From d0807da78e11d46f18399cbf8c4028c731346766 Mon Sep 17 00:00:00 2001 From: Miroslav Benes Date: Wed, 10 Jan 2018 11:01:28 +0100 Subject: livepatch: Remove immediate feature Immediate flag has been used to disable per-task consistency and patch all tasks immediately. It could be useful if the patch doesn't change any function or data semantics. However, it causes problems on its own. The consistency problem is currently broken with respect to immediate patches. func a patches 1i 2i 3 When the patch 3 is applied, only 2i function is checked (by stack checking facility). There might be a task sleeping in 1i though. Such task is migrated to 3, because we do not check 1i in klp_check_stack_func() at all. Coming atomic replace feature would be easier to implement and more reliable without immediate. Thus, remove immediate feature completely and save us from the problems. Note that force feature has the similar problem. However it is considered as a last resort. If used, administrator should not apply any new live patches and should plan for reboot into an updated kernel. The architectures would now need to provide HAVE_RELIABLE_STACKTRACE to fully support livepatch. Signed-off-by: Miroslav Benes Acked-by: Josh Poimboeuf Signed-off-by: Jiri Kosina --- kernel/livepatch/core.c | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-) (limited to 'kernel/livepatch/core.c') diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 1c3c9b27c916..41be6061b92f 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -366,11 +366,6 @@ static int __klp_enable_patch(struct klp_patch *patch) /* * A reference is taken on the patch module to prevent it from being * unloaded. - * - * Note: For immediate (no consistency model) patches we don't allow - * patch modules to unload since there is no safe/sane method to - * determine if a thread is still running in the patched code contained - * in the patch module once the ftrace registration is successful. */ if (!try_module_get(patch->mod)) return -ENODEV; @@ -890,12 +885,7 @@ int klp_register_patch(struct klp_patch *patch) if (!klp_initialized()) return -ENODEV; - /* - * Architectures without reliable stack traces have to set - * patch->immediate because there's currently no way to patch kthreads - * with the consistency model. - */ - if (!klp_have_reliable_stack() && !patch->immediate) { + if (!klp_have_reliable_stack()) { pr_err("This architecture doesn't have support for the livepatch consistency model.\n"); return -ENOSYS; } -- cgit v1.2.3-59-g8ed1b