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livepatch: add (un)patch callbacks

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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>
This commit is contained in:
Joe Lawrence 2017-10-13 15:08:41 -04:00 • committed by Jiri Kosina
parent 19205da6a0
commit 93862e385d
10 changed files with 1091 additions and 13 deletions
Download patch file Download diff file Expand all files Collapse all files

51
kernel/livepatch/core.c
View file

@ -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);