linux-kernel - [tip: objtool/core] livepatch/klp-build: Add stub init code for livepatch modules

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Message-ID: <176060832614.709179.8750464085170794957.tip-bot2@tip-bot2>
Date: Thu, 16 Oct 2025 09:52:06 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Petr Mladek <pmladek@...e.com>, Joe Lawrence <joe.lawrence@...hat.com>,
 Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: objtool/core] livepatch/klp-build: Add stub init code for
 livepatch modules

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     59adee07b568fb78e2bf07df1f22f3fe45b7240a
Gitweb:        https://git.kernel.org/tip/59adee07b568fb78e2bf07df1f22f3fe45b7240a
Author:        Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate:    Wed, 17 Sep 2025 09:04:07 -07:00
Committer:     Josh Poimboeuf <jpoimboe@...nel.org>
CommitterDate: Tue, 14 Oct 2025 14:50:19 -07:00

livepatch/klp-build: Add stub init code for livepatch modules

Add a module initialization stub which can be linked with binary diff
objects to produce a livepatch module.

Acked-by: Petr Mladek <pmladek@...e.com>
Tested-by: Joe Lawrence <joe.lawrence@...hat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 scripts/livepatch/init.c | 108 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 108 insertions(+)
 create mode 100644 scripts/livepatch/init.c

diff --git a/scripts/livepatch/init.c b/scripts/livepatch/init.c
new file mode 100644
index 0000000..2274d8f
--- /dev/null
+++ b/scripts/livepatch/init.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Init code for a livepatch kernel module
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/livepatch.h>
+
+extern struct klp_object_ext __start_klp_objects[];
+extern struct klp_object_ext __stop_klp_objects[];
+
+static struct klp_patch *patch;
+
+static int __init livepatch_mod_init(void)
+{
+	struct klp_object *objs;
+	unsigned int nr_objs;
+	int ret;
+
+	nr_objs = __stop_klp_objects - __start_klp_objects;
+
+	if (!nr_objs) {
+		pr_err("nothing to patch!\n");
+		ret = -EINVAL;
+		goto err;
+	}
+
+	patch = kzalloc(sizeof(*patch), GFP_KERNEL);
+	if (!patch) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	objs = kzalloc(sizeof(struct klp_object) * (nr_objs + 1),  GFP_KERNEL);
+	if (!objs) {
+		ret = -ENOMEM;
+		goto err_free_patch;
+	}
+
+	for (int i = 0; i < nr_objs; i++) {
+		struct klp_object_ext *obj_ext = __start_klp_objects + i;
+		struct klp_func_ext *funcs_ext = obj_ext->funcs;
+		unsigned int nr_funcs = obj_ext->nr_funcs;
+		struct klp_func *funcs = objs[i].funcs;
+		struct klp_object *obj = objs + i;
+
+		funcs = kzalloc(sizeof(struct klp_func) * (nr_funcs + 1), GFP_KERNEL);
+		if (!funcs) {
+			ret = -ENOMEM;
+			for (int j = 0; j < i; j++)
+				kfree(objs[i].funcs);
+			goto err_free_objs;
+		}
+
+		for (int j = 0; j < nr_funcs; j++) {
+			funcs[j].old_name   = funcs_ext[j].old_name;
+			funcs[j].new_func   = funcs_ext[j].new_func;
+			funcs[j].old_sympos = funcs_ext[j].sympos;
+		}
+
+		obj->name = obj_ext->name;
+		obj->funcs = funcs;
+
+		memcpy(&obj->callbacks, &obj_ext->callbacks, sizeof(struct klp_callbacks));
+	}
+
+	patch->mod = THIS_MODULE;
+	patch->objs = objs;
+
+	/* TODO patch->states */
+
+#ifdef KLP_NO_REPLACE
+	patch->replace = false;
+#else
+	patch->replace = true;
+#endif
+
+	return klp_enable_patch(patch);
+
+err_free_objs:
+	kfree(objs);
+err_free_patch:
+	kfree(patch);
+err:
+	return ret;
+}
+
+static void __exit livepatch_mod_exit(void)
+{
+	unsigned int nr_objs;
+
+	nr_objs = __stop_klp_objects - __start_klp_objects;
+
+	for (int i = 0; i < nr_objs; i++)
+		kfree(patch->objs[i].funcs);
+
+	kfree(patch->objs);
+	kfree(patch);
+}
+
+module_init(livepatch_mod_init);
+module_exit(livepatch_mod_exit);
+MODULE_LICENSE("GPL");
+MODULE_INFO(livepatch, "Y");
+MODULE_DESCRIPTION("Livepatch module");