Documentation: livepatch: Add livepatch API page

The livepatch subsystem has several exported functions and objects with
kerneldoc comments. Though the livepatch documentation contains handwritten
descriptions of all of these exported functions, they are currently not
pulled into the docs build using the kernel-doc directive.

In order to allow readers of the documentation to see the full kerneldoc
comments in the generated documentation files, this change adds a new
Documentation/livepatch/api.rst page which contains kernel-doc directives
to link the kerneldoc comments directly in the documentation.  With this,
all of the hand-written descriptions of the APIs now cross-reference the
kerneldoc comments on the new Livepatching APIs page, and running
./scripts/find-unused-docs.sh on kernel/livepatch no longer shows any files
as missing documentation.

Note that all of the handwritten API descriptions were left alone with the
exception of Documentation/livepatch/system-state.rst, which was updated to
allow the cross-referencing to work correctly. The file now follows the
cross-referencing formatting guidance specified in
Documentation/doc-guide/kernel-doc.rst. Furthermore, some comments around
klp_shadow_free_all() were updated to say <_, id> rather than <*, id> to
match the rest of the file, and to prevent the docs build from emitting an
"Inline emphasis start-string without end string" error.

Signed-off-by: David Vernet <void@manifault.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20211221145743.4098360-1-void@manifault.com

Documentation/livepatch/api.rst

@@ -0,0 +1,30 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+Livepatching APIs
+=================
+
+Livepatch Enablement
+====================
+
+.. kernel-doc:: kernel/livepatch/core.c
+   :export:
+
+
+Shadow Variables
+================
+
+.. kernel-doc:: kernel/livepatch/shadow.c
+   :export:
+
+System State Changes
+====================
+
+.. kernel-doc:: kernel/livepatch/state.c
+   :export:
+
+Object Types
+============
+
+.. kernel-doc:: include/linux/livepatch.h
+   :identifiers: klp_patch klp_object klp_func klp_callbacks klp_state

Documentation/livepatch/index.rst

@@ -14,6 +14,7 @@ Kernel Livepatching
     shadow-vars
     system-state
     reliable-stacktrace
+    api
 
 .. only::  subproject and html
 

Documentation/livepatch/shadow-vars.rst

@@ -82,8 +82,8 @@ to do actions that can be done only once when a new variable is allocated.
       - call destructor function if defined
       - free shadow variable
 
-* klp_shadow_free_all() - detach and free all <*, id> shadow variables
+* klp_shadow_free_all() - detach and free all <_, id> shadow variables
-  - find and remove any <*, id> references from global hashtable
+  - find and remove any <_, id> references from global hashtable
 
     - if found
 

Documentation/livepatch/system-state.rst

@@ -52,12 +52,12 @@ struct klp_state:
 
 The state can be manipulated using two functions:
 
-  - *klp_get_state(patch, id)*
+  - klp_get_state()
 
     - Get struct klp_state associated with the given livepatch
       and state id.
 
-  - *klp_get_prev_state(id)*
+  - klp_get_prev_state()
 
     - Get struct klp_state associated with the given feature id and
       already installed livepatches.

kernel/livepatch/shadow.c

@@ -272,12 +272,12 @@ void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor)
 EXPORT_SYMBOL_GPL(klp_shadow_free);
 
 /**
- * klp_shadow_free_all() - detach and free all <*, id> shadow variables
+ * klp_shadow_free_all() - detach and free all <_, id> shadow variables
  * @id:		data identifier
  * @dtor:	custom callback that can be used to unregister the variable
  *		and/or free data that the shadow variable points to (optional)
  *
- * This function releases the memory for all <*, id> shadow variable
+ * This function releases the memory for all <_, id> shadow variable
  * instances, callers should stop referencing them accordingly.
  */
 void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor)
@@ -288,7 +288,7 @@ void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor)
 
 	spin_lock_irqsave(&klp_shadow_lock, flags);
 
-	/* Delete all <*, id> from hash */
+	/* Delete all <_, id> from hash */
 	hash_for_each(klp_shadow_hash, i, shadow, node) {
 		if (klp_shadow_match(shadow, shadow->obj, id))
 			klp_shadow_free_struct(shadow, dtor);