From 47a9749d381f02868b4f4bbe1bc841f3f38ac1a1 Mon Sep 17 00:00:00 2001
From: Zhipeng Xie <xiezhipeng1@huawei.com>
Date: Sun, 22 Nov 2020 21:40:39 +0800
Subject: [PATCH 19/24] Fix relocation not resolved when new functions exported
 only

When no functions changed and new functions exported, kobject is not
created, so livepatch will not call klp_init_object and relocation
in new functions are not resolved.

Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
---
 kmod/patch/kpatch-patch.h         |  4 ++++
 kmod/patch/kpatch.lds.S           |  6 ++++++
 kmod/patch/livepatch-patch-hook.c | 19 +++++++++++++++++++
 kpatch-build/create-diff-object.c | 26 ++++++++++++++++++++++++++
 4 files changed, 55 insertions(+)

diff --git a/kmod/patch/kpatch-patch.h b/kmod/patch/kpatch-patch.h
index 6e39364..33f2056 100644
--- a/kmod/patch/kpatch-patch.h
+++ b/kmod/patch/kpatch-patch.h
@@ -63,6 +63,10 @@ struct kpatch_post_unpatch_callback {
 	void (*callback)(void *obj);
 	char *objname;
 };
+struct kpatch_object {
+	char *objname;
+};
 
 extern unsigned long __kpatch_force_funcs[], __kpatch_force_funcs_end[];
+extern struct kpatch_object __kpatch_objects[], __kpatch_objects_end[];
 #endif /* _KPATCH_PATCH_H_ */
diff --git a/kmod/patch/kpatch.lds.S b/kmod/patch/kpatch.lds.S
index bc5de82..4c4d77b 100644
--- a/kmod/patch/kpatch.lds.S
+++ b/kmod/patch/kpatch.lds.S
@@ -47,4 +47,10 @@ SECTIONS
     __kpatch_force_funcs_end = . ;
     QUAD(0);
   }
+  .kpatch.objects : {
+    __kpatch_objects = . ;
+    *(.kpatch.objects)
+    __kpatch_objects_end = . ;
+    QUAD(0);
+  }
 }
diff --git a/kmod/patch/livepatch-patch-hook.c b/kmod/patch/livepatch-patch-hook.c
index 71439d9..9e56fe3 100644
--- a/kmod/patch/livepatch-patch-hook.c
+++ b/kmod/patch/livepatch-patch-hook.c
@@ -442,6 +442,22 @@ static int patch_is_func_forced(unsigned long addr)
 	return 0;
 }
 
+static int add_kpatch_objects(void)
+{
+	struct kpatch_object *p_kpatch_object;
+	struct patch_object *object;
+
+	for (p_kpatch_object = __kpatch_objects;
+	     p_kpatch_object < __kpatch_objects_end;
+	     p_kpatch_object++) {
+		object = patch_find_object_by_name(p_kpatch_object->objname);
+		if (!object)
+			return -ENOMEM;
+	}
+
+	return 0;
+}
+
 static int __init patch_init(void)
 {
 	struct kpatch_patch_func *kfunc;
@@ -485,6 +501,9 @@ static int __init patch_init(void)
 	if (ret)
 		goto out;
 
+	ret = add_kpatch_objects();
+	if (ret)
+		goto out;
 	/* past this point, only possible return code is -ENOMEM */
 	ret = -ENOMEM;
 
diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index 6b915ae..0bef022 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -2916,6 +2916,27 @@ static void kpatch_create_kpatch_arch_section(struct kpatch_elf *kelf, char *obj
 	karch_sec->sh.sh_size = karch_sec->data->d_size;
 }
 
+static void kpatch_create_kpatch_object_section(struct kpatch_elf *kelf, char *objname)
+{
+	struct symbol *strsym;
+	struct rela *rela;
+	struct section *kobj_sec;
+
+	kobj_sec = create_section_pair(kelf, ".kpatch.objects", sizeof(struct kpatch_object), 1);
+
+	/* lookup strings symbol */
+	strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings");
+	if (!strsym)
+		ERROR("can't find .kpatch.strings symbol");
+
+	/* entries[index].objname */
+	ALLOC_LINK(rela, &kobj_sec->rela->relas);
+	rela->sym = strsym;
+	rela->type = ABSOLUTE_RELA_TYPE;
+	rela->addend = offset_of_string(&kelf->strings, objname);
+	rela->offset = (unsigned int)(offsetof(struct kpatch_object, objname));
+}
+
 static void kpatch_process_special_sections(struct kpatch_elf *kelf,
 					    struct lookup_table *lookup)
 {
@@ -3973,6 +3994,11 @@ int main(int argc, char *argv[])
 	kpatch_create_intermediate_sections(kelf_out, lookup, parent_name, patch_name);
 	kpatch_create_kpatch_arch_section(kelf_out, parent_name);
 	kpatch_create_callbacks_objname_rela(kelf_out, parent_name);
+
+	if (!num_changed && new_globals_exist) {
+		kpatch_create_kpatch_object_section(kelf_out, parent_name);
+	}
+
 	kpatch_build_strings_section_data(kelf_out);
 
 	kpatch_create_mcount_sections(kelf_out);
-- 
2.23.0