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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 EACC3C3F2D2 for ; Thu, 5 Mar 2020 18:51:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB6CC20716 for ; Thu, 5 Mar 2020 18:51:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583434306; bh=ZC3B/czm5sXyN+zg1eniDW4R7/IH4E7e99uEpDEQv3k=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=FjDGFZ3der+I3+vdWI160JNiK+pYnczQbbmGYP3W5IFQELFwFELwEu1S3NvTmHqsH Y0npqzqXQbGYKp/5dwGuLra6prTKeueLwJ9b7t2b8ebLD7zIx/Q1v/YNQ0Ys3Z8Jyt 1t1pCl3MbpsSL30I14N/iPjOcw5WoZsz9sBE/N48= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726390AbgCESvp (ORCPT ); Thu, 5 Mar 2020 13:51:45 -0500 Received: from mail-io1-f65.google.com ([209.85.166.65]:37012 "EHLO mail-io1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725946AbgCESvp (ORCPT ); Thu, 5 Mar 2020 13:51:45 -0500 Received: by mail-io1-f65.google.com with SMTP id k4so2116035ior.4 for ; Thu, 05 Mar 2020 10:51:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=FVv6AJd6bBrTXrDKZfvcwskLDNuykZnEwGxDnO6gleo=; b=NosQg/dDBPylczuOudsaCOt2Wy3lcV1PT7hKYOVRoSkfJ+eNlJfzNDp8iKCEPyabBs 7ijGVjmDDkVeHS+mphZq8yulaRZIrDr0ERC2vSfh5WEDhfJi0aWFUsuDUCABp1zGL29i GzZi3kYiPM96HwrrhGF/bVmIWhCcRegdRwoRg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=FVv6AJd6bBrTXrDKZfvcwskLDNuykZnEwGxDnO6gleo=; b=W5ueEf+2TH3S5R6FZnV4n71YEChhvvwd50SN2dLVfc0PXmnUlm6z+qpdESi5qM0hH4 diFRmkcju6n1+7cxTW7ju2qXkZ9Sf23y9tqOccQGtdClADJ0LNDiwtl5NcKB+J3UTGQC F0/ZDDDVzW6cNfmycxDzTQXbfSg7rL5ECOQFITYf/wn28iU4gfcuK5GLVBKkTlv3/MS8 lDDxgQ2ufj6Hzct98DFJ4WjRAhCnyXODI9EhiTT5x8b0Qlb+lnIg5Bj9rQGVoiFaqb37 AeNFLJtUDtXOa3ZiWmVDDFgBMTxvJJdMMOe2hAfgYN4JyuIweDewq5/ifVOQT46Aq99q nbbA== X-Gm-Message-State: ANhLgQ2/JU5JwGpmK8wxHBCmt4m87W/6Fe5ZiHYWeCCZB+r6fGPGHwIA ebP9M9p+8qFgC7w/O3fsuwvoSRUrHy56XZaweHQTgg== X-Google-Smtp-Source: ADFU+vsbcs2QgeYXIqkD+c4bTE0VoOgWuVE+so2YReoLzqoxVPopVlkOtVPt0fcQ4lBq2p8/yZ+g4Aa9dVjEkBhbM+c= X-Received: by 2002:a6b:ec05:: with SMTP id c5mr376507ioh.107.1583434304466; Thu, 05 Mar 2020 10:51:44 -0800 (PST) MIME-Version: 1.0 References: <20200304124707.22650-1-yanaijie@huawei.com> <202003041022.26AF0178@keescook> In-Reply-To: From: Linus Torvalds Date: Thu, 5 Mar 2020 12:51:33 -0600 Message-ID: Subject: Re: [PATCH v3 0/6] implement KASLR for powerpc/fsl_booke/64 To: Scott Wood Cc: Kees Cook , Jason Yan , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , lkml , "Tobin C . Harding" , Daniel Axtens Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 4, 2020 at 3:16 PM Scott Wood wrote: > > The frustration is with the inability to set a flag to say, "I'm debugging and > don't care about leaks... in fact I'd like as much information as possible to > leak to me." Well, I definitely don't want to tie it to "I turned off kaslr in order to help debugging". That just means that now you're debugging a kernel that is fundamentally different from what people are running. So I'd much rather have people just set a really magic flag, perhaps when kgdb is in use or something. > In any case, this came up now due to a question about what to use when > printing crash dumps. PowerPC currently prints stack and return addresses > with %lx (in addition to %pS in the latter case) and someone proposed > converting them to %p and/or removing them altogether. Please just use '%pS'. The symbol and offset is what is useful when users send crash-dumps. The hex value is entirely pointless with kaslr - which should basically be the default. Note that this isn't about security at that point - crash dumps are something that shouldn't happen, but if they do happen, we want the pointers. But the random hex value just isn't _useful_, so it's just making things less legible. Linus