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 A513CC433FE for ; Tue, 11 Oct 2022 22:22:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229517AbiJKWWg (ORCPT ); Tue, 11 Oct 2022 18:22:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60930 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229529AbiJKWWf (ORCPT ); Tue, 11 Oct 2022 18:22:35 -0400 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C905192AD for ; Tue, 11 Oct 2022 15:22:34 -0700 (PDT) Received: by mail-pl1-x62c.google.com with SMTP id d24so14543976pls.4 for ; Tue, 11 Oct 2022 15:22:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=Ya+CrD6RQ5p1FsGwF6+V+S0eZMj0JP4hh6Oy/+hJ7f4=; b=EproxsXPwDwkz7NeJxiKx0xV5B+FL8MhUsL1YDElBzk+7TPFMlIrsgHkX7RW+4d1Rq 0IneH/P6OX5ynCTdW9Do+GL+NnRCveMX4djAUkDdkk9HTHX1Jvsidm2r5UaOc3AHJYsn GIWDOT9fM78hYz/ouyodRkImJirjJdE+DEPDc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Ya+CrD6RQ5p1FsGwF6+V+S0eZMj0JP4hh6Oy/+hJ7f4=; b=MwLTASKQBILfCtMePbYOCgrAVTSi/R4hjksajmHQqpMrIrhgFzzUwvI0eiU18eviEQ rCpTeiqY8NQvjO4d6VlJYFhPQ9YEAmRZMcl801BfiKQmnBczQVd0praNgYsuVo3djg9T p129olMYzYhdNlLS+IF3kzykwKNq6IzefC30tgj7KVEOoCecA0rhkyaBq4Ag4g8iTktH lwNMiiBI6w6CJ+sdX7pj5lTqdQpdJjKqXfG/MNEQzIiGzRNWqaxGUgy96pyubjoSIQZQ 5ErqHTJZ1m7bmKL/g2DR6qdixV1Jdh+NV/exMNZ6bFnkTSX5KUoZQbqHuF3cuGUvOSg8 ej0Q== X-Gm-Message-State: ACrzQf337Uy1AwU7M7F2P/eXVmn2HmWQYCHYiwBl6N3Xe0gbajFHp3Vb Cgs07bVrdJga4z/+m2MauR2Z6w== X-Google-Smtp-Source: AMsMyM5g6041duagWXSq4ZLQGnXcqgrjcCpSN7o0m9PhHoi07/8ONF/gpRG29fW+wheHBi3r4stG2w== X-Received: by 2002:a17:902:b20a:b0:178:6f5b:f903 with SMTP id t10-20020a170902b20a00b001786f5bf903mr27366200plr.39.1665526954109; Tue, 11 Oct 2022 15:22:34 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id h9-20020a17090a054900b0020adf65cebbsm86406pjf.8.2022.10.11.15.22.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Oct 2022 15:22:33 -0700 (PDT) Date: Tue, 11 Oct 2022 15:22:32 -0700 From: Kees Cook To: Paramjit Oberoi Cc: LKML , Linux-Fsdevel , Dmitry Torokhov , Anton Vorontsov , Colin Cross , Tony Luck Subject: Re: [PATCH 1/1] pstore/ram: Ensure stable pmsg address with per-CPU ftrace buffers Message-ID: <202210111521.B8D8156490@keescook> References: <20221011183630.3113666-1-pso@chromium.org> <20221011113511.1.I1cf52674cd85d07b300fe3fff3ad6ce830304bb6@changeid> <202210111209.7F1541F5BE@keescook> <202210111302.3179DB77@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Oct 11, 2022 at 01:44:54PM -0700, Paramjit Oberoi wrote: > > > The only downside is it would break some code that works today because > it > > > ran in contexts where the pmsg address was stable (no per-cpu ftrace > > > buffers, or power-of-two CPUs). > > > > I don't follow? And actually, I wonder about the original patch now -- > > nothing should care about the actual addresses. Everything should be > > coming out of the pstore filesystem. > > We are running VMs with the pstore RAM mapped to a file, and using some > tools outside the VM to read/manipulate the pstore after VM shutdown. Ah-ha! Interesting. Well, I think it will be more stable this way even for that. :) -- Kees Cook