From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-6.1 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id E74F07D099 for ; Sun, 20 Jan 2019 16:10:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726749AbfATQKG (ORCPT ); Sun, 20 Jan 2019 11:10:06 -0500 Received: from mail-qt1-f193.google.com ([209.85.160.193]:33919 "EHLO mail-qt1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725985AbfATQKG (ORCPT ); Sun, 20 Jan 2019 11:10:06 -0500 Received: by mail-qt1-f193.google.com with SMTP id r14so20656207qtp.1 for ; Sun, 20 Jan 2019 08:10:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=gJLe9NCacgEEA/W4lTVsKxupjgEOAu7y//ExpgweGGQ=; b=beePmekC5ybj6xweHrQRBJOocc00LddL5ESR8RnA0m0vIJacHdoxDo7u4C8fJvnGws jnWtnziu/4VRu/dl7BRtZuHJbhftt+kmxXRB6qSizh9pkpDzEH/5vbUqhZ6PaYKVGeVb txaZJIlgqQkfQRfL6aEdZQ4jAp3neAfv+oxvU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=gJLe9NCacgEEA/W4lTVsKxupjgEOAu7y//ExpgweGGQ=; b=XXBLb1aEhnxNmsWgOdVGj59cHk5CFh5aY132sDTk4RbD9sNUIIyQvUrsJnvb8jbkZo Q6Fhv72SqjG4Cet5ZJh3hRU80kaSixPXgHZ3nxfkzMwmtSuGEwU3g9XS5Bdz9tlysHFs ZVsWo5kcRQCqsvRligtDODYRKd5y0olbDVKGGScrsVXRWaiqQODHPMZfuEsQnbgeNixx h1x7+t1FXnnPZlrOHRuESEHYNYpU8YQeCEcZOgEgp0WMXSymvbXlrP92YU6Z+NgKLHs5 UKvfnm3Eb7IqhEfZ9NEqvw7jh+smfwg1Ds3ZYQF1heF+A37ityPoV0Rjf4XH2B/FwWJN r8Bw== X-Gm-Message-State: AJcUukf9P7DYQm2rST3EAA645U7inqVTQWw0a8aGaKwtvfESm75xZyET ir9kR0IaDP8iB6JW3vIOuX1kqw== X-Google-Smtp-Source: ALg8bN6KJE00o/malmqZdmRdZvOb/jUIiOlw7+4LQSyoLHCmTbEuruu9Uw2zLVo3FVtldY8C/ppHEQ== X-Received: by 2002:ac8:43d0:: with SMTP id w16mr23699498qtn.78.1548000605188; Sun, 20 Jan 2019 08:10:05 -0800 (PST) Received: from localhost ([2620:0:1004:1100:cca9:fccc:8667:9bdc]) by smtp.gmail.com with ESMTPSA id a17sm55260394qth.93.2019.01.20.08.10.04 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 20 Jan 2019 08:10:04 -0800 (PST) Date: Sun, 20 Jan 2019 11:10:03 -0500 From: Joel Fernandes To: hpa@zytor.com Cc: Greg KH , Christoph Hellwig , linux-kernel@vger.kernel.org, Andrew Morton , ast@kernel.org, atishp04@gmail.com, Borislav Petkov , dancol@google.com, Ingo Molnar , Jan Kara , Jonathan Corbet , karim.yaghmour@opersys.com, Kees Cook , kernel-team@android.com, linux-doc@vger.kernel.org, Manoj Rao , Masahiro Yamada , paulmck@linux.vnet.ibm.com, "Peter Zijlstra (Intel)" , rdunlap@infradead.org, rostedt@goodmis.org, Thomas Gleixner , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , yhs@fb.com Subject: Re: [RFC] Provide in-kernel headers for making it easy to extend the kernel Message-ID: <20190120161003.GB23827@google.com> References: <20190118225543.86996-1-joel@joelfernandes.org> <20190119102800.GB17723@infradead.org> <20190119103606.GA17400@kroah.com> <8BD4CB7A-944C-4EC5-A198-1D85C9EE28D6@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8BD4CB7A-944C-4EC5-A198-1D85C9EE28D6@zytor.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Sat, Jan 19, 2019 at 11:01:13PM -0800, hpa@zytor.com wrote: > On January 19, 2019 2:36:06 AM PST, Greg KH wrote: > >On Sat, Jan 19, 2019 at 02:28:00AM -0800, Christoph Hellwig wrote: > >> This seems like a pretty horrible idea and waste of kernel memory. > > > >It's only a waste if you want it to be a waste, i.e. if you load the > >kernel module. > > > >This really isn't any different from how /proc/config.gz works. > > > >> Just add support to kbuild to store a compressed archive in initramfs > >> and unpack it in the right place. > > > >I think the issue is that some devices do not use initramfs, or switch > >away from it after init happens or something like that. Joel has all > >of > >the looney details that he can provide. > > > >thanks, > > > >greg k-h > > Yeah, well... but it is kind of a losing game... the more in-kernel stuff there is the less smiley are things to actually be supported. It is better than nothing, and if this makes things a bit easier and solves real-world issues people have been having, and is optional, then I don't see why not. > Modularizing is it in some ways even crazier in the sense that at that point you are relying on the filesystem containing the module, which has to be loaded into the kernel by a root user. One could even wonder if a better way to do this would be to have "make modules_install" park an archive file – or even a directory as opposed to a symlink – with this stuff in /lib/modules. We could even provide a tmpfs shim which autoloads such an archive via the firmware loader; this might even be generically useful, who knows. All this seems to assume where the modules are located. In Android, we don't have /lib/modules. This patch generically fits into the grand scheme things and I think is just better made a part of the kernel since it is not that huge once compressed, as Dan also pointed. The more complex, and the more assumptions we make, the less likely people writing tools will get it right and be able to easily use it. > > Note also that initramfs contents can be built into the kernel. Extracting such content into a single-instance tmpfs would again be a possibility Such an approach would bloat the kernel image size though, which may not work for everyone. The module based approach, on the other hand, gives an option to the user to enable the feature, but not have it loaded into memory or used until it is really needed. thanks, - Joel