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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 B5B10C282DB for ; Mon, 21 Jan 2019 08:52:15 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 39F0C2084A for ; Mon, 21 Jan 2019 08:52:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 39F0C2084A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 43jlfj0GgDzDqWy for ; Mon, 21 Jan 2019 19:52:13 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=gmail.com (client-ip=209.85.217.65; helo=mail-vs1-f65.google.com; envelope-from=geert.uytterhoeven@gmail.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Received: from mail-vs1-f65.google.com (mail-vs1-f65.google.com [209.85.217.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 43jkws2FW1zDqD8 for ; Mon, 21 Jan 2019 19:19:25 +1100 (AEDT) Received: by mail-vs1-f65.google.com with SMTP id n13so12131335vsk.4 for ; Mon, 21 Jan 2019 00:19:25 -0800 (PST) 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=eNwdIYQYJT6Pc3PhNslPpG4rGotSgFNPjN+8uubEzLc=; b=iZTGoGDnA72iItJgFIySlFB5yOzJWpL8tcskDaOgMRpbIMrkMTDSXnwuJRbG8jFwXi 1Do8SYyVH8GJeamHRdweR7YoXbuRZZUs1VpD8bSUnNHMwDe+jjFimOENrXVnrq/ZYdJ6 KfOMgck08ILvFQoWS9Mx3WtB1muvH7IQ1n/kN4pcuoqRRHWpyEvQWT83dbKXYaJB6hdC Me3s8NF9GV7cR48KdlU/azxwRU+X7I39ClBpx5So2pmEZGZB+ZW8ofj9P5Ikt1xEq5Id XceiM55oGu5hw28aWfGD45G1bAcYDzqvGX/1B9WxC3Q+AIxE1507bbYsRHvu8PL5jdCe sUFg== X-Gm-Message-State: AJcUukdKRu7YI9gBY7c5urXNbw6WIeG7KdKni6tIBGw/YKw1ZDBZJDC+ tqgIsakxkGcjzMSpOnn/qVX4VExTqdnQndWvtpk= X-Google-Smtp-Source: ALg8bN7Na9+3XJsTlxP4CnU3flevzSwRj2I8fvGc/mex1gzD8KE0G4LYkLwzBJ2YcDmVU42ivUABTg84S/YKw2y1uBc= X-Received: by 2002:a67:3885:: with SMTP id n5mr10324892vsi.96.1548058763095; Mon, 21 Jan 2019 00:19:23 -0800 (PST) MIME-Version: 1.0 References: <20190118161835.2259170-1-arnd@arndb.de> <20190118161835.2259170-30-arnd@arndb.de> <20190119142852.cntdihah4mpa3lgx@e5254000004ec.dyn.armlinux.org.uk> In-Reply-To: <20190119142852.cntdihah4mpa3lgx@e5254000004ec.dyn.armlinux.org.uk> From: Geert Uytterhoeven Date: Mon, 21 Jan 2019 09:19:11 +0100 Message-ID: Subject: Re: [PATCH v2 29/29] y2038: add 64-bit time_t syscalls to all 32-bit architectures To: Russell King - ARM Linux admin Content-Type: text/plain; charset="UTF-8" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rich Felker , "linux-ia64@vger.kernel.org" , Linux-sh list , Will Deacon , linux-mips@vger.kernel.org, Max Filippov , Network Development , Deepa Dinamani , "H. Peter Anvin" , sparclinux , linux-arch , linux-s390 , y2038 Mailman List , Helge Deller , X86 ML , Ingo Molnar , Firoz Khan , Catalin Marinas , Matt Turner , Fenghua Yu , Arnd Bergmann , Heiko Carstens , Linux FS Devel , linux-m68k , Andy Lutomirski , Thomas Gleixner , linux-arm-kernel , Michal Simek , Tony Luck , Parisc List , Linux API , LKML , Paul Burton , "Eric W. Biederman" , alpha , Martin Schwidefsky , Andrew Morton , linuxppc-dev , "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Russell, On Sat, Jan 19, 2019 at 3:29 PM Russell King - ARM Linux admin wrote: > On Fri, Jan 18, 2019 at 11:53:25AM -0800, Andy Lutomirski wrote: > > On Fri, Jan 18, 2019 at 11:33 AM Arnd Bergmann wrote: > > > On Fri, Jan 18, 2019 at 7:50 PM Andy Lutomirski wrote: > > > > On Fri, Jan 18, 2019 at 8:25 AM Arnd Bergmann wrote: > > > > > - Once we get to 512, we clash with the x32 numbers (unless > > > > > we remove x32 support first), and probably have to skip > > > > > a few more. I also considered using the 512..547 space > > > > > for 32-bit-only calls (which never clash with x32), but > > > > > that also seems to add a bit of complexity. > > > > > > > > I have a patch that I'll send soon to make x32 use its own table. As > > > > far as I'm concerned, 547 is *it*. 548 is just a normal number and is > > > > not special. But let's please not reuse 512..547 for other purposes > > > > on x86 variants -- that way lies even more confusion, IMO. > > > > > > Fair enough, the space for those numbers is cheap enough here. > > > I take it you mean we also should not reuse that number space if > > > we were to decide to remove x32 soon, but you are not worried > > > about clashing with arch/alpha when everything else uses consistent > > > numbers? > > > > > > > I think we have two issues if we reuse those numbers for new syscalls. > > First, I'd really like to see new syscalls be numbered consistently > > everywhere, or at least on all x86 variants, and we can't on x32 > > because they mean something else. Perhaps more importantly, due to > > what is arguably a rather severe bug, issuing a native x86_64 syscall > > (x32 bit clear) with nr in the range 512..547 does *not* return > > -ENOSYS on a kernel with x32 enabled. Instead it does something that > > is somewhat arbitrary. With my patch applied, it will return -ENOSYS, > > but old kernels will still exist, and this will break syscall probing. > > > > Can we perhaps just start the consistent numbers above 547 or maybe > > block out 512..547 in the new regime? > > I don't think you gain much with that kind of scheme - it won't take > very long before an architecture misses having a syscall added, and > then someone else adds their own. Been there with ARM - I was keeping > the syscall table in the same order as x86 for new syscalls, but now Same for m68k, and probably other architectures. > that others have been adding syscalls to the table since I converted > ARM to the tabular form, that's now gone out the window. > > So, I think it's completely pointless to do what you're suggesting. > We'll just end up with a big hole in the middle of the syscall table > and then revert back to random numbering of syscalls thereafter again. I believe the plan is to add future syscalls for all architectures in a single commit, to keep everything in sync. Regardless, I'm wondering what to do with the holes marked "room for arch specific calls". When is a syscall really arch-specific, and can it be added there, and when does it turn out (later) that it isn't, breaking the synchronization again? The pkey syscalls may be a bad example, as AFAIU they can be implemented on some architectures, but not on some others. Still, I had skipped them when adding new syscalls to m68k. Perhaps we should get rid of the notion of "arch-specific syscalls", and reserve a slot everywhere anyway? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds