Merge tag 'livepatching-for-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching

Pull livepatching updates from Petr Mladek:

 - New API to track system state changes done be livepatch callbacks. It
   helps to maintain compatibility between livepatches.

 - Update Kconfig help text. ORC is another reliable unwinder.

 - Disable generic selftest timeout. Livepatch selftests have their own
   per-operation fine-grained timeouts.

* tag 'livepatching-for-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching:
  x86/stacktrace: update kconfig help text for reliable unwinders
  livepatch: Selftests of the API for tracking system state changes
  livepatch: Documentation of the new API for tracking system state changes
  livepatch: Allow to distinguish different version of system state changes
  livepatch: Basic API to track system state changes
  livepatch: Keep replaced patches until post_patch callback is called
  selftests/livepatch: Disable the timeout

1 files changed, 34 insertions, 10 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index ab4a4606d19b..c3512e7e0801 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -22,6 +22,7 @@
 #include <asm/cacheflush.h>
 #include "core.h"
 #include "patch.h"
+#include "state.h"
 #include "transition.h"
 
 /*
@@ -632,7 +633,7 @@ static void klp_free_objects_dynamic(struct klp_patch *patch)
  * The operation must be completed by calling klp_free_patch_finish()
  * outside klp_mutex.
  */
-void klp_free_patch_start(struct klp_patch *patch)
+static void klp_free_patch_start(struct klp_patch *patch)
 {
 	if (!list_empty(&patch->list))
 		list_del(&patch->list);
@@ -677,6 +678,23 @@ static void klp_free_patch_work_fn(struct work_struct *work)
 	klp_free_patch_finish(patch);
 }
 
+void klp_free_patch_async(struct klp_patch *patch)
+{
+	klp_free_patch_start(patch);
+	schedule_work(&patch->free_work);
+}
+
+void klp_free_replaced_patches_async(struct klp_patch *new_patch)
+{
+	struct klp_patch *old_patch, *tmp_patch;
+
+	klp_for_each_patch_safe(old_patch, tmp_patch) {
+		if (old_patch == new_patch)
+			return;
+		klp_free_patch_async(old_patch);
+	}
+}
+
 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 {
 	if (!func->old_name)
@@ -992,6 +1010,13 @@ int klp_enable_patch(struct klp_patch *patch)
 
 	mutex_lock(&klp_mutex);
 
+	if (!klp_is_patch_compatible(patch)) {
+		pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
+			patch->mod->name);
+		mutex_unlock(&klp_mutex);
+		return -EINVAL;
+	}
+
 	ret = klp_init_patch_early(patch);
 	if (ret) {
 		mutex_unlock(&klp_mutex);
@@ -1022,12 +1047,13 @@ err:
 EXPORT_SYMBOL_GPL(klp_enable_patch);
 
 /*
- * This function removes replaced patches.
+ * This function unpatches objects from the replaced livepatches.
  *
  * We could be pretty aggressive here. It is called in the situation where
- * these structures are no longer accessible. All functions are redirected
- * by the klp_transition_patch. They use either a new code or they are in
- * the original code because of the special nop function patches.
+ * these structures are no longer accessed from the ftrace handler.
+ * All functions are redirected by the klp_transition_patch. They
+ * use either a new code or they are in the original code because
+ * of the special nop function patches.
  *
  * The only exception is when the transition was forced. In this case,
  * klp_ftrace_handler() might still see the replaced patch on the stack.
@@ -1035,18 +1061,16 @@ EXPORT_SYMBOL_GPL(klp_enable_patch);
  * thanks to RCU. We only have to keep the patches on the system. Also
  * this is handled transparently by patch->module_put.
  */
-void klp_discard_replaced_patches(struct klp_patch *new_patch)
+void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
 {
-	struct klp_patch *old_patch, *tmp_patch;
+	struct klp_patch *old_patch;
 
-	klp_for_each_patch_safe(old_patch, tmp_patch) {
+	klp_for_each_patch(old_patch) {
 		if (old_patch == new_patch)
 			return;
 
 		old_patch->enabled = false;
 		klp_unpatch_objects(old_patch);
-		klp_free_patch_start(old_patch);
-		schedule_work(&old_patch->free_work);
 	}
 }