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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4383C38A2D for ; Mon, 24 Oct 2022 14:34:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232547AbiJXOeQ (ORCPT ); Mon, 24 Oct 2022 10:34:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237178AbiJXOeC (ORCPT ); Mon, 24 Oct 2022 10:34:02 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 611029DDB8 for ; Mon, 24 Oct 2022 06:09:08 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id AA2F21FD92; Mon, 24 Oct 2022 12:59:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1666616374; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=pN1heeaLFpPg/ZBDZe4BcH3XBZUjLc6e8rJPSmQsDEU=; b=PoL/fBmFXb6KN4l/Qlho0qFF9VKO+PynOA7kfR1D6YJ+4tqHXlXJDb0QgnpKaInEOragmJ kRpugBxwo6XODyX/JvKh7z44pSz+Qkh/4pbkVrsmnhMv99meJYuJ7Jvj+aLnDd6tW75b3+ pOIUPALlZcb2igg1hMT1I6Xdf4nGVao= Received: from suse.cz (unknown [10.100.201.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 8C7862C141; Mon, 24 Oct 2022 12:59:34 +0000 (UTC) Date: Mon, 24 Oct 2022 14:59:31 +0200 From: Petr Mladek To: Joe Lawrence Cc: Marcos Paulo de Souza , live-patching@vger.kernel.org, jpoimboe@redhat.com, mbenes@suse.cz, nstange@suse.de Subject: Re: [PATCH 3/4] livepatch/shadow: Introduce klp_shadow_type structure Message-ID: References: <20220701194817.24655-1-mpdesouza@suse.com> <20220701194817.24655-4-mpdesouza@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Thu 2022-08-25 10:50:20, Joe Lawrence wrote: > On 7/1/22 3:48 PM, Marcos Paulo de Souza wrote: > > The shadow variable type will be used in klp_shadow_alloc/get/free > > functions instead of id/ctor/dtor parameters. As a result, all callers > > use the same callbacks consistently[*][**]. > > > > The structure will be used in the next patch that will manage the > > lifetime of shadow variables and execute garbage collection automatically. > > > > [*] From the user POV, it might have been easier to pass $id instead > > of pointer to struct klp_shadow_type. > > > > The problem is that each livepatch registers its own struct > > klp_shadow_type and defines its own @ctor/@dtor callbacks. It would > > be unclear what callback should be used. They should be compatible. > > > > This problem is gone when each livepatch explicitly uses its > > own struct klp_shadow_type pointing to its own callbacks. > > > > [**] test_klp_shadow_vars.c uses a custom @dtor to show that it was called. > > The message must be disabled when called via klp_shadow_free_all() > > because the ordering of freed variables is not well defined there. > > It has to be done using another hack after switching to > > klp_shadow_types. > > > > Is the ordering problem new to this patchset? Shadow variables are > still saved in klp_shadow_hash and I think the only change in this patch > is that we need to compare through shadow_type and not id directly. Or > does patch 4/4 change behavior here? Just curious, otherwise this patch > is pretty straightforward. The problem is old. klp_shadow_free_all() uses hash_for_each(). It iterates the hashes sorted by the hash value. The tested arrays are on stack. The address of the stack is different in every run. As a result, the hash is always different and the pointers are sorted in different order. Best Regards, Petr