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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 E0891C43141 for ; Wed, 20 Jun 2018 23:22:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9D94320652 for ; Wed, 20 Jun 2018 23:22:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=tobin.cc header.i=@tobin.cc header.b="SK7uULWv"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="OwFcYjyA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D94320652 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=tobin.cc Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932431AbeFTXWj (ORCPT ); Wed, 20 Jun 2018 19:22:39 -0400 Received: from out2-smtp.messagingengine.com ([66.111.4.26]:34143 "EHLO out2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754339AbeFTXWi (ORCPT ); Wed, 20 Jun 2018 19:22:38 -0400 Received: from compute5.internal (compute5.nyi.internal [10.202.2.45]) by mailout.nyi.internal (Postfix) with ESMTP id 8FCE421B98; Wed, 20 Jun 2018 19:22:37 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute5.internal (MEProxy); Wed, 20 Jun 2018 19:22:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tobin.cc; h=cc :content-type:date:from:in-reply-to:message-id:mime-version :references:subject:to:x-me-sender:x-me-sender:x-sasl-enc; s= fm3; bh=oAijAKVrsOvMXbmBw8Geq9oGa3XeT4mkjrnu0RPVmRI=; b=SK7uULWv LW8/QihrtjF1wTY72tz6QKrdlVwBvbFBGePns0WcVqnraOHS4UmDaOU5oK8ojquo zzxYsFK/qcYHUdGbwWZfrGq+kpRkQ5A1c/aumgS6RgmDBetSCqgHLmKbb0tfKKGb Phq2mX3foFcotvXuNkbvf5gxg8v8q/uWN+B2EZJVvUaOxpbFjzddQ98KCdSIa4al 7iWH4CsI0VZtLYUsgtvrYbLUXy07k7xiy3XF6vcQRzrmssgo8ku59L0DgdVw1rXt 0aImV0JK4dL6+N7p/zYeLS5Vc6xw9AeTDtONyIgo3spkHROcmzCh5bGOV60pkVpD ZsIJbPE1azPp2A== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-sender :x-me-sender:x-sasl-enc; s=fm3; bh=oAijAKVrsOvMXbmBw8Geq9oGa3XeT 4mkjrnu0RPVmRI=; b=OwFcYjyAepCAsmmJgmL03C2z8aOB4ulLpWI3ZV5IS6Mqr I8xUrP3wtkyHiO7v2j2JZyaQBjh18faZTOV80rUBk4u23C7a9+i7O1UsdyXu8Tlo EtqQPJuhJvR/daCsXrd5W8Pn/jTKpGUdb2quvBVJA1MxgvkVxdX+w7ckk1xsv075 RiaXvIeukyMiwW/MEwO6wmSgQB86nLOlwYAOPwv6K1wDojdXfabX2DDbRjJEANm+ lByUhvGcda1t4xXSUi7LFj6jcpFWZ+UmficZ/E9xJh5N7V5KDL9xfALDEDIrTp/s 7mvG8chIOnX4JZZhiFddmyfqmdz9AzsTfO82QMS6Q== X-ME-Proxy: X-ME-Sender: Received: from localhost (124-171-16-226.dyn.iinet.net.au [124.171.16.226]) by mail.messagingengine.com (Postfix) with ESMTPA id 76832E446F; Wed, 20 Jun 2018 19:22:36 -0400 (EDT) Date: Thu, 21 Jun 2018 09:22:33 +1000 From: "Tobin C. Harding" To: Randy Dunlap Cc: Theodore Ts'o , Linus Torvalds , Steven Rostedt , Kees Cook , Anna-Maria Gleixner , Andrew Morton , Greg Kroah-Hartman , Arnd Bergmann , Andy Shevchenko , linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 4/4] vsprintf: Add command line option debug_boot_weak_hash Message-ID: <20180620232233.GH11671@eros> References: <20180620042046.30806-1-me@tobin.cc> <20180620042046.30806-5-me@tobin.cc> <20180620223014.GE11671@eros> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailer: Mutt 1.9.4 (2018-02-28) User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 20, 2018 at 03:36:44PM -0700, Randy Dunlap wrote: > On 06/20/2018 03:30 PM, Tobin C. Harding wrote: > > On Wed, Jun 20, 2018 at 09:09:49AM -0700, Randy Dunlap wrote: > >> On 06/19/2018 09:20 PM, Tobin C. Harding wrote: > >>> Currently printing [hashed] pointers requires enough entropy to be > >>> available. Early in the boot sequence this may not be the case > >>> resulting in a dummy string '(____ptrval____)' being printed. This > >>> makes debugging the early boot sequence difficult. We can relax the > >>> requirement to use cryptographically secure hashing during debugging. > >>> This enables debugging while keeping development/production kernel > >>> behaviour the same. > >>> > >>> If new command line option debug_boot_weak_hash is enabled use > >>> cryptographically insecure hashing and hash pointer value immediately. > >>> > >>> Signed-off-by: Tobin C. Harding > >>> Reviewed-by: Steven Rostedt (VMware) > >>> --- > >>> Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++ > >>> lib/vsprintf.c | 17 +++++++++++++++++ > >>> 2 files changed, 26 insertions(+) > >>> > >>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > >>> index 638342d0a095..a116fc0366b0 100644 > >>> --- a/Documentation/admin-guide/kernel-parameters.txt > >>> +++ b/Documentation/admin-guide/kernel-parameters.txt > >>> @@ -748,6 +748,15 @@ > >>> > >>> debug [KNL] Enable kernel debugging (events log level). > >>> > >>> + debug_boot_weak_hash > >>> + [KNL] Enable printing pointers early in the boot > >>> + sequence. If enabled, we use a weak hash instead of > >>> + siphash to hash pointers. Use this option if you need > >>> + to see pointer values during early boot (i.e you are > >> > >> maybe: > >> to see hashed pointer values > >> i.e., not raw pointers. > > > > You cannot see 'raw pointers' anyways? > > only if using %px ? > > Maybe it's just terminology. I don't consider a hashed value as a pointer value. > It's just a key or handle or some other number, but it's not a pointer. > > >> > >>> + seeing instances of '(___ptrval___)'). > >>> + Cryptographically insecure, please do not use on > >>> + production kernels. > > > > thanks for the review, I don't quiet see how to use your suggestion to > > make the text clearer. If you still feel this change is needed perhaps > > you could write so I understand i.e 'Use this option if ...' > > > OK, if you are good with it, I am too. :) I get you know. I agree, how about this [KNL] Enable printing pointers early in the boot sequence. If enabled, we use a weak hash instead of siphash to hash pointers. Use this option if you need to print pointers with %px during early boot (i.e you are seeing instances of '(___ptrval___)'). Cryptographically insecure, please do not use on production kernels. thanks for clarifying, Tobin.