linux-kernel - [PATCH v4 1/3] livepatch: use lists to manage patches, objects and functions

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Date:   Thu, 12 Oct 2017 17:12:27 -0400
From:   Jason Baron <jbaron@...mai.com>
To:     linux-kernel@...r.kernel.org, live-patching@...r.kernel.org
Cc:     jpoimboe@...hat.com, jeyu@...nel.org, jikos@...nel.org,
        mbenes@...e.cz, pmladek@...e.com
Subject: [PATCH v4 1/3] livepatch: use lists to manage patches, objects and functions

Currently klp_patch contains a pointer to a statically allocated array of
struct klp_object and struct klp_objects contains a pointer to a statically
allocated array of klp_func. In order to allow for the dynamic allocation
of objects and functions, link klp_patch, klp_object, and klp_func together
via linked lists. This allows us to more easily allocate new objects and
functions, while having the iterator be a simple linked list walk.

This patch is intended to be a no-op until atomic replace is introduced by
a subsequent patch.

Signed-off-by: Jason Baron <jbaron@...mai.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Jessica Yu <jeyu@...nel.org>
Cc: Jiri Kosina <jikos@...nel.org>
Cc: Miroslav Benes <mbenes@...e.cz>
Cc: Petr Mladek <pmladek@...e.com>
---
 include/linux/livepatch.h | 19 +++++++++++++++++--
 kernel/livepatch/core.c   |  8 ++++++--
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 194991e..482f90b 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -24,6 +24,7 @@
 #include <linux/module.h>
 #include <linux/ftrace.h>
 #include <linux/completion.h>
+#include <linux/list.h>
 
 #if IS_ENABLED(CONFIG_LIVEPATCH)
 
@@ -44,6 +45,7 @@
  * @old_addr:	the address of the function being patched
  * @kobj:	kobject for sysfs resources
  * @stack_node:	list node for klp_ops func_stack list
+ * @func_entry:	links struct klp_func to struct klp_object
  * @old_size:	size of the old function
  * @new_size:	size of the new function
  * @patched:	the func has been added to the klp_ops list
@@ -82,6 +84,7 @@ struct klp_func {
 	unsigned long old_addr;
 	struct kobject kobj;
 	struct list_head stack_node;
+	struct list_head func_entry;
 	unsigned long old_size, new_size;
 	bool patched;
 	bool transition;
@@ -94,6 +97,8 @@ struct klp_func {
  * @kobj:	kobject for sysfs resources
  * @mod:	kernel module associated with the patched object
  *		(NULL for vmlinux)
+ * @func_list:	head of list for struct klp_func
+ * @obj_entry:	links struct klp_object to struct klp_patch
  * @patched:	the object's funcs have been added to the klp_ops list
  */
 struct klp_object {
@@ -103,6 +108,8 @@ struct klp_object {
 
 	/* internal */
 	struct kobject kobj;
+	struct list_head func_list;
+	struct list_head obj_entry;
 	struct module *mod;
 	bool patched;
 };
@@ -114,6 +121,7 @@ struct klp_object {
  * @immediate:  patch all funcs immediately, bypassing safety mechanisms
  * @list:	list node for global list of registered patches
  * @kobj:	kobject for sysfs resources
+ * @obj_list:	head of list for struct klp_object
  * @enabled:	the patch is enabled (but operation may be incomplete)
  * @finish:	for waiting till it is safe to remove the patch module
  */
@@ -126,18 +134,25 @@ struct klp_patch {
 	/* internal */
 	struct list_head list;
 	struct kobject kobj;
+	struct list_head obj_list;
 	bool enabled;
 	struct completion finish;
 };
 
-#define klp_for_each_object(patch, obj) \
+#define klp_for_each_object_static(patch, obj) \
 	for (obj = patch->objs; obj->funcs || obj->name; obj++)
 
-#define klp_for_each_func(obj, func) \
+#define klp_for_each_object(patch, obj)	\
+	list_for_each_entry(obj, &patch->obj_list, obj_entry)
+
+#define klp_for_each_func_static(obj, func) \
 	for (func = obj->funcs; \
 	     func->old_name || func->new_func || func->old_sympos; \
 	     func++)
 
+#define klp_for_each_func(obj, func)	\
+	list_for_each_entry(func, &obj->func_list, func_entry)
+
 int klp_register_patch(struct klp_patch *);
 int klp_unregister_patch(struct klp_patch *);
 int klp_enable_patch(struct klp_patch *);
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index b9628e4..b7f77be 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -608,6 +608,7 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 	INIT_LIST_HEAD(&func->stack_node);
 	func->patched = false;
 	func->transition = false;
+	list_add(&func->func_entry, &obj->func_list);
 
 	/* The format for the sysfs directory is <function,sympos> where sympos
 	 * is the nth occurrence of this symbol in kallsyms for the patched
@@ -689,7 +690,9 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 	if (ret)
 		return ret;
 
-	klp_for_each_func(obj, func) {
+	list_add(&obj->obj_entry, &patch->obj_list);
+	INIT_LIST_HEAD(&obj->func_list);
+	klp_for_each_func_static(obj, func) {
 		ret = klp_init_func(obj, func);
 		if (ret)
 			goto free;
@@ -729,7 +732,8 @@ static int klp_init_patch(struct klp_patch *patch)
 		return ret;
 	}
 
-	klp_for_each_object(patch, obj) {
+	INIT_LIST_HEAD(&patch->obj_list);
+	klp_for_each_object_static(patch, obj) {
 		ret = klp_init_object(patch, obj);
 		if (ret)
 			goto free;
-- 
2.6.1