Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754614Ab1BMPW1 (ORCPT ); Sun, 13 Feb 2011 10:22:27 -0500 Received: from ka.mail.enyo.de ([87.106.162.201]:48940 "EHLO ka.mail.enyo.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750932Ab1BMPWW convert rfc822-to-8bit (ORCPT ); Sun, 13 Feb 2011 10:22:22 -0500 From: Florian Weimer To: "H.J. Lu" Cc: x32-abi@googlegroups.com, GCC Development , GNU C Library , LKML Subject: Re: X32 psABI status References: <87aai1gdr7.fsf@mid.deneb.enyo.de> <4D5711E0.7020306@zytor.com> <87r5bcnwvw.fsf@mid.deneb.enyo.de> <87tyg8j7le.fsf@mid.deneb.enyo.de> Date: Sun, 13 Feb 2011 16:21:49 +0100 In-Reply-To: (H. J. Lu's message of "Sun, 13 Feb 2011 07:13:57 -0800") Message-ID: <877hd4j6ya.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1810 Lines: 38 * H. J. Lu: > On Sun, Feb 13, 2011 at 7:07 AM, Florian Weimer wrote: >> * H. J. Lu: >> >>>> Actually, I'm wondering if you can do the translation in user space. >>>> There already are 32-on-64 implementations in existence, without >>>> kernel changes (recent Hotspot, LuaJIT, and probably some more). >>> >>> Please check out the x32 kernel source and provide feedback. >> >> I still don't understand why you need a separate syscall table. ?You >> should really be able to run on an unmodified amd64 kernel, in 64 bit > > That is done on purpose. x32 is designed for environments where the > current ia32 API is sufficient. You can think it as ia32 with register > extended to 64bit plus 8 more registers. Everything else is still 32bit. I think of it as amd64 where all the process memory happens to reside in the first 4 GB of address space, and pointers are stored as 32 bits (and you'd also reduce the size of longs because sizeof(long) != sizeof(void *) will break too many programs). As I said, both LuaJIT and Hotspot are already using this model, with custom memory allocators and a user-space translation layers, so I still don't see what you get by changing the kernel. LuaJIT has even implemented the amd64 ABI, so you can call C libraries from your 32-bit code. (Note that LuaJIT uses 64-bit words to store 32-bit pointers with several tag bits, but it does so even on pure 32-bit platforms.) If you want to make x32 closer to i386, I don't see the point. Why would it be problematic if it was as close to i386 as, say, armel? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/