linux-kernel - [v2 2/3] kernel: refactor and globalize lookup_or_create_module

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Message-Id: <20250207054538.1110340-3-shyamsaini@linux.microsoft.com>
Date: Thu,  6 Feb 2025 21:45:37 -0800
From: Shyam Saini <shyamsaini@...ux.microsoft.com>
To: linux-kernel@...r.kernel.org,
	linux-modules@...r.kernel.org
Cc: code@...icks.com,
	linux@...musvillemoes.dk,
	christophe.leroy@...roup.eu,
	hch@...radead.org,
	mcgrof@...nel.org,
	frkaya@...ux.microsoft.com,
	vijayb@...ux.microsoft.com,
	petr.pavlu@...e.com,
	linux@...ssschuh.net,
	samitolvanen@...gle.com,
	da.gomez@...sung.com,
	gregkh@...uxfoundation.org,
	rafael@...nel.org,
	dakr@...nel.org
Subject: [v2 2/3] kernel: refactor and globalize lookup_or_create_module_kobject()

lookup_or_create_module_kobject() is static and marked as __init,
this is not ideal for global usage.

Fix this limitation by refactoring and declaring this as global:
 - Refactor it by removing BUG_ON() and 'if else' construct by returning
   early
 - Remove static and __init markers from the function and add its
   declaration in module.h
 - Mark this function as "__modinit". To facilitate this, move the
   __modinit macro construct to module.h

Suggested-by: Rasmus Villemoes <linux@...musvillemoes.dk>
Signed-off-by: Shyam Saini <shyamsaini@...ux.microsoft.com>
---
 include/linux/module.h |  8 +++++++
 kernel/params.c        | 48 ++++++++++++++++++------------------------
 2 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index 12f8a7d4fc1c..57d09b4e4385 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -162,6 +162,14 @@ extern void cleanup_module(void);
 #define __INITRODATA_OR_MODULE __INITRODATA
 #endif /*CONFIG_MODULES*/
 
+#ifdef CONFIG_MODULES
+#define __modinit
+#else
+#define __modinit __init
+#endif
+
+struct module_kobject __modinit * lookup_or_create_module_kobject(const char *name);
+
 /* Generic info of form tag = "info" */
 #define MODULE_INFO(tag, info) __MODULE_INFO(tag, tag, info)
 
diff --git a/kernel/params.c b/kernel/params.c
index 4b43baaf7c83..5d16696b1daa 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -595,12 +595,6 @@ static ssize_t param_attr_store(const struct module_attribute *mattr,
 }
 #endif
 
-#ifdef CONFIG_MODULES
-#define __modinit
-#else
-#define __modinit __init
-#endif
-
 #ifdef CONFIG_SYSFS
 void kernel_param_lock(struct module *mod)
 {
@@ -763,38 +757,38 @@ void destroy_params(const struct kernel_param *params, unsigned num)
 			params[i].ops->free(params[i].arg);
 }
 
-static struct module_kobject * __init lookup_or_create_module_kobject(const char *name)
+struct module_kobject __modinit * lookup_or_create_module_kobject(const char *name)
 {
 	struct module_kobject *mk;
 	struct kobject *kobj;
 	int err;
 
 	kobj = kset_find_obj(module_kset, name);
-	if (kobj) {
-		mk = to_module_kobject(kobj);
-	} else {
-		mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
-		BUG_ON(!mk);
-
-		mk->mod = THIS_MODULE;
-		mk->kobj.kset = module_kset;
-		err = kobject_init_and_add(&mk->kobj, &module_ktype, NULL,
+	if (kobj)
+		return to_module_kobject(kobj);
+
+	mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
+	if (!mk)
+		return NULL;
+
+	mk->mod = THIS_MODULE;
+	mk->kobj.kset = module_kset;
+	err = kobject_init_and_add(&mk->kobj, &module_ktype, NULL,
 					   "%s", name);
 #ifdef CONFIG_MODULES
-		if (!err)
-			err = sysfs_create_file(&mk->kobj, &module_uevent.attr);
+	if (!err)
+		err = sysfs_create_file(&mk->kobj, &module_uevent.attr);
 #endif
-		if (err) {
-			kobject_put(&mk->kobj);
-			pr_crit("Adding module '%s' to sysfs failed (%d), the system may be unstable.\n",
-				name, err);
-			return NULL;
-		}
-
-		/* So that we hold reference in both cases. */
-		kobject_get(&mk->kobj);
+	if (err) {
+		kobject_put(&mk->kobj);
+		pr_crit("Adding module '%s' to sysfs failed (%d), the system may be unstable.\n",
+			name, err);
+		return NULL;
 	}
 
+	/* So that we hold reference in both cases. */
+	kobject_get(&mk->kobj);
+
 	return mk;
 }
 
-- 
2.34.1