1. Move klp_ops into klp_func structure.
Rewrite the logic of klp_find_ops and
other logic to get klp_ops of a function.

2. Move definition of struct klp_ops into
include/linux/livepatch.h

Signed-off-by: Wardenjohn <zhangwarden@gmail.com>

diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 51a258c24ff5..d874aecc817b 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -22,6 +22,25 @@
 #define KLP_TRANSITION_UNPATCHED	 0
 #define KLP_TRANSITION_PATCHED		 1
 
+/**
+ * struct klp_ops - structure for tracking registered ftrace ops structs
+ *
+ * A single ftrace_ops is shared between all enabled replacement functions
+ * (klp_func structs) which have the same old_func.  This allows the switch
+ * between function versions to happen instantaneously by updating the klp_ops
+ * struct's func_stack list.  The winner is the klp_func at the top of the
+ * func_stack (front of the list).
+ *
+ * @node:	node for the global klp_ops list
+ * @func_stack:	list head for the stack of klp_func's (active func is on top)
+ * @fops:	registered ftrace ops struct
+ */
+struct klp_ops {
+	struct list_head node;
+	struct list_head func_stack;
+	struct ftrace_ops fops;
+};
+
 /**
  * struct klp_func - function structure for live patching
  * @old_name:	name of the function to be patched
@@ -32,6 +51,7 @@
  * @kobj:	kobject for sysfs resources
  * @node:	list node for klp_object func_list
  * @stack_node:	list node for klp_ops func_stack list
+ * @ops:	pointer to klp_ops struct for this function
  * @old_size:	size of the old function
  * @new_size:	size of the new function
  * @nop:        temporary patch to use the original code again; dyn. allocated
@@ -71,6 +91,7 @@ struct klp_func {
 	struct kobject kobj;
 	struct list_head node;
 	struct list_head stack_node;
+	struct klp_ops *ops;
 	unsigned long old_size, new_size;
 	bool nop;
 	bool patched;
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 52426665eecc..e4572bf34316 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -760,6 +760,8 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 	if (!func->old_name)
 		return -EINVAL;
 
+	func->ops = NULL;
+
 	/*
 	 * NOPs get the address later. The patched module must be loaded,
 	 * see klp_init_object_loaded().
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index 90408500e5a3..8ab9c35570f4 100644
--- a/kernel/livepatch/patch.c
+++ b/kernel/livepatch/patch.c
@@ -20,18 +20,25 @@
 #include "patch.h"
 #include "transition.h"
 
-static LIST_HEAD(klp_ops);
 
 struct klp_ops *klp_find_ops(void *old_func)
 {
-	struct klp_ops *ops;
+	struct klp_patch *patch;
+	struct klp_object *obj;
 	struct klp_func *func;
 
-	list_for_each_entry(ops, &klp_ops, node) {
-		func = list_first_entry(&ops->func_stack, struct klp_func,
-					stack_node);
-		if (func->old_func == old_func)
-			return ops;
+	klp_for_each_patch(patch) {
+		klp_for_each_object(patch, obj) {
+			klp_for_each_func(obj, func) {
+				/*
+				 * Ignore entry where func->ops has not been
+				 * assigned yet. It is most likely the one
+				 * which is about to be created/added.
+				 */
+				if (func->old_func == old_func && func->ops)
+					return func->ops;
+			}
+		}
 	}
 
 	return NULL;
@@ -133,7 +140,7 @@ static void klp_unpatch_func(struct klp_func *func)
 	if (WARN_ON(!func->old_func))
 		return;
 
-	ops = klp_find_ops(func->old_func);
+	ops = func->ops;
 	if (WARN_ON(!ops))
 		return;
 
@@ -149,6 +156,7 @@ static void klp_unpatch_func(struct klp_func *func)
 
 		list_del_rcu(&func->stack_node);
 		list_del(&ops->node);
+		func->ops = NULL;
 		kfree(ops);
 	} else {
 		list_del_rcu(&func->stack_node);
@@ -168,7 +176,7 @@ static int klp_patch_func(struct klp_func *func)
 	if (WARN_ON(func->patched))
 		return -EINVAL;
 
-	ops = klp_find_ops(func->old_func);
+	ops = func->ops;
 	if (!ops) {
 		unsigned long ftrace_loc;
 
@@ -191,8 +199,6 @@ static int klp_patch_func(struct klp_func *func)
 				  FTRACE_OPS_FL_IPMODIFY |
 				  FTRACE_OPS_FL_PERMANENT;
 
-		list_add(&ops->node, &klp_ops);
-
 		INIT_LIST_HEAD(&ops->func_stack);
 		list_add_rcu(&func->stack_node, &ops->func_stack);
 
