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livepatch/module: remove livepatch module notifier

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Remove the livepatch module notifier in favor of directly enabling and
disabling patches to modules in the module loader. Hard-coding the
function calls ensures that ftrace_module_enable() is run before
klp_module_coming() during module load, and that klp_module_going() is
run before ftrace_release_mod() during module unload. This way, ftrace
and livepatch code is run in the correct order during the module
load/unload sequence without dependence on the module notifier call chain.

Signed-off-by: Jessica Yu <jeyu@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Jessica Yu 2016-03-16 20:55:39 -04:00 • committed by Jiri Kosina
parent 4c973d1620
commit 7e545d6eca
3 changed files with 104 additions and 86 deletions
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167
kernel/livepatch/core.c
View file

@ -99,12 +99,12 @@ static void klp_find_object_module(struct klp_object *obj)
/*
* We do not want to block removal of patched modules and therefore
* we do not take a reference here. The patches are removed by
* a going module handler instead.
* klp_module_going() instead.
*/
mod = find_module(obj->name);
/*
* Do not mess work of the module coming and going notifiers.
* Note that the patch might still be needed before the going handler
* Do not mess work of klp_module_coming() and klp_module_going().
* Note that the patch might still be needed before klp_module_going()
* is called. Module functions can be called even in the GOING state
* until mod->exit() finishes. This is especially important for
* patches that modify semantic of the functions.
@ -866,88 +866,49 @@ int klp_register_patch(struct klp_patch *patch)
}
EXPORT_SYMBOL_GPL(klp_register_patch);
static int klp_module_notify_coming(struct klp_patch *patch,
struct klp_object *obj)
{
struct module *pmod = patch->mod;
struct module *mod = obj->mod;
int ret;
ret = klp_init_object_loaded(patch, obj);
if (ret) {
pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
pmod->name, mod->name, ret);
return ret;
}
if (patch->state == KLP_DISABLED)
return 0;
pr_notice("applying patch '%s' to loading module '%s'\n",
pmod->name, mod->name);
ret = klp_enable_object(obj);
if (ret)
pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
pmod->name, mod->name, ret);
return ret;
}
static void klp_module_notify_going(struct klp_patch *patch,
struct klp_object *obj)
{
struct module *pmod = patch->mod;
struct module *mod = obj->mod;
if (patch->state == KLP_DISABLED)
goto disabled;
pr_notice("reverting patch '%s' on unloading module '%s'\n",
pmod->name, mod->name);
klp_disable_object(obj);
disabled:
klp_free_object_loaded(obj);
}
static int klp_module_notify(struct notifier_block *nb, unsigned long action,
void *data)
int klp_module_coming(struct module *mod)
{
int ret;
struct module *mod = data;
struct klp_patch *patch;
struct klp_object *obj;
if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
return 0;
if (WARN_ON(mod->state != MODULE_STATE_COMING))
return -EINVAL;
mutex_lock(&klp_mutex);
/*
* Each module has to know that the notifier has been called.
* We never know what module will get patched by a new patch.
* Each module has to know that klp_module_coming()
* has been called. We never know what module will
* get patched by a new patch.
*/
if (action == MODULE_STATE_COMING)
mod->klp_alive = true;
else /* MODULE_STATE_GOING */
mod->klp_alive = false;
mod->klp_alive = true;
list_for_each_entry(patch, &klp_patches, list) {
klp_for_each_object(patch, obj) {
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
continue;
if (action == MODULE_STATE_COMING) {
obj->mod = mod;
ret = klp_module_notify_coming(patch, obj);
if (ret) {
obj->mod = NULL;
pr_warn("patch '%s' is in an inconsistent state!\n",
patch->mod->name);
}
} else /* MODULE_STATE_GOING */
klp_module_notify_going(patch, obj);
obj->mod = mod;
ret = klp_init_object_loaded(patch, obj);
if (ret) {
pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
patch->mod->name, obj->mod->name, ret);
goto err;
}
if (patch->state == KLP_DISABLED)
break;
pr_notice("applying patch '%s' to loading module '%s'\n",
patch->mod->name, obj->mod->name);
ret = klp_enable_object(obj);
if (ret) {
pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
patch->mod->name, obj->mod->name, ret);
goto err;
}
break;
}
@ -956,12 +917,56 @@ static int klp_module_notify(struct notifier_block *nb, unsigned long action,
mutex_unlock(&klp_mutex);
return 0;
err:
/*
* If a patch is unsuccessfully applied, return
* error to the module loader.
*/
pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
patch->mod->name, obj->mod->name, obj->mod->name);
mod->klp_alive = false;
klp_free_object_loaded(obj);
mutex_unlock(&klp_mutex);
return ret;
}
static struct notifier_block klp_module_nb = {
.notifier_call = klp_module_notify,
.priority = INT_MIN+1, /* called late but before ftrace notifier */
};
void klp_module_going(struct module *mod)
{
struct klp_patch *patch;
struct klp_object *obj;
if (WARN_ON(mod->state != MODULE_STATE_GOING &&
mod->state != MODULE_STATE_COMING))
return;
mutex_lock(&klp_mutex);
/*
* Each module has to know that klp_module_going()
* has been called. We never know what module will
* get patched by a new patch.
*/
mod->klp_alive = false;
list_for_each_entry(patch, &klp_patches, list) {
klp_for_each_object(patch, obj) {
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
continue;
if (patch->state != KLP_DISABLED) {
pr_notice("reverting patch '%s' on unloading module '%s'\n",
patch->mod->name, obj->mod->name);
klp_disable_object(obj);
}
klp_free_object_loaded(obj);
break;
}
}
mutex_unlock(&klp_mutex);
}
static int __init klp_init(void)
{
@ -973,21 +978,11 @@ static int __init klp_init(void)
return -EINVAL;
}
ret = register_module_notifier(&klp_module_nb);
if (ret)
return ret;
klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
if (!klp_root_kobj) {
ret = -ENOMEM;
goto unregister;
}
if (!klp_root_kobj)
return -ENOMEM;
return 0;
unregister:
unregister_module_notifier(&klp_module_nb);
return ret;
}
module_init(klp_init);