livepatch: add (un)patch callbacks
Provide livepatch modules a klp_object (un)patching notification
mechanism. Pre and post-(un)patch callbacks allow livepatch modules to
setup or synchronize changes that would be difficult to support in only
patched-or-unpatched code contexts.
Callbacks can be registered for target module or vmlinux klp_objects,
but each implementation is klp_object specific.
- Pre-(un)patch callbacks run before any (un)patching transition
starts.
- Post-(un)patch callbacks run once an object has been (un)patched and
the klp_patch fully transitioned to its target state.
Example use cases include modification of global data and registration
of newly available services/handlers.
See Documentation/livepatch/callbacks.txt for details and
samples/livepatch/ for examples.
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index b9628e4..cafb5a8 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -54,11 +54,6 @@ static bool klp_is_module(struct klp_object *obj)
return obj->name;
}
-static bool klp_is_object_loaded(struct klp_object *obj)
-{
- return !obj->name || obj->mod;
-}
-
/* sets obj->mod if object is not vmlinux and module is found */
static void klp_find_object_module(struct klp_object *obj)
{
@@ -285,6 +280,8 @@ static int klp_write_object_relocations(struct module *pmod,
static int __klp_disable_patch(struct klp_patch *patch)
{
+ struct klp_object *obj;
+
if (klp_transition_patch)
return -EBUSY;
@@ -295,6 +292,10 @@ static int __klp_disable_patch(struct klp_patch *patch)
klp_init_transition(patch, KLP_UNPATCHED);
+ klp_for_each_object(patch, obj)
+ if (patch->enabled && obj->patched)
+ klp_pre_unpatch_callback(obj);
+
/*
* Enforce the order of the func->transition writes in
* klp_init_transition() and the TIF_PATCH_PENDING writes in
@@ -388,13 +389,18 @@ static int __klp_enable_patch(struct klp_patch *patch)
if (!klp_is_object_loaded(obj))
continue;
+ ret = klp_pre_patch_callback(obj);
+ if (ret) {
+ pr_warn("pre-patch callback failed for object '%s'\n",
+ klp_is_module(obj) ? obj->name : "vmlinux");
+ goto err;
+ }
+
ret = klp_patch_object(obj);
if (ret) {
- pr_warn("failed to enable patch '%s'\n",
- patch->mod->name);
-
- klp_cancel_transition();
- return ret;
+ pr_warn("failed to patch object '%s'\n",
+ klp_is_module(obj) ? obj->name : "vmlinux");
+ goto err;
}
}
@@ -403,6 +409,11 @@ static int __klp_enable_patch(struct klp_patch *patch)
patch->enabled = true;
return 0;
+err:
+ pr_warn("failed to enable patch '%s'\n", patch->mod->name);
+
+ klp_cancel_transition();
+ return ret;
}
/**
@@ -871,13 +882,27 @@ int klp_module_coming(struct module *mod)
pr_notice("applying patch '%s' to loading module '%s'\n",
patch->mod->name, obj->mod->name);
+ ret = klp_pre_patch_callback(obj);
+ if (ret) {
+ pr_warn("pre-patch callback failed for object '%s'\n",
+ obj->name);
+ goto err;
+ }
+
ret = klp_patch_object(obj);
if (ret) {
pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
patch->mod->name, obj->mod->name, ret);
+
+ if (patch != klp_transition_patch)
+ klp_post_unpatch_callback(obj);
+
goto err;
}
+ if (patch != klp_transition_patch)
+ klp_post_patch_callback(obj);
+
break;
}
}
@@ -927,9 +952,15 @@ void klp_module_going(struct module *mod)
* is in transition.
*/
if (patch->enabled || patch == klp_transition_patch) {
+
+ if (patch != klp_transition_patch)
+ klp_pre_unpatch_callback(obj);
+
pr_notice("reverting patch '%s' on unloading module '%s'\n",
patch->mod->name, obj->mod->name);
klp_unpatch_object(obj);
+
+ klp_post_unpatch_callback(obj);
}
klp_free_object_loaded(obj);
diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h
index c74f24c..6fc907b 100644
--- a/kernel/livepatch/core.h
+++ b/kernel/livepatch/core.h
@@ -1,6 +1,44 @@
#ifndef _LIVEPATCH_CORE_H
#define _LIVEPATCH_CORE_H
+#include <linux/livepatch.h>
+
extern struct mutex klp_mutex;
+static inline bool klp_is_object_loaded(struct klp_object *obj)
+{
+ return !obj->name || obj->mod;
+}
+
+static inline int klp_pre_patch_callback(struct klp_object *obj)
+{
+ int ret;
+
+ ret = (obj->callbacks.pre_patch) ?
+ (*obj->callbacks.pre_patch)(obj) : 0;
+
+ obj->callbacks.post_unpatch_enabled = !ret;
+
+ return ret;
+}
+
+static inline void klp_post_patch_callback(struct klp_object *obj)
+{
+ if (obj->callbacks.post_patch)
+ (*obj->callbacks.post_patch)(obj);
+}
+
+static inline void klp_pre_unpatch_callback(struct klp_object *obj)
+{
+ if (obj->callbacks.pre_unpatch)
+ (*obj->callbacks.pre_unpatch)(obj);
+}
+
+static inline void klp_post_unpatch_callback(struct klp_object *obj)
+{
+ if (obj->callbacks.post_unpatch_enabled &&
+ obj->callbacks.post_unpatch)
+ (*obj->callbacks.post_unpatch)(obj);
+}
+
#endif /* _LIVEPATCH_CORE_H */
diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
index 52c4e90..82d5842 100644
--- a/kernel/livepatch/patch.c
+++ b/kernel/livepatch/patch.c
@@ -28,6 +28,7 @@
#include <linux/slab.h>
#include <linux/bug.h>
#include <linux/printk.h>
+#include "core.h"
#include "patch.h"
#include "transition.h"
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index b004a1f..7bf55b7 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -109,9 +109,6 @@ static void klp_complete_transition(void)
}
}
- if (klp_target_state == KLP_UNPATCHED && !immediate_func)
- module_put(klp_transition_patch->mod);
-
/* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */
if (klp_target_state == KLP_PATCHED)
klp_synchronize_transition();
@@ -130,6 +127,24 @@ static void klp_complete_transition(void)
}
done:
+ klp_for_each_object(klp_transition_patch, obj) {
+ if (!klp_is_object_loaded(obj))
+ continue;
+ if (klp_target_state == KLP_PATCHED)
+ klp_post_patch_callback(obj);
+ else if (klp_target_state == KLP_UNPATCHED)
+ klp_post_unpatch_callback(obj);
+ }
+
+ /*
+ * See complementary comment in __klp_enable_patch() for why we
+ * keep the module reference for immediate patches.
+ */
+ if (!klp_transition_patch->immediate && !immediate_func &&
+ klp_target_state == KLP_UNPATCHED) {
+ module_put(klp_transition_patch->mod);
+ }
+
klp_target_state = KLP_UNDEFINED;
klp_transition_patch = NULL;
}
