[PATCH RFC] livepatch: add sysfs entry "patched" for each klp_object

[Song Liu <song@kernel.org>]

I was debugging an issue that a livepatch appears to be attached, but
actually not. It turns out that there is a mismatch in module name
(abc-xyz vs. abc_xyz), klp_find_object_module failed to find the module.

Add per klp_object sysfs entry "patched" to make it easier to debug such
issues.

Signed-off-by: Song Liu <song@kernel.org>
---
 kernel/livepatch/core.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 5c0d8a4eba13..a9e20c561fef 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -364,6 +364,7 @@ static void klp_clear_object_relocations(struct module *pmod,
  * /sys/kernel/livepatch/<patch>/transition
  * /sys/kernel/livepatch/<patch>/force
  * /sys/kernel/livepatch/<patch>/<object>
+ * /sys/kernel/livepatch/<patch>/<object>/patched
  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
  */
 static int __klp_disable_patch(struct klp_patch *patch);
@@ -470,6 +471,22 @@ static struct attribute *klp_patch_attrs[] = {
 };
 ATTRIBUTE_GROUPS(klp_patch);
 
+static ssize_t patched_show(struct kobject *kobj,
+			    struct kobj_attribute *attr, char *buf)
+{
+	struct klp_object *obj;
+
+	obj = container_of(kobj, struct klp_object, kobj);
+	return snprintf(buf, PAGE_SIZE, "%d\n", obj->patched);
+}
+
+static struct kobj_attribute patched_kobj_attr = __ATTR_RO(patched);
+static struct attribute *klp_object_attrs[] = {
+	&patched_kobj_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(klp_object);
+
 static void klp_free_object_dynamic(struct klp_object *obj)
 {
 	kfree(obj->name);
@@ -615,6 +632,7 @@ static void klp_kobj_release_object(struct kobject *kobj)
 static struct kobj_type klp_ktype_object = {
 	.release = klp_kobj_release_object,
 	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = klp_object_groups,
 };
 
 static void klp_kobj_release_func(struct kobject *kobj)
-- 
2.30.2