@@ -211,7 +217,7 @@ static int klp_patch_func(struct klp_func *func)
 			goto err;
 		}
 
-
+		func->ops = ops;
 	} else {
 		list_add_rcu(&func->stack_node, &ops->func_stack);
 	}
@@ -224,6 +230,7 @@ static int klp_patch_func(struct klp_func *func)
 	list_del_rcu(&func->stack_node);
 	list_del(&ops->node);
 	kfree(ops);
+	func->ops = NULL;
 	return ret;
 }
 
diff --git a/kernel/livepatch/patch.h b/kernel/livepatch/patch.h
index d5f2fbe373e0..21d0d20b7189 100644
--- a/kernel/livepatch/patch.h
+++ b/kernel/livepatch/patch.h
@@ -6,25 +6,6 @@
 #include <linux/list.h>
 #include <linux/ftrace.h>
 
-/**
- * struct klp_ops - structure for tracking registered ftrace ops structs
- *
- * A single ftrace_ops is shared between all enabled replacement functions
- * (klp_func structs) which have the same old_func.  This allows the switch
- * between function versions to happen instantaneously by updating the klp_ops
- * struct's func_stack list.  The winner is the klp_func at the top of the
- * func_stack (front of the list).
- *
- * @node:	node for the global klp_ops list
- * @func_stack:	list head for the stack of klp_func's (active func is on top)
- * @fops:	registered ftrace ops struct
- */
-struct klp_ops {
-	struct list_head node;
-	struct list_head func_stack;
-	struct ftrace_ops fops;
-};
-
 struct klp_ops *klp_find_ops(void *old_func);
 
 int klp_patch_object(struct klp_object *obj);
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index ba069459c101..d9a3f9c7a93b 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -230,7 +230,7 @@ static int klp_check_stack_func(struct klp_func *func, unsigned long *entries,
 		 * Check for the to-be-patched function
 		 * (the previous func).
 		 */
-		ops = klp_find_ops(func->old_func);
+		ops = func->ops;
 
 		if (list_is_singular(&ops->func_stack)) {
 			/* original function */
-- 
2.18.2

On Thu, Aug 22, 2024 at 11:01:58AM +0800, Wardenjohn wrote:
> 1. Move klp_ops into klp_func structure.
> Rewrite the logic of klp_find_ops and
> other logic to get klp_ops of a function.
> 
> 2. Move definition of struct klp_ops into
> include/linux/livepatch.h

Why?

> On Aug 25, 2024, at 12:48, Christoph Hellwig <hch@infradead.org> wrote:
> 
> On Thu, Aug 22, 2024 at 11:01:58AM +0800, Wardenjohn wrote:
>> 1. Move klp_ops into klp_func structure.
>> Rewrite the logic of klp_find_ops and
>> other logic to get klp_ops of a function.
>> 
>> 2. Move definition of struct klp_ops into
>> include/linux/livepatch.h
> 
> Why?
> 

Hi, Christoph.

When introducing feature of "using", we should handle the klp_ops check.
In order to get klp_ops from transition, we may have more complex logic for 
checking.

If we move klp_ops into klp_func. We can remove the global list head of klp_ops.
What's more, there are some code in livepatch should get function's ops.
With this feature, we don't need the original search to the one ops.
It can be simple and straightforward.

Regards,
Wardenjohn

On Sun, 25 Aug 2024, zhang warden wrote:

> >> 1. Move klp_ops into klp_func structure.
> >> Rewrite the logic of klp_find_ops and
> >> other logic to get klp_ops of a function.
> >> 
> >> 2. Move definition of struct klp_ops into
> >> include/linux/livepatch.h
> > 
> > Why?
> > 
> 
> Hi, Christoph.
> 
> When introducing feature of "using", we should handle the klp_ops check.
> In order to get klp_ops from transition, we may have more complex logic for 
> checking.
> 
> If we move klp_ops into klp_func. We can remove the global list head of klp_ops.
> What's more, there are some code in livepatch should get function's ops.
> With this feature, we don't need the original search to the one ops.
> It can be simple and straightforward.

I believe that Christoph's "Why?" in fact meant "please include the 
rationale for the changes being made (such as the above) in the patch 
changelog" :)

Thanks,

-- 
Jiri Kosina
SUSE Labs

> On Aug 26, 2024, at 04:17, Jiri Kosina <jikos@kernel.org> wrote:
> 
> I believe that Christoph's "Why?" in fact meant "please include the 
> rationale for the changes being made (such as the above) in the patch 
> changelog" :)
> 
> Thanks,
> 
> -- 
> Jiri Kosina
> SUSE Labs
> 

Hi Kosina.

OK, the relation on this patch will update into the commit log in next version.

Thanks,
Wardenjohn.