From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9F22CC10F0E for ; Thu, 18 Apr 2019 11:29:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C94B217FA for ; Thu, 18 Apr 2019 11:29:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388814AbfDRL3s (ORCPT ); Thu, 18 Apr 2019 07:29:48 -0400 Received: from mx2.suse.de ([195.135.220.15]:42558 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728074AbfDRL3r (ORCPT ); Thu, 18 Apr 2019 07:29:47 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id ABCCFAE60; Thu, 18 Apr 2019 11:29:46 +0000 (UTC) From: Petr Mladek To: Jiri Kosina , Josh Poimboeuf , Miroslav Benes Cc: Kamalesh Babulal , Joe Lawrence , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Petr Mladek Subject: [PATCH] livepatch: Convert error about unsupported reliable stacktrace into a warning Date: Thu, 18 Apr 2019 13:29:36 +0200 Message-Id: <20190418112936.13295-1-pmladek@suse.com> X-Mailer: git-send-email 2.16.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The commit d0807da78e11d46f ("livepatch: Remove immediate feature") caused that any livepatch was refused when reliable stacktraces were not supported on the given architecture. The limitation is too strong. User space processes are safely migrated even when entering or leaving the kernel. Kthreads transition would need to get forced. But it is safe when: + The livepatch does not change the semantic of the code. + Callbacks do not depend on a safely finished transition. Suggested-by: Josh Poimboeuf Signed-off-by: Petr Mladek --- kernel/livepatch/core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index eb0ee10a1981..14f33ab6c583 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -1003,11 +1003,10 @@ int klp_enable_patch(struct klp_patch *patch) return -ENODEV; if (!klp_have_reliable_stack()) { - pr_err("This architecture doesn't have support for the livepatch consistency model.\n"); - return -EOPNOTSUPP; + pr_warn("This architecture doesn't have support for the livepatch consistency model.\n"); + pr_warn("The livepatch transition may never complete.\n"); } - mutex_lock(&klp_mutex); ret = klp_init_patch_early(patch); -- 2.16.4