 	mutex_unlock(&module_mutex);
 
-	/* Remove dynamic debug info */
-	ddebug_remove_module(mod->name);
-
 	/* Arch-specific cleanup. */
 	module_arch_cleanup(mod);
 
@@ -1619,19 +1616,6 @@ static void free_modinfo(struct module *mod)
 	}
 }
 
-static void dynamic_debug_setup(struct module *mod, struct _ddebug_info *dyndbg)
-{
-	if (!dyndbg->num_descs)
-		return;
-	ddebug_add_module(dyndbg, mod->name);
-}
-
-static void dynamic_debug_remove(struct module *mod, struct _ddebug_info *dyndbg)
-{
-	if (dyndbg->num_descs)
-		ddebug_remove_module(mod->name);
-}
-
 void * __weak module_alloc(unsigned long size)
 {
 	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
@@ -2137,10 +2121,14 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 	if (section_addr(info, "__obsparm"))
 		pr_warn("%s: Ignoring obsolete parameters\n", mod->name);
 
-	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);
+#ifdef CONFIG_DYNAMIC_DEBUG_CORE
+	mod->dyndbg_info.descs = section_objs(info, "__dyndbg",
+					      sizeof(*mod->dyndbg_info.descs),
+					      &mod->dyndbg_info.num_descs);
+	mod->dyndbg_info.classes = section_objs(info, "__dyndbg_classes",
+						sizeof(*mod->dyndbg_info.classes),
+						&mod->dyndbg_info.num_classes);
+#endif
 
 	return 0;
 }
@@ -2824,7 +2812,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	}
 
 	init_build_id(mod, info);
-	dynamic_debug_setup(mod, &info->dyndbg);
 
 	/* Ftrace init must be called in the MODULE_STATE_UNFORMED state */
 	ftrace_module_init(mod);
@@ -2888,7 +2875,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
 
  ddebug_cleanup:
 	ftrace_release_mod(mod);
-	dynamic_debug_remove(mod, &info->dyndbg);
 	synchronize_rcu();
 	kfree(mod->args);
  free_arch_cleanup